Protofilament atomic structures

The atomic structure of tubulin protofilaments (Figs. 3 and 4) is known from 3.5 A resolution maps, the first of which came from electron crystallography of zinc-induced 2D sheets (Nogales et al., 1998b), subsequently refined (Lowe et al., 2001). Recent data, including important information... 

Li L, Darden TA, Bartolotti L, Kominos D, Pederson LG. An atomic model for the pleated beta-sheet structure of Abeta amyloid protofilaments. Biophys J 1999 76 2871-2878. 

Figure 18 Structural model for A0 (1-40) protofilaments, derived by energy minimization with constraints based on solid-state NMR data, (a) Ribbon representation of residues 8-40, viewed down the long axis of the protofilament, (b) Atomic representation of residues 1-40. From Ref. 141.

The first near-atomic resolution structure of the tubulin dimer was determined from a 3.7-A electron density map obtained by EC from the two-dimensional, crystalline sheets of tubulin that form in the presence of Zn ions and PTX [11], This polymerized form of tubulin consists of protofilaments arranged in an antiparallel way, while protofilaments are parallel in genuine MT. Despite this different orientation of adjacent protofilaments, 3D reconstruction of intact MT from cryoelectron microscopy images at 20 A or 8 A resolution demonstrate that the conformation of tubulin is... 

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