PDBsum entry 1bmu

Hydrolase

PDB id

1bmu

Contents

			Protein chain

					214 a.a.

References listed in PDB file

Key reference

Title

Crystal structures of ms2 capsids with mutations in the subunit fg loop.

Authors

N.J.Stonehouse, K.Valegård, R.Golmohammadi, S.Van den worm, C.Walton, P.G.Stockley, L.Liljas.

Ref.

J Mol Biol, 1996, 256, 330-339. [DOI no: 10.1006/jmbi.1996.0089]

PubMed id

8594200

Abstract

The loop between the F and G beta strands (FG loop) of the bacteriophage MS2 coat protein subunit forms inter-subunit contacts around the 5-fold and 3-fold (quasi 6-fold) axes of the T=3 protein shell. In capsids, the loop is found in two very different conformations, one in B subunits, which form the 5-fold contact, and one in A and C subunits, which form the quasi 6-fold contact. One proline residue, Pro78, is strictly conserved in the coat protein of all related bacteriophages, and in the case of MS2 this proline residue is preceded by a cis peptide bond in the B subunit. In order to probe the role of the FG loop in capsid assembly, we have determined the crystal structures of two MS2 capsids, formed by coat proteins with mutations at two positions in the FG loop, P78N or E76D. These mutants show conformational changes in the FG loops that explain the reduced temperature stability of the capsids. The P78N mutant has a normal trans peptide bond at position 78.



	Figure 2. Figure 2. Schematic drawing of six coat protein subunits. The three independent subunits A, B and C making up one asymmetric unit of the icosahedron are drawn with black lines, and the three subunits A', B' and C' completing the dimers are shown in grey. At the 3-fold and 5-fold axes, the FG loops of all interacting subunits are shown. The position of the 3-fold and 5-fold axes are each shown with a stick. A drawing of an icosahedron in the same orientation is shown (inset). The drawing was made using the program MOLSCRIPT (Kraulis, 1991).

PROCHECK

	Headers