]une 7982(2!/j
`
`-, -
`
`I
`r
`
`Vofunu: 3, No. 6
`
`immunology
`today
`
`Receptors, antibodies and disease
`from john Newsom-Davis and Angela Vincent
`
`to
`reported world wide,
`have bee n
`Biochemi sts, endoc rinologi sts immu-
`'
`d G
`d
`nologi.sts a d
`I
`· .
`h'
`I
`I
`()
`t 1e ot 1er ha n
`raves
`<tte.
`n
`.
`·
`n
`neuro ogists s are an
`In terest ·
`11
`111 ce
`di sease (TS I-1-R ant ibody ) and myas-
`surface recep to rs, a s
`·d
`.
`.
`was
`thenia gravis (1\C h-R antibody) are
`evi e nt a t a recent symposium
`held by the C ib a Foundation* When moderate ly prevalent whi le as thma
`these receptors arc target s for auto-
`a nd other atopic disorders (132-adren-
`ant ibod ies
`1
`·
`·
`.
`, e nc ocnne or neuro ogica l
`e rgic- R ant ibody) a re very common.
`1
`d isease ·
`1
`.
`.
`ca n resu t. Attention focussed
`Direct implica tion of the releva nt a nti-
`( R ) for
`part icu lar ly o n receptors
`bodies in the disease process see m s
`thyroid stimulating horm one (TS H ),
`we ll estab lished for most of t he disor-
`Ins uhn , ace tylc holine (1\C h ), prolac-
`ders discussed, a lthough some uncer-
`tin and 132-adre nergic agon ists.
`ta in ty exists abo ut the role of the
`The cli ni ca l importance of auto-
`recent ly
`identifi ed
`132-adrenergic-R
`~ntibod ies to receptors, judged pure-
`a ntibod y.
`Y 111 numerica l te rms, varies con-
`In ast hma a reduction in lung ti ss ue
`1·
`·
`·
`C
`· nsu 111-resista nt diabetes
`Siderab ly
`1
`d
`13, ad re ne rgic receptors, as meas ure
`Insu lin-R a ntibody ), for examp le, is
`by agonist binding or 13 2 re sponses,
`less than SO cases
`ex tremely rare -
`ha s been estab li shed for so me time
`a nd a ntibodi es spec ifi c for
`the
`13 2
`receptor can be ide ntifled either by
`inhibition of agonist binding, by
`immunoprecipita ti on of so lu bi li zed
`(fllliilllll!li fill jJ. 150
`
`·b
`A
`• Rece!Jt
`nt1 odies a nd Disease (Ciba
`ors
`,
`Symposium no. 90) was organized by Dr
`David Evered and cha ired by Professor
`N. /\. Mnchi son. Th e proceed ings wi ll be
`published by Pitm an Medi ca l Ltd .
`
`1. AChR
`
`2. Insulin -A
`
`4. 8 2-adrenergic·R
`
`5.TSH·R
`
`Fig, 1. Diagrammatic representation (roughly to sca le) of proposed subunit
`f
`structures
`f th
`·
`·
`·
`d
`· d'
`·
`1
`·
`d
`b
`hi
`.
`. o
`e prmctpal receptors dtscusse , m
`tcatmg t te stze an num er o
`ndtng Stte( s) for the natural ligand (hatched). Receptors are ranked ( 1-5) acco rdmg
`to the information ava il ab le. Numbers denote the mol. wt.
`
`Transplantation
`Applied wisdom
`from Elizabeth Simpson
`The tradition of an a nnual 'Round Table
`Symposium on Applied Immunology ' was
`its 13th year in 1\xa ms,
`ca rried
`into
`Austria , on 25-27 J a nuary .
`
`On these occasions sma ll numbers
`of clinicia ns and scientists m eet to
`discuss new developments in resea rch
`that have mutu a l interest.
`In
`the opening session on cell(cid:173)
`surface ant igens H. Baine r (Rijsvijk)
`di sc us sed the ln-/!iuo effect of mono(cid:173)
`clona l ant ibodies (M/\bs) directed
`against T-ce ll s ub se ts
`in Rh es us
`monkeys grafted with a ll ogeneic skin.
