A three-dimensional cryo-electron microscopy structure of the bacteriophage phi KZ head

Abstract

The three-dimensional structure of the Pseudomonas aeruginosa bacteriophage Phi KZ head has been determined by cryo-electron microscopy and image reconstruction to 18 (A) over circle resolution. The head has icosahedral symmetry measuring 1455 (a) over circle in diameter along 5-fold axes and a unique portal vertex to which is attached an approximately 1800 (A) over circle -long contractile tail. The 65 kDa major capsid protein, gp120, is organized into a surface lattice of hexamers, with T=27 triangulation. The shape and size of the hexamers is similar to the hexameric building blocks of the bacteriophages T4, Phi 29, P22, and HK97. Pentameric vertices of the capsid are occupied by complexes composed of several special vertex proteins. The double-stranded genomic DNA is packaged into a highly condensed series of layers, separated by 24 (A) over circle, that follow the contour of the inner wall of the capsid. (c) 2005 Elsevier Ltd. All rights reserved.