Identification of early proteins coded by bacteriophage P22

Abstract

Twelve early proteins coded by phage P22 have been resolved by sodium dodecyl sulfate-polyacrylamide-gel electrophoresis of labeled infected cell lysates. Four early gene products, those of genes 12, 17, int, and erf, was identified by their absence in amber mutant-infected lysates. Several additional nonessential proteins were identified by their absence from lysates of cells infected with a deletion mutant, bp5, which is missing a portion of the early region of the chromosome. Mutations in genes 12 and 23 prevent normal expression of the phage-coded late proteins, and a mutation in gene 24 prevents expression of early and late protein synthesis. These last findings support the notion that P22 protein synthesis is controlled by two sequentially acting positive regulation elements, the products of genes 24 and 23, which serve functions analogous to the gene N and Q proteins of phage λ.