ON THE STRUCTURE OF THE SCAFFOLDING CORE OF BACTERIOPHAGE-T4 AND ITS ROLE IN HEAD LENGTH DETERMINATION

The scaffolding core in bacteriophages is a temporary structure that p lays a major role in determining the shape of the protein shell that e ncapsulates the viral DNA. In the currently accepted structure for the scaffolding core in bacteriophage T4, there is a symmetry mismatch be tween the protein shell, which has fivefold symmetry, and the scaffold ing core, which is believed to consist of six helical chains. Alternat e structures for the scaffolding core in T4 are investigated. Starting with the hypothesis that the shell and a 10-helix core would have mat ching symmetry, a Vernier mechanism is proposed that explains the prev iously unexplained behavior of the length determination process in gia nt head mutants of T4. Other possible Vernier mechanisms for core stru ctures containing six and eight helices are also explored. (C) 1998 Ac ademic Press.