`The M/\bs defin ed human lympho(cid:173)
`cyte subsets that cross react with the
`equiva lent rhesus monkey cells. Anti(cid:173)
`bodies aga inst
`the help er/induce r
`subse t (O KT4 eq uivalent) prolonged
`skin allograft surviva l whereas those
`d irected aga inst
`the cy totoxic/s up (cid:173)
`pressor subset (0KT8 eq uiva le nt) not
`only failed to prolong surviva l but may
`have shorte ned it. These res ults a re in
`line with rece nt repo rts that in mice
`and rats the T cells involved in initi(cid:173)
`ating gra ft rejection are of th e helper
`(Ly I+ ) phenotype and not the cy to(cid:173)
`(Ly ]+ 2+ ) pheno(cid:173)
`toxic/suppressor
`typ e. D . Arndt-Jovin (Gott inge n) pre(cid:173)
`sen ted her use of sophisti cated physi(cid:173)
`ca l m et hod s
`(Auoresce n ce e n ergy
`transfer,
`rotat iona l diffusion
`and
`translational diffu sion) to assess the
`density, proximity and mobility of
`mou se H-2 (Kk) a ntigens detected
`.with monoclonal a ntibodies. The basic
`info rm at ion obtained
`from
`th ese
`st udies shou ld a ll ow direct examin(cid:173)
`at ion of how H-2 a ntigens ' assoc ia te'
`with suc h extrin sic a ntigens as viruses
`a nd thus the necessa ry co nst ra ints for
`co nsidering the a lte red self versus dual
`receptor hypothes is of T -cel l recep(cid:173)
`tors. P. Peterson (Uppsa la) prese nted
`
`cmztinu!'d rm fJ./51
`
`BIOEPIS EX. 1082
`Page 1
`
`

`

`lmlllllllology Torl11y, 11o/. 3, No. 6, / 1l82
`
`[J (immunology today J
`
`Volume 3, no. 6
`June 1982
`
`Guide for Authors
`A lthnu .~h most of' !rmmmologv Todrzy \ co n(cid:173)
`te nts a re commi ssioned, unsolicited a rticles
`are welcome, preferably a ft er consultation
`With the editori a l offi ce. Authors should be
`awan~ of the diversit y of their readers'
`CXJ)enence of immunology a nd should
`stnve
`to be as widely understood as
`possible.
`Review articles offer a synt h es is of
`current knowl e d gt~ in a field where rapid
`progress has been made. The text shou ld
`not exceed 3000 words, 40 references a nd 6
`fi gures/tables.
`Compass articles a r e c riti ca l co m(cid:173)
`menta ries on one or several recent resea rch
`papers tha t (:ontain res ults of substantial
`;rnportance. The text should not .exceed
`000 wo rds, 15 references and 2 h ~ures/
`tab les.
`·
`Rostrur~ articles offer hypotheses, sta te(cid:173)
`!'TII' hents of persona l op inio n, or speculation.
`. e subJ ec t co nce rn ed need not be
`SCientifi c. The text shou ld not exceed 2000
`words <mel s hou ld be supported by the
`rnm1mum necessa ry number of references
`a nd figures.
`Letters to the Editor offer comme nt on
`a7~t icles rece nt ly pub lished in / mrmmoiogy
`oday or other m atters of concern to its
`Laders. Aut hors should strive to be brief.
`etters should be signed by all named
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`news and features
`
`Receptors, antibodln and dio·ease
`John Newso m-IJa vis and Ange la Vince nt
`Tran.lj!lantalllln: ajijJiiNI wi.1 rlom
`Elizabeth S im pso n
`
`letters
`l nlerleukim : a rose ts a rose.
`Steve n G illis
`
`rostrum
`1.r .1-perm ti?lllllii10.IIlPJm~.\.I'LVe in male lwmo.l'exua!J and
`vaseclrml.i:;,ed men.-1
`Ge ne M . Shea rer a nd Ursul a H urtc nb ac h
`
`compass
`
`The vulnerabiLity oj'1kin grajis to allo- and xeno-rmtibodies:
`a crmwulrwn rr.1olved.-1
`Les li e Hrent
`C:om.jJlenwnt and .1 olubili::.atirm o/ immune comjJiexeo·
`Nev in 1-1 ug hes-J ones
`
`reviews
`Jll/ mwclonal antibodies - lool.r to dis.1erl the nervrmo· sy.rtem
`Colinj. Barnstab le
`The tlzree-dimemlonal stmclure o/ anlibodie.\
`l'vla rku s Marquart and Johann Deise nhofer
`
`The IIWmmary gland m an immmwlogical organ
`I ,ars A. I-ianson
`
`books
`C:ojJ,zng with the !Jimnedical / ,iteralure
`(erl. KennelhS. Warren)
`J ac k Fra nklin
`The lrmnune Syslern . A Crmr.H~ on the AI/ olewlar and
`(,'tflular !Jasii of !mlllllllOlogy ( by I. M r:Crmnefl , A. lvhmro
`and II. Waldmann )
`N . !\.Sta ines
`
`E ditorial O ffi ce :
`J ·~ l scv i cr Bio rn cdi <·;d Press,
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`T el. (0221) 1 15% 1
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`
`technical focus
`
`!ntllllllllllogiml 1'1'11gmt.1·
`
`diary
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`classified
`
`149
`
`149
`
`152
`
`!53
`
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`
`156
`
`!57
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`
`168
`
`172
`
`173
`
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`IV
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`oE! sevier Biomed ical
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`All rights reserved. No part uf rhis publica tion m ay bo reproduced, stored in a retrieval sysram , or transmitt ed in any form or by any means. elec~
`tronic. met:lmnic:al, plloracopying, recording, or oth erwise, without the prior writtt:.'n permission of the copyright owner. S ubmission to this
`joumol of nn article entnils tlw au thor's irrevoco blc and exclusive authorization of the publisher to collect any sums or considerarions for
`copying or t {.'fHOdu c:tion fJayab fe by third parries.
