1vb4

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spinqualitylabelsall models 1vb4, resolution 3.30Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

T=1 capsid structure of Sesbania mosaic virus coat protein deletion mutant CP-N(delta)36

Overview

Sesbania mosaic virus particles consist of 180 coat protein subunits of, 29kDa organized on a T=3 icosahedral lattice. N-terminal deletion mutants, of coat protein that lack 36 (CP-NDelta36) and 65 (CP-NDelta65) residues, from the N terminus, when expressed in Escherichia coli, produced similar, T=1 capsids of approximate diameter 20nm. In contrast to the wild-type, particles, these contain only 60 copies of the truncated protein subunits, (T=1). CP-NDelta65 lacks the "beta-annulus" believed to be responsible for, the error-free assembly of T=3 particles. Though the CP-NDelta36 mutant, has the beta-annulus segment, it does not form a T=3 capsid, presumably, because it lacks an arginine-rich motif found close to the amino terminus., Both CP-NDelta36 and CP-NDelta65 T=1 capsids retain many key features of, the T=3 quaternary structure. Calcium binding geometries at the coat, protein interfaces in these two particles are also nearly identical. When, the conserved aspartate residues that coordinate the calcium, D146 and, D149 in the CP-NDelta65, were mutated to asparagine, (CP-NDelta65-D146N-D149N), the subunits assembled into T=1 particles but, failed to bind calcium ions. The structure of this mutant revealed, particles that were slightly expanded. The analysis of the structures of, these mutant capsids suggests that although calcium binding contributes, substantially to the stability of T=1 particles, it is not mandatory for, their assembly. In contrast, the presence of a large fraction of the, amino-terminal arm including sequences that precede the beta-annulus and, the conserved D149 appear to be indispensable for the error-free assembly, of T=3 particles.

About this Structure

1VB4 is a Single protein structure of sequence from Sesbania mosaic virus with CA as ligand. Full crystallographic information is available from OCA.

Reference

T=1 capsid structures of Sesbania mosaic virus coat protein mutants: determinants of T=3 and T=1 capsid assembly., Sangita V, Lokesh GL, Satheshkumar PS, Vijay CS, Saravanan V, Savithri HS, Murthy MR, J Mol Biol. 2004 Sep 17;342(3):987-99. PMID:15342251

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