The structure of collagen, A Rich, F Crick

Tags: hydrogen bonds, ALEXANDER RICH, Ramarch Coumil Unit, hydrogen bond, structure, glycine, space group, Careful structure, amino-acid sequence, polypeptide chain, hydroxyproline, DR F. H. C. CRICK
Content: NO.4408 November 12, 1955 NATURE
By DR. ALEXANDER RICH* and DR F. H. C. CRICK Medial Ramarch Coumil Unit for tha Stud of the Modular Strutturn d Blofoglal Systems, Cavendish Lato ratory, CombrIdge
ERY recently, Bsmachsndran end Karths' have
Both 6tNCtlX'C I and structure D will accommodate
mede an importent contribution by proposing a the sequence
c&d-coil tin&m for c~Uegen. We belier this j&e to be bssically correct but the actual structure
euegcsted by them to be wrong.
but they do so in 8 di%rent manner. In structure II
Their structure consists of three palypeptide ~hsh~, the glycine position is nom the tube, end every third
as& having 8pprOrimk&td3' 8 three-fold screw axis. residue must be glycine. The proline and hydroxy-
h addition, the &sins slowly wind around each other proline pcsitions, on the other hand, w far mxn~ved
to form e c&led coil, thue mproducingthe obeerved from the t&s. Either proline or hydxmypmline can
non-integer screw aria*. The major helix is right- go into either position-there see&4 to be no pm-
handed, the minor one 1efManded. Bach &sin is fered
in neither case can the OH of hydroxy-
held to ib neighbcura by tt~ sets of e-tic
proline make a hydrogen bond wi4h e CO group of
hydrogen bon&.
an adjacent chsiu within the same set of three ch&ns.
The allowed sequence of reoiduee is
~tNctUI'f3 1 Will dt3C 8CCOI.XbUkOd8tC thC 8bOVE3
sequence; but when the hydroxyprolii is in the expected position (that is, previous to glycine) its
where C implies glycine only, R implies any residue OH group m form 8 hydrogen bond to one of the
except proline or hydroxyproline, and P implies any adjacent ch&ns within the me set. Careful structure
&due, but ususlly proline or hydroxyproline.
building hee ahown that not all the possible pcsitions
Iire believe this structure to be wrong for two for hydroxyproline can he occupied if the &ucture
reasons. (1) It is stereochemically unsati&ctory. In is to fit together comfortably. This is compatible
pnrticulw, there is 13very short Csc, contact of with the amino-acid snslys~ of collsgen, which show
3.3 A. (normally 34-4-O A.) and an extremely short thst the amount of hydroxyproline present in bovine
G-0 contact of 26 A. (normslly 32-34 A.). In collagen' would 611 about one-third of these sites.
addition, the hydrogen bond angles are on the out- The polypeptide backbones, being held together by
rcidolimit of the values usuelly found. (2) It is not oniy one set of hydrogen bonds, have 8 certain
compatible with recent work* on the amino-acid amount of flexibilitv. In the undeformed'structure.
sequence, whioh shows t.hat
only glycine can 63 8ccommod8ted in the glycine
sitee. However. if the structure is Morn& somewhat, them sit& can accommodste other residues,
is 8 common sequence in collegen.
though only to 8 iiited extent. This m8y explaiu
On the other hand, Dr. Perrline Cowan snd her ccwtain minor feetures of the amino-acid sequence
co-worka* have infanned us that 8 preliminsry d&8.
optic44 diffmction p&tern of thii structure agrees We have made an exhaustive study of all poeaible
qualitatively With the obemved Wide-angle X-my strllctm (using tcpologicul enu?ner8 tion, simihu to
pettern of adagem. Thy have &O pointed out to t&et of Brsgg, Kendrew end Per&a) of this general
WI that the canflgnretion of the. bsckbone of the type which are compatible with the observed mrew
polypeptide chain is similsr to th& found by them da-that is, with thme parallel chin lit&d by at
for p~lypmliae~. Theee fect.6suggeut that the &NC- least one systematic set of hydrogen bonds-and we
ture, though incorrect, ie on the right geneml lines. find that : (1) no Btructure with &JO system&o set8
of hydrogen bonds is stereochemically pcssiile;