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`De wiled inform ation on co pyright and copyi n ~1 appear s in Immunology Tocllty, M ay 198 1, p. xiv.
`
`BIOEPIS EX. 1082
`Page 2
`
`

`

`160
`
`frmnmwlrJ!',)' Today, vol . .3, Nu. (), !fJ82
`
`The three-dimensional structure of antibodies
`
`l\!Iarkus Marquart and Johann Deisenhofer
`Max-Planck Institut fi.ir Biochemic, Abtcilung Strukturforsclnmg II, D-8033 Maninsriccl, F.R.C.
`
`Antibody molecules arc glycoproteins which occur in
`vertebrate species. They recognize and bind an enor(cid:173)
`mous variety of foreign substances (antigens) and sub(cid:173)
`sequently trigger further defense mechanisms at the
`molecular or cellular
`level. Specific
`recognition
`requires surface structures complementary to the
`antigen and hence a huge variety of antibody
`molecules. In contrast the- effector functions need
`identical interaction sites in all antibody molecules.
`The determination of the primary structure of
`immunoglobulins 1- 1 and the X-ray crystallographic
`studies of several antibody molecules and frag(cid:173)
`ments1·'.7·111·12-1' led to an advanced understanding of
`the way in which antibodies meet these oppoiing
`requirements.
`
`is a schematic drawing of an antibody
`I
`Fig.
`molecule of class I gG I. It is composed of' two idcnt ical
`heavy chains and two identical light chains with mol.
`wts of 50,000 and 25,000, respectively. Both types of
`polypeptide chain arc folded into domains: the four
`domains of the heavy chain arc VH, CII I, Cll2, and
`CH3; the light chain consists of' the two domains VL
`and CL. All domains except CH2 arc arranged in
`pairs which arc held together by non-covalent f'orccs.
`Inter-chain disulfide bridges provide further stability.
`Among antibody molecules of a given class and
`species, the V-domains differ considerably in amino
`acid sequence, whereas the C-domains have identical
`sequences. The V-domains are composed of about 110
`amino acid residues at the N-terrninal end of heavy
`and light chains. The VII-VL pair together forms the
`antigen binding site; different antibody specificities
`arc the result of different amino acid sequences of the
`V-domains. The sequence variability in V-dornains is
`most pronounced in a few hypcrvariable rc!j"ions. On
`the other hand the framework residues arc well con(cid:173)
`served. The constant domains CH2 and CI 13 arc
`involved in effector functions such as cornplcrncnt
`activation and binding to receptors on certain cell
`types. There is significant homolo!j"y between the
`amino acid sequences of all C-domains, and of the
`framework residues of V -domains.
`Proteolytic cleavage at the hin!j"e re!j"ion yields stable
`and functional fragments: the antigen-binding frag(cid:173)
`ment Fab, and the Fe fragment (Fe was 1 he first anti(cid:173)
`body fragment obtained in crystalline forrn) 1'.
`
`A
`
`8
`
`F
`
`E
`
`Fig. 1 Schematic representation of an lgG 1 immunoglobulin
`molecule.
`The arms of the Y-shapecl molecule arc formed by the Fab parts,
`the stern is macle up by the Fe 'part. The light chains arc linked to
`the heavy chains IJy a clisulphiclc bridge close to the C-terrninus.
`The two heavy chains are connectecl via two disulphide linkages in
`the hinge region.
`
`H
`
`G
`
`c
`
`D
`
`X
`
`IMI1UNOGLOBULII< DOI·IAII<S
`IN
`ARRANGEI1EIH OF STflANDS
`X N-TERMINUS UP •• C-TEfU11NU3 UP
`
`Fig. 2 Schematic drawing of the strand topology in a V(cid:173)
`domain viewed parallel to the strands.
