Recombinant portal protein fromStaphylococcus epidermidisbacteriophage CNPH82 is a 13-subunit oligomer

Abstract

The portal protein cn3 of bacteriophage CNPH82 is predicted to serve as a gateway for translocation of viral genome into preformed pro-capsid, like portal proteins from other double-stranded DNA tailed bacteriophages. The host of bacteriophage CNPH82 is the opportunistic human pathogenic bacterium Staphylococcus epidermidis, a major cause of nosocomial infections. The portal protein of this phage has been cloned, overexpressed and purified. Sizeexclusion chromatography-multi-angle laser light scattering analysis has indicated that the portal protein contains $13 subunits. Crystals of the portal protein, diffracting to 4.2 Å , have been obtained. These crystals belong to the space group C222 1 with the unit-cell parameters of a = 252.4, b = 367.0, c = 175.5 Å . The self-rotation function revealed the presence of a single 13-subunit oligomer in the asymmetric unit.

12-Fold symmetry of the putative portal protein from theThermus thermophilusbacteriophage G20C determined by X-ray analysis

“…Following heterologous expression, however, viral portal proteins have been found to display 11-fold, 12-fold, 13-fold or 14-fold symmetry (Trus et al, 2004;Rao & Feiss, 2008). For example, the SPP1 and CNPH82 portal proteins exhibit 13-fold symmetry following heterologous expression in Escherichia coli (Lebedev et al, 2007;Lurz et al, 2001;Luan et al, 2012). This suggests that dodecamers may be selected for, or their assembly may be promoted, during the native oligomerization process and that the dodecameric arrangement of the portal protein is important for its function (Rao & Feiss, 2008;Lurz et al, 2001).…”

“…Despite the portal proteins from different tailed bacteriophages varying significantly in both amino-acid sequence and molecular mass, they all assemble into circular homo-oligomers that have a turbine-like shape and contain a central channel for DNA translocation (Luan et al, 2012;Orlova et al, 1999). The X-ray structures of several bacteriophage portal proteins subsequently revealed additional common structural features and shed light on the mode of action of the portal proteins (Lebedev et al, 2007;Olia et al, 2011;Simpson et al, 2001).…”