Crystal structure of the collagen triple helix model [(Pro-Pro-Gly)10]3

The first report of the full-length structure of the collagen-like
polypeptide [(Pro-Pro-Gly)(10)](3) is given. This structure was obtained
from crystals grown in a microgravity environment, which diffracted up to
1.3 A, using synchrotron radiation. The final model, which was refined to
an R(factor) of 0.18, is the highest-resolution description of a collagen
triple helix reported to date. This structure provides clues regarding a
series of aspects related to collagen triple helix structure and assembly.
The strict dependence of proline puckering on the position inside the
Pro-Pro-Gly triplets and the correlation between backbone and side chain
dihedral angles support the propensity-based mechanism of triple helix
stabilization/destabilization induced by hydroxyproline. Furthermore, the
analysis of [(Pro-Pro-Gly)(10)](3) packing, which is governed by
electrostatic interactions, suggests that charges may act as locking
features in the axial organization of triple helices in the collagen fibrils.