`(x) and (e) indicate N-and C-tenninal ends of the strands point(cid:173)
`in~ towards the ob'iervcr.
`
`~ El'il'\'i<"r Bionwdi~.t! P1~'i'i J!JH_?
`II I r, 7-1 '!I 'ljH2jlllll>ll-lllllllljS2. 7.1
`
`This materia I was copied
`at the NLM and may be
`~ubject US Copyright Laws
`
`BIOEPIS EX. 1082
`Page 3
`
`

`

`lrmmmology Today, z•ol. 3, ..Vo. fi, TU82
`
`161
`
`Besides IgG1, several other classes (IgM, IgA, IgD,
`IgE) and subclasses of immunoglobulins have been
`identified; the diflcrcnccs between these arc located in
`the constant region of the heavy chain. The two types
`of light chain (kappa, lambda) can combine with
`heavy chains of any class.
`
`Domain folding
`The general folding pattern in all immunoglobulin
`domains is very similar. It is shown schematically in
`Fig. 2 for a V -domain. The folding is characterized
`by two pleated sheets connected by an internal eli(cid:173)
`sulphide bridge linking strands B and C. The two
`sheets cover a large number of hydrophobic amino
`acid side chains.
`Despite that gross similarity there exist substantial
`differences when one compares V- and C-domains:
`C-domains lack strand X, strand D is very short (2-3
`amino acids) and connected to strand E. In addition
`the length of the loop regions inC-domains is different
`from V -domains, thus changing the overall shape con(cid:173)
`siderably.
`VI-I and VL, on the other hand, show only minor
`differences when comparee! with each other (except in
`the hypcrvariablc regions) as do CL, CHI and CII3.
`CH2 represents yet a
`third
`type of domain,
`differentiated from the other C-domains mainly by the
`branched carbohydrate chain linked to it. It will be
`discussed in more detail below.
`
`Domain-domain interaction
`Two kinds of domain interactions occur in irnmuno(cid:173)
`globulins: lateral (or trans) interactions and longi(cid:173)
`tudinal (or cis) interactions.
`In lateral interactions immunoglobulin domains
`other than CI-12 strongly associate to form modules
`VL-VI-I, CL-CHI, CH3-Cl-13. In V modules VII
`may be replaced by VL to form light chain V dimers
`as seen in the Bcncc-Joncs protein fragments Rei or
`Au 7
`. In Hence-Jones proteins, which arc light chain
`1
`-'
`dimers, one of the light chains simulates the Fab parts
`of the heavy chain, as described for Mcg 111 •
`V modules associate in a different way than C
`modules do. In V modules HGCD faces (sec Fig. 2) of
`the domains get into contact, in C modules the ABFE
`faces arc involved.
`A considerable loss of accessible surface area 11
`is
`connected with contact formation of the immuno(cid:173)
`globulin domains. It amounts to 1760 A2 , 1923 A2 and
`2180 A2 for VL-VH, CL-CH I modules of IgG Kol 12 ·13
`and
`the CH3-CH3 module of an human Fe
`fragmcnt 11 ·1" respectively. In VL-VH association both
`framework residues and amino acids from hyper(cid:173)
`variable segments arc involved. A comparison of V(cid:173)
`domain amino acid sequences of different animal
`species shows that the contacting framework residues
`arc highly conserved. Also
`the constant domain
`residues participating in lateral contact arc either
`invariant or rcplacccl by homologous residues in
`
`different immunoglobulin chains. This low degree of
`sequence variability for the residues important for
`lateral contact formation provides an explanation for
`the fact that different L-chains can associate with
`different H-chains to give intact immunoglobulins.
`In addition to the extensive Van dcr Waals contacts,
`there exist a few trans hydrogen bonds, in which
`mainly polar side chain groups arc involved. There are
`two salt linkages in Kol CL-CI-11 contact: Glu 125
`light chain- Lys 214 heavy chain, Glu 126 light chain
`- Lys 148 heavy chain, which have their analgon in
`CI-13- Cl-13 pairing: Glu 356- Lys 439, Glu 357- Lys
`370.
`CJ-12 is an exception, as it forms a single unit
`without lateral domain interactions (see Fig. 3) *.