rfxent structure for polyglycine II *. We have t&m (2) no other structure with one systematic set of
a ccmpact group of three ndjacent ch&s out of the hydrogen bonds is stereocbemically sstisf'ory
polyglycine lattice (Space Group P 3,) and twisted except the two described above derived from poly-
them, 8s in the PRmeahendrarr-Kerthe Bt~cture, to glycine. Neither were w ehIe to add occ&onal
form e &m&w coiled coil. Such e Group Csu be backbone hydrogen bonds to structures I and II in
selected in two d&rent weys, since the metry
is 8 convincing manner.
brigrmsl, not hexsgonal. We have adled the two
All the above findings arE Independent of a&u-
resulting arraugementsatructureI and structureIf. mente about the aide-chainaranpments. We
Both have a right-handed major helix and e left- therefore conclude that t3tNCtAUH
I end II, though
handed minor helix. srmnged to fit the ohserved making few hydrogen bonda tptamaMy, are the
non-integer screw. Both have only one set of system- be& that can be eohieved clang thy line+ Note
atic hydrogen bonds linking neighbouring chains. In thet, 86 in. polyglycine II*, it is not unpasslble th8t
nt~ructure I the NHgroups point anticlockwise when th;ehCon
of one of the three ohaim may be
viewed from the carboxyl ends of the c~18im5'; in
RtNCtIUFi n ~b&WilH3.
Pmlim'inary work on the optical Mns&me of
These two structures am thus similsr to th8t of theee tw etruoturee (tmrried out with Dr. A. Elliott
Ramachandran and Kartha in being three-chain on his optical trsnsform machine) show h&h strut-
COiiCd-COil &~t?tUree : but they differ in having Ody turee to give Nugh E?tgmmmt with the x-rqr
one set of svstematic hydrogen bonds instead of two. pattern, though structure II shows a diserep~oy on
~Moreovec, they are both stereochemically completely the fourth leyer-line. Both struotums M &o corn-
putible with the in&~&a observ&ions. Further
Psr tuta
msnent a of afent
ddrem: 4.El dth.
Phymlal Bathada
work will therefore he required them. We BIW at the moment
to de&de hetweea inchned to bvour
November 12, 1955 vOL. l76
fitruoture I, a
it m8kea &%&ive and eysMm8Uo
um of the hydroqqwoline raaidueo. "+avam;*t presented extenrtive evidemx mqgaamg
unusu8I 8minoaoid etebiliza f&e oollagen &uoture. wefeelth8tthisiaulorelikelytotak6placeby form8tion of hydrogen bon& within 8 group of three ch8iM th8n between cli&mnt group3 of cheins? In addition, &nIoture I expl8imJ in 8 n8tur8l way the amino-a&d sequence date. !l!hua while the peptide
hypro-gly is common, gly-hypro ie not found. Simihuly, @y-pro is common, where& pro-gly is r8re.
In etructure I this preference ia expLained in terma of
fhehydroxyproiine-hydrogenbondbetweentheoheias. >+Uthough we 08nnot et the moment m8ke 8
ihl8l decision
the two l#euam%
we think
it very probable that one of them ie correot (or, lees
likely, both). The general agreement with the X-ray
pattern, the close reeemblence to polyproEne snd to polyglycine II, ard the ability to erpl8in the major
features of the amino-acid eequence dete all suggwt
that [email protected] h 8 8t?U~Ul'9 Of thifl type ; th8t ie, 8
three-chain, sptematic
coiled-coil hydrogen
with one set of
`likel to th8llk Dr. A Elliott for l.&
8~91~t~pc8 in obt8iniig the optial transforms.
roct. 10
0. N.. md X&h. 0.. Ndun. 1% 693 iigs),
' cob8o. a. and Bear a 8. J. A-. ulrr. 800. 78. 27f3 (lQ&)
Cow8o.k Bl., NO&. 8odstnuttMeofcollagw"
hattn8drwBuw~d8Llnl. odJu.
"Tlw N& lOtJ)* w
In "Flbrona Proteiru and dbe1r Blolqdul S&cnncc" &c lk&. BloL syrup.. 9 w8lub. Univ. Plah 1955). Dew. IL s.; .
`Pmauml oommwlutloo.
Alau aommuolc8tad 8t the Snl later.
o8tlowl Cunmn of Blocbwnlrtn. Bmmcls. 1955.
'COM, P. N.Li,nd xd38v4 8., N&w, 11). ii01(1956).
' W F. H. Q. aml Blab. A., Ndn, 178,180 (19m.
' Born*. J. H.. aad Kenton. B. H.. B&&m. J.. U 9K8 119~.
PtmS M. F.. Proc. Rag. k.,
" t3~tmon, K. Il.. Nutuw. 175, 70 (1956).

A Rich, F Crick

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