| Autor: |
R.D.B. Fraser, E. Suzuki, T.P. MacRae |
| Rok vydání: |
1976 |
| Předmět: |
|
| Zdroj: |
Journal of Molecular Biology. 108:435-452 |
| ISSN: |
0022-2836 |
| DOI: |
10.1016/s0022-2836(76)80129-5 |
| Popis: |
The fine detail in the X-ray diffraction pattern of α-keratin has been explored out to spacings of 4 A by a direct mapping of the cylindrically averagedintensity transform. The meridional maxima lie on a set of layer lines corresponding to an axially projected repeat of structure of 470 A, and the distribution of nonmeridional maxima is consistent with a helical symmetry in which the basic helix has a pitch † of ±3447 A, and a line group which does not involve a rotation axis parallel to the screw axis. In addition, there is evidence for a pseudo repeat with a unit height of 67·1 A and a unit twist of ±109·9° associated with the coiled-coil rope segments that are believed to constitute the framework of the microfibril. Possible packing arrangements of the coiled-coil rope segments within the pseudo repeat have been analyzed and two models derived; the first is based on 2-strand rope segments in which the major helix of the coiled-coil has a pitch of −151 A and the second is based on 3-strand rope segments in which the major helix of the coiled-coil has a pitch of −220 A. Inter-rope contacts in the two models have been analyzed, and these can be correlated with the distribution of amino acid residues in the sequences of helical segments isolated from the low-sulphur wool proteins. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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