`Instead it interacts with bound carbohydrate, which is
`attached to Asn 297. The CI-12 residues that are
`involved in carbohydrate contact arc, with a few
`exceptions, structurally in the same positions as the
`residues that form the CI-B-CI-13 contact (face ABFE
`in Fig. 2). This demonstrates that the carbohydrate
`in CI-12 provides a substitute for
`the C-C con(cid:173)
`tact and presumably helps to stabilize the Cl-12-
`domain. The branched carbohydrate forms a few
`hydrogen bonds with the CI-12-domain, but the dom(cid:173)
`inant interactions are hydrophobic in nature. The
`carbohydrate covers a hydrophobic patch of the
`protein made up of, Phe 241, 243, Val 262, 264, Tyr
`296, Thr 260, Arg 30 I, which would otherwise be
`exposed to the solvent. The loss of accessible surface
`area of one CI-12 domain is 522 A2 , which is only about
`half as much covered surface area as seen in
`CI-13-Cl-13 contact (I 080 A2 ). This observation could
`explain the apparent 'softness' of those parts of the
`CI-12-domain, as seen in the crystal structure 11 ·1 ",
`which are most remote from the CI-13-CI-12 interface.
`The functional relevance of carbohydrate in anti(cid:173)
`bodies is unclear. It might be involved in intracellular
`movements of the glycoprotcins and in secretion 1 r. 1 H. It
`m'ay well be that the origin of the altered functional
`properties of carbohydrate-free antibody variants is
`structural destabilization.
`In contrast to the extensive lateral interactions,
`nonbonded longitudinal interactions along the heavy
`chain or light chain are much weaker or do not exist at
`all. However,
`they arc
`interesting because con(cid:173)
`formational changes in antibodies affect those inter(cid:173)
`actions.
`Fig. 3, which represents the Fe part of an IgG I
`molecule shows the CI-I2-CI-I3 interaction. With a
`loss in accessible surface area of 778 A2 this contact
`has roughly one 'third of the size of CI-13-CI-I 3 contact.
`The residues that participate in CI-12-CI-13 contact
`are highly conserved in all Ig classes, suggesting that
`this contact is likely to be found in IgG and IgA and as
`CI-I3-CI-I4 contact in IgE and IgM.
`
`*Most readers will need a stereo viewer (commercially available)
`to sec in three dimensions the structures shown in the paired
`diagrams on pages 162, 163 and I 66.
`
`This material wascoP"ied
`at the NLM and may bE
`~ubjed USCoP"yright Laws
`
`BIOEPIS EX. 1082
`Page 4
`
`

`

`Fig. 3 Ste reo drawi ng of a s pace
`fillin~ model of human Fc- frag-
`men!.
`I'' o
`Til· · m o k < uk 1 ~ buil t rnlln
`ld t· n t it;il po l) Jl t'Jl! idc c h ; 1i 11~ (t h<lill I .
`1 h;1ir1 2J . an d id!' nti ca l ta rho ll\'c l!·at •·
`c; ro• r p ~. !lo th h;ii \T-; a r·c r·<·I;Jtccl
`ll\
`.rpproxi lll<ll l' d iark
`.
`r• ·rl . I>I<H'k: ( :11 2- dom a in -; or c h ain I
`<t iH i < h; , in 2, I'<" J> <T I ivt l).
`l>l<w . , , .<~ n c; • ·: ( :11 1-d o lna il h a n d <<Jr(cid:173)
`h oh \ dr;11•· o r c hain I ;md chain 2
`r · · · ~ JH T I ivc ly.
`
`Fil{. ·~ II{G I mol ec u le Ko l.
`Tlw l·;d> J> <l rl ' a nd tht· hin t;<' -; ct;llH'Ill <lr•·
`W I' II o rdnn l i 11 1 he Ko l t ry,uli-;, 1 he h p.11 1
`
`',.rJ · \ ' 1.- d o m ;, i 11'
`i>Lar k : ( :1.- rlom; Jilh
`i>lt l< " \ ' 11 -d tlln <Jii h
`: ( :II 1-d tlll'l i! i Jl'i <J lld hi n c;c "'~ ll1 l' J ll
`o r; ,~~ ~ · ·
`
`Fig. 5 Amin o acid co mpa rison of res idu es 98- 119 (E u num (cid:173)
`be ring) of M603, New, Kol a nd Eu h eavy cha in s. T he
`und erli ned res idues were left out in Fig. 6c.
`
`End ofVH
`
`98
`Cys A la A rg
`Cys A la Arg
`Cys A la Arg
`Cys Ala Gly
`
`M603:
`New
`Kol
`Eu
`
`D seg m ent
`
`Asn Tyr
`Tyr
`Asn Leu
`lie
`Asp Gly Gly
`Gly
`Tyr Gly
`
`Gly
`Se r T hr
`A la Gly Cys
`His Gly
`Phe
`lie
`Tyr
`Ser
`
`li e
`Cys Ser Ser Ala
`
`Se r Cys
`
`D l)('
`
`BIOEPIS EX. 1082
`Page 5
`
`

`

`. n bind m g re
`g io n of
`.
