Bacteriophage MS2 is an icosahedral virus with 180 copies of a coat protein forming a shell around a single-stranded RNA molecule. The coat protein subunits form a lattice with the triangulation number T = 3. The coat protein has a fold which is diff ...
Bacteriophage MS2 is an icosahedral virus with 180 copies of a coat protein forming a shell around a single-stranded RNA molecule. The coat protein subunits form a lattice with the triangulation number T = 3. The coat protein has a fold which is different from the fold of all other viral coat proteins so far known. It consists of a five-stranded beta sheet facing the inside of the particle, and a hairpin and two helices on the outside. The crystal structure has been refined at 2.8 A resolution. The final R-factor was 0.189 for reflections with F > 2 sigma, and the root-mean-square deviation from idealized bond lengths and bond angles was 0.015 A and 2.9 degrees, respectively. The three chemically identical conformers A, B and C are largely similar. The B conformer has a unique conformation in one loop, which is involved in 5-fold interactions, while the A and C conformers, which are involved in the quasi-6-fold contacts, are similar throughout the structure. One cis-proline has been identified in the B conformer but the corresponding prolines in A and C are of the trans isomer. This residue is conserved within small RNA coliphages and it is proposed that this isomerization enables a less elongated loop (FG) around the 5-fold axis, thus creating a channel. The extensive dimer contact supports the idea of dimers as initial building blocks. An assembly pathway is proposed where five dimers converge into a pentamer and 12 pentamers are linked together with free dimers creating a complete particle.
Related Citations:
The Structure of Bacteriophage MS2 Liljas, L.,Valegard, K. (1990) Semin.Virol. 1: 467
Purification, Crystallization and Preliminary X-Ray Data of the Bacteriophage MS2 Valegard, K.,Unge, T.,Montelius, I.,Strandberg, B.,Fiers, W. (1986) J.Mol.Biol. 190: 587
Structure Determination of the Bacteriophage MS2 Valegard, K.,Liljas, L.,Fridborg, K.,Unge, T. (1991) Acta Crystallogr.,Sect.B 47: 949
The Three-Dimensional Structure of the Bacterial Virus MS2 Valegard, K.,Liljas, L.,Fridborg, K.,Unge, T. (1990) Nature 345: 36
Organizational Affiliation:
Department of Molecular Biology, Uppsala University Uppsala Biomedical Centre, Sweden.
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