Precursors of the T4 internal peptides.

The precursors of the two T4 internal peptides have been identified by in vitro cleavage of individual phage proteins eluted from sodium dodecyl sulfate-acrylamide gels. The precursor of internal peptide VII is p22, the product of T4 gene 22 and an essential component of the morphogenic core. The precursor of peptide II is a protein with a molecular weight of approximately 13,000, whose gene has yet to be defined by mutation. A newly detected protein of approximately 15,000 molecular weight is found to be cleaved and is, therefore, likely to be a component of precursor head structures.