`Fig . 6 A ntlge
`
`.
`I G l K ol.
`third h yp er-
`g TI· e exte nded
`c h a m
`(a)
`l
`o f t he heavy
`. ,
`va ria ble loo p
`. b lue a re p t e-
`h D
`!I·'.Iw n tn
`(res idu es c <
`ror by
`l e
`I
`1
`
`coded
`JUl a-
`suma J Y
`1. Ids int o t 1e I
`r ·m e d
`! '''·"'' )
`0
`se<rnle n -
`. d.
`r jJOcket Ol
`"
`· , ·1 b m m g
`)
`. d VH (reel .
`ti ve a n t tget
`.
`b VL (b lac k ) d n
`d siclec ha m s
`kb ne a n
`y
`(
`b) C a b ac o
`. . d ' n a pocket.
`. re n bi ll
`I b
`.
`.
`,
`r K ol a nu g
`, m e·l n tng as
`e t hesa m e
`o
`h
`'
`Colo urs av
`.
`
`1.
`
`in Fi g. 6a._ .· .
`e let io n o r nm.e
`( ·) A ruh c td l d
`I . ·d h y p e t -
`c
`.
`t h e 1 1 11
`.
`·clu es
`In
`,. K o l w hlCl
`rG I
`r es t
`·e rme nt o
`.'
`1
`va n a b le s g u a ll e ngth w tt h lg
`m a kes tl o l e~] d ee . c u rved cl cl't.
`E.u "", reveals <l
`p
`
`)
`
`J segm ent
`
`Gly Pro
`
`Try
`
`Tyr
`
`1 10
`Thr Thr
`Try Gly Ala Gly
`Ph e Asp Val
`Try Gly Gin Gly Ser
`Asp Val
`Leu
`Try Gly Gin Gly Thr Pro
`Asp Tyr
`Pro Glu Glu Tyr Asn Gly Gly
`Leu
`
`119
`Ser Ser
`Th r Val
`Val
`Thr V al Ser Ser
`Va l
`V al Thr Val
`Ser Ser
`Val
`Thr V al Ser Ser
`
`BIOEPIS EX. 1082
`Page 6
`
`

`

`164
`
`!mTmmolot;v Torl(lv, 1'111. ), Xo. li, / 1)82
`
`The CH2-CH3 orientation is found to be somewhat
`variable and influenced by external forces. In the Fe
`fragment crystals the two chemically identical chains
`are in a different environment. As a consequence
`the CH2-CI-13 orientation varies by about 6°. In
`Fc-Protein A complex crystals
`this arrangement
`differs slightly from that ofF c crysta Is 1 1
`.
`More drastic changes are observed in VH-CH I and
`VL-CL longitudinal contacts, when chemically
`different Fab fragments are compared. These
`differences in longitudinal arrangement arc most con(cid:173)
`veniently described by an elbow angle, which
`is
`enclosed by the pseudo diads relating VL to VH and
`CI-I 1 to CL respectively. The elbow angle may vary
`from more than I70° to I35° when we compare Kol
`Fab with McPc Fab 12 ·il.I'J.zo.
`In two cases the elbow angles of the same molecule
`in two different crystal lattices were comparee! and
`found to differ by 8° and 17° rcspectivcly 1
`• In Fab
`'1 ~ 1
`New, with an elbow angle of approximately I37°,
`there exist a few longitudinal contacts between VL
`and CL and VI-I and CH I 22 2', whereas there arc no
`non-bonded longitudinal contacts in intact Kol and
`Fab Kol (sec Fig. 4 ), which arc characterized by an
`open elbow angle. We interpret these observations to
`mean that in Fab Kol the V-C arrangement is flexible
`in solution. In the crystal the molecule is stablizccl by
`packing interactions; these will be discussed from a
`different point of view later.
`
`The antigen-binding area
`Comparison of amino acid sequences of variable
`parts has demonstrated the hypcrvariabili ty of some
`segments. These were considered to be involved in
`antigen binding 21 . I ndccd, crystal structmc anal yscs
`of I g fragment-hapten complexes show that hap tens
`bind in a cleft or depression formed by the hyper(cid:173)
`variable segments.
`The VL dimcr of Rci1·'1 may serve as an illustrative
`example. The symmetrically arranged hypcrvariable
`regions form a deep slit-like pocket around the diad
`relating the two VL monomers. The walls of the slit
`are lined by tyrosincs 49, 9I, 96, Asn 34 and Gin 89;
`the bottom of the pocket is formed by Tyr 36 and Gin
`89. A trinitrophenyl group binds to the Rei fragment
`and fills the binding pocket completely.
