title: A new model for packing of type-I collagen molecules in the native fibril.
abstract: A specific fibril model is presented consisting of bundles of five-stranded microfibrils, which are usually disordered (except axially) but under lateral compression become ordered. The features are as follows (where D = 234 residues or 67 nm): (1) D-staggered collagen molecules 4.5 D long in the helical microfibril have a left-handed supercoil with a pitch of 400-700 residues, but microfibrils need not have helical symmetry. (2) straight-tilted 0.5-D overlap regions on a near-hexagonal lattice contribute the discrete x-ray diffraction reflections arising from lateral order, while the gap regions remain disordered. (3) The overlap regions are equivalent, but are crystallographically distinguished by systematic displacements from the near-hexagonal lattice. (4) The unit cell is the same as in a recently proposed three-dimensional crystal model, and calculated intensities in the equatorial region of the x-ray diffraction pattern agree with observed values.
mesh_terms: D000818:Animals; D003094:Collagen; D008958:Models, Molecular; D008961:Models, Structural; D009210:Myofibrils / Q000648:ultrastructure*; D011487:Protein Conformation; D051381:Rats; D013710:Tendons / Q000648:ultrastructure; D014961:X-Ray Diffraction
chemical_list: D003094:Collagen