Lambdoid Phage Head Assembly

Abstract

… the order and size of all the planets and spheres and heaven itself are so linked together that in no portion of it can anything be shifted without disrupting the remaining parts and the universe as a whole . Copernicus: De Revolutionibus INTRODUCTION In bacteriophage morphogenesis, macromolecules are assembled into complex, elegant structures. The architecture of the finished virion is determined both by the characteristics of the structural proteins themselves and by the influence of other viral and host proteins that participate transiently in the assembly process. The interactions among these components can be dissected by physical and chemical analysis of purified viral proteins, assembly intermediates, and completed virus particles, as well as through genetic studies. Bacteriophage λ morphogenesis is a model for macromolecular assembly in general, because the virion is a relatively simple, well-defined structure that consists of a limited number of components and because the λ -Escherichia coli system is well understood and easily manipulated. An additional positive feature is the existence of related lambdoid phages (including Salmonella phage P22), whose morphogenetic pathways can be compared with that of λ to help derive information about evolutionarily conserved and variable elements in morphogenesis. Much progress has been made since Kellenberger and Edgar (1971) discussed λ assembly in The Bacteriophage Lambda. We now know that the steps in bacteriophage λ head morphogenesis generally proceed in an obligate order, so that phage-coded proteins (with the help of the bacterial groEL - and groES -gene products) assemble into small aggregates, form large precursor structures called...