`Anoth-er example of an
`IgG fragment-hapten
`complex is Fab New, which is known to bind among
`other ligands a hydroxy derivative of vitamin K 1
`21 .
`The hypervariable segments of New form a shallow
`groove with approximate dimensions of I6 x 7 A and a
`depth of 6 A.
`McPc 603, a mouse IgA (K) Fab fragment 2" binds
`phosphorylcholinc. The site of hapten binding is a
`large wedge shaped cavity, with dimensions IS x 20 A
`and a depth of I2 A. Only five of the six hypcrvariablc
`regions contribute to the formation of the cavity: L(cid:173)
`chain hypcrvariablc regions one and three, and all
`three H-chain hypcrvariablc regions. The second
`hypervariable region of L-chain is screened from the
`
`cavity by the first hypervariablc loop of L-chain and
`the third hypervariablc loop of 11-clwin. The deeper
`cavity in 1\.lcPc(>()3, as cornp;u·ecl to Fab New, is due to
`longer hypervariablc loops. The first hypervariable
`region of L-chain and the third hypervariablc region of
`H-chain
`is
`three residues and the second hyper(cid:173)
`vari<tblc loop of the 11-ch;tin is two residues longer in
`McPcMl3 than in New.
`Phosphorylcholirw occupies only a small part of the
`cavity and intcr;tcts vi;t V;tn dcr \.Y;t;ds forces, electro(cid:173)
`static interactions, <tnd hydrogen bonds with the
`protein.
`In contrast to the above examples Ig(; Kol shows no
`cleft or depression in the antigen-binding region. In
`Ig(; Kol the he;tvy chain h;ts a rather long third hyper(cid:173)
`variable loop, which contains six residues more than
`:\!(>03 <l!ld eight more residues than Fall Ne\\'. The
`;nnino acid -;equcnces of the
`third hypervariahk
`regions of 1\.i(>OV'·. New"\ Kol 2 ' and Eu 2' arc com(cid:173)
`pared in Fi!_j. 5. The sequence ;dignment and cLts-;ifi(cid:173)
`cation in VII, I) <tnd .J segment 2'• 2''
`is sotne\\'hat
`arbitrary, especially for the beginning ofthc.J segment
`as a nucleotide scqttcnce has been clctcrminccl only f(>r
`1\.·1603 21'. The additional residues in Kol with the
`nearly palindromic amino acid sequence _(;Jy-Phe(cid:173)
`Cys-Ser-Scr-/\la-Scr-Cys-Phc-Ciy fold into the puta(cid:173)
`tive antigen binding site <tnd fill it completely (sec Fig.
`C>a,b ). The two cysteins arc disulphidc bridged and
`form the start <tnd endpoints of a short antiparallel [3-
`shcct, comprising residues -Cys-.~cr-Scr-i\.la-Ser-Cys-.
`If in <t model building experiment nine residues arc cut
`from the third hyperva ria hie region of the Kol heavy
`chain, tint'> rna king it of equal lcngt h with l!j(; I Eu-''.
`a deep curved cleft <tppc;trs (Fig. (Jc), which easih·
`could accomrnod;ttc haptcns. \Vith respect to the anti(cid:173)
`~cn binding <tr-c;t lg(; Kol thus looks <ts if it c<HTied its
`own hapten in forrn of an extended third hyper(cid:173)
`variable loop. Another peettli;trity of Ig(; Kol might be
`of interest in that context. In the Kol crystal lattice the
`hypervari;tblc parts of one molecule touch the hin~c
`and spatially adjacent sce;rnents of a symmetrically
`rel<ttcd rnoleculc. This contact consists of three salt
`linkages (Arg 4<) light chain-(:( )()II light chain, :\sp
`SO light chain-1\rg 21 S heavy chain, Asp 53 heil\)'
`chain-Lys I3tt heavy chain), a fcvv hydrogen bonds
`and extensive Van der vVaals interactions. Tints, the
`lattice contact found in Kol crystals might give an
`instructive rnoclcl for antibody-antigen interaction, as
`antigens are usu;tlly rnacrornolecules which cover a
`much larger part oft he ;tntibody than hap tens do.
`
`The hinge segment
`The hinge segment which covalently links Fab and
`Fe parts, has <t unique primary and sp<ttial structure.
