Primary structure of the phage P22 repressor and its gene c2

The amino acid sequence of the Salmonella phage P2 repressor and the DNA sequence of its gene c2 have been determined. Sequential Edman degradations on intact P22 repressor and repressor peptides generated by proteolytic and chemical cleavages have been overlapped to give approximately 97% of the complete protein sequence. Additionally, the nucleotide sequence of the P22 c2 repressor gene has been determined by DNA sequencing techniques. The DNA sequence and partial protein sequence are collinear and together define the complete amino acid sequence of P22 repressor. The repressor is a single-chain 216 amino acid polypeptide. Basic residues in the sequence tend to be clustered, and residues 9-20 are highly basic, containing five arginyl and three lysyl residues. The carboxyl-terminal 133 amino acids of the c2 repressor are homologous to the carboxyl-terminal sequence of the coliphage lambda cI repressor. The amino-terminal sequences of these two repressors show little similarity.