Morphological proteins of phage lambda: Identification of the major head protein as the product of gene E

Abstract

Phage λ dissociates in boiling SDS into at least three major and three minor proteins, which separate from each other in gel electrophoresis. By joining, in vitro, radioactive heads to nonradioactive tails, and vice versa, and by purifying the resulting complete phage particles it was possible to identify three of the proteins as constituents of the head and three of the tail. The major head protein has a molecular weight of 38,000 and accounts for 60% of the total protein mass of the phage particle. This protein appears to be the product of gene E because it is absent from extracts of induced lysogenic bacteria carrying a susE− prophage, but is present in extracts of lysogens for sus (amber) mutants in any of the other known head genes: A, W, B, C, D, or F. Petit λ, a form of the λ head which lacks a tail and contains no DNA, is also an assembly of the major head protein. However, purified petit λ lacks the second most abundant protein of complete heads which has a molecular weight of 12,000.