`Its central region consists of two parallel disulphiclc(cid:173)
`linkcd poly L-prolinc helices with ;tn ;tmino acid
`sequence -Cys-Pro-Pro-Cys- 12 1 ;. In the Ie;G I subclass
`represented by the Kol molecule the poly-proline
`double helix is short (Fig. 7). llowcvcr, in lg(;3 the
`hine;e sequence is quaclruplicttcc! '" and mock! build-
`
`BIOEPIS EX. 1082
`Page 7
`
`

`

`lrmmmo!ogy Today, uo! . .3, No. fi, f1J82
`
`165
`
`ing suggests that the poly-proFnc segment of this
`molecule may be more than I 00 A long.
`The poly-proline segment, a relatively rigid struc(cid:173)
`ture, is f1anked on both sides by flexible segments: The
`segment on the- N-tcrminal side is well defined in the
`crystal lattice of Kol due to crystal packing inter(cid:173)
`actions, but it lacks intcrr1;1l interactions, that would
`provide stability in solution. The C terminal segment
`is disordered and f1cxible in Kol crystals and in the Fe
`crystal structurc 1l· 1;. The rigid hinge segment allows
`independent movcrnent of the Fab arms and the Fe
`part. There is direct evidence for flexibility in the
`crystal lattice of Kol 111 '1 and Zic 11 . This is in contrast
`to the abnormal IgC protein Dob, which lacks a hinge
`region'"· The significance of the hinge for Fab-Fc
`flexibility is obvious.
`
`Complement binding
`The bindin!j of the Clq component of the Cl
`cornplcx to antigen-antibody complexes is the first
`step
`in
`the classical pathway of complement
`activationllll. The Clq head pieces bind to the CH2
`domains of antibodies li.H,_ Protein A, a constituent of
`the cell wall of .)'1(/jJ!l]'lororms rlltrr:ltl, binds to the Fc(cid:173)
`part of antibody mol~cules of certain classes and sub(cid:173)
`classes, but docs not
`interfere with complement
`binding. The determination of the crystal structure of
`the complex bet ween FB (one of the four Fc-binding
`domains of protein A 17 ) and Fc-fragment showed that
`protein A binds at the CH2-CH3 contact 1 i.lH_ Fig. 8
`shows a space-filling model of the FB-Fc complex.
`The area of CH2 not covered by FB must contain the
`Clq binding site. In view of the size of the Clq head
`pieces (mol. wt 50,000) it appears unlikely that they
`can bind at the inner sides of CII2, i.e. ncar the carbo(cid:173)
`hydrate. The most plausible binding site is therefore
`ncar the tip of CH2 on the outer side of the domain. It
`is worth mentioning that this region is clisorderccl in
`crystals of the FB-Fc complex which indicates that
`this part of the CII2 domain is flexible. Possibly,
`flexibility is required for antibody Clq interaction.
`
`Summary and perspectives
`Investigations of the three-dimensional architecture
`of antibodies have elucidated the folding of the
`polypeptide chains into domains, and the spatial
`aiTangcmcnt of the domains. The structural basis for
`understanding antibody specificity and antibody
`flexibility was obtained. Segmental flexibility is an
`important property of antibodies: Flexible segments of
`the polypeptide chains at the switch and hinge regions
`allow the Fab fragments to change their shape and
`their relative orientation. Conformational changes of
`this kind arc necessary to rneet the geometric require(cid:173)
`ments which <lrise on binding of antibodies to multi(cid:173)
`valent antigens.
`The understanding of the effector functions of anti(cid:173)
`body molecules is much less complete. One of the
`central problems is
`the explanation of the strong
`enhancement of Clq binding to antigen-antibody
`
`complexes as compared to free antibody molecules.
`Two mechanisms have been considered (for a review
`see Ref. 39): since Clq is multimeric with at least six
`antibody binding sites, binding may be enhanced by
`the formation of antigen-antibody aggregates through
`crosslinking. Alternatively, antigen binding might
`induce a conformational change in the Fc-part which
`enhances affinity for Clq.
`There is strong evidence for the importance of
`aggregation, but a mixed mechanism which involves
`aggregation and a conformational change cannot be
`ruled out.
`The studies described here were almost exclusively
`carried out with myeloma or Bcncc-.J ones proteins
`because these were the only homogeneous immuno(cid:173)
`globulins which could be obtained
`in sufficient
`quantity. However, in most cases the specificities of
`such molecules is unknown. Recently, large amounts
`of homogeneous antibodies elicited against strepto(cid:173)
`coccal or pneumococcal polysaccharides became
`available from certain rabbit and mouse strains1 11 11_
`These sources, and the usc of hybrids obtained from
`myeloma and spleen cells have made it possible to
`obtain homogeneous antibodies of defined speci(cid:173)
`ficity12·11. Structural studies of 'natural' antigen-anti(cid:173)
`body complexes can be expected to lead to a rnorc
`complete understanding of antibody
`function.
`Crystallographic work on a specific a