"The structure of collagen"

Date:
1955
Reference:
PP/CRI/I/1/8
Catalogue details

Licence: In copyright

Credit: "The structure of collagen". Source: Wellcome Collection.

    1/3
    {Reprinted front Nature, Vol. 176, pp. 915-916, Nov. 12, 1955) THE STRUCTURE OF COLLAGEN By Dr. ALEXANDER RICH* and Dr . F. H. C. CRICK Medical Research Council Unit for the Study of the Molecular Structure of Biological Systems, Cavendish Laboratory, Cambridge ERY recently, Ramachandran and Kartha 1 have made an important contribution by proposing a coiled-coil structure for collagen. We believe this idea to be basically correct but the actual structure suggested by them to be wrong. Their structure consists of three polypeptide chains, each having approximately a three-fold screw axis. In addition, the chains slowly wind around each other to form a coiled coil, thus reproducing the observed non-integer screw axis 2 . The major helix is right- handed, the minor one left-handed. Each chain is held to its neighbours by two sets of systematic hydrogen bonds. The allowed sequence of residues is —G—R—P—G—R—P—, etc., where G implies glycine only, R implies any residue except proline or hydroxy proline, and P implies any residue, but usually proline or hydroxy proline. We believe this structure to be wrong for two reasons. (1) It is stereoqhemically unsatisfactory. In particular, there is a very short C a —C a contact of 3-3 A. (normally 3-6-4-0 A.) and an extremely short C a —O contact of 2-6 A. (normally 3-2-3-5 A.). In addition, the hydrogen bond angles are on the out side limit of the values usually found. (2) It is not compatible with recent work 3 on the amino-acid sequence, which shows that is a common sequence in collagen. On the other hand, Dr. Pauline Cowan and her co-workers 4 have informed us that a preliminary optical diffraction pattern of this structure agrees qualitatively with the observed wide-angle X-ray, pattern of collagen. They have also pointed out to us that the configuration of the backbone of the polypeptide chain is similar to that found by them for polyproline 5 . These facts suggest that the struc ture, though incorrect, is on the right general lines. Our own work on collagen has sprung from our * Permanent address : Physical Chemistry Section, National institute of Mental Health, Bethesda, Maryland. -g!y—pro-—hypro—