Primary structure of the phage P22 repressor and its gene c2

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Abstract
The amino acid sequence of the Salmonella phage P22 repressor and the DNA sequence of its gene c2 were determined. Sequential Edman degradations on intact P22 repressor and repressor peptides generated by proteolytic and chemical cleavages were overlapped to give .apprx. 97% of the complete protein sequence. Additionally, the nucleotide sequence of the P22 c2 repressor gene was 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 5 arginyl and 3 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 2 repressors show little similarity.