Lattice Transformations and Subunit Conformational Changes in Phage Capsid Maturation

Abstract

A general feature of the pathways for the assembly of double-stranded DNA phages and viruses is the assembly of coat and scaffolding subunits into a precursor shell or procapsid, followed by packaging of the genomic DNA into the shell. Coupled to this DNA packaging process is the loss of the scaffolding subunits and expansion and re-organization of the procapsid lattice to the lattice of the mature virus. Such lattice transitions have also been observed with adenoviruses and herpesviruses. In re-organizing into the mature capsid lattice, each subunit of the precursor lattice must change its conformation, or its relationship with its neighbours, or both. We briefly review here recent structural data for phages P22 and HK97, and describe the motions and conformational changes associated with this lattice transition. Possible functions of such constrained transformations within the virus life-cycle are discussed.