An E. coli gene coding for a protamine-like protein

Several open reading frames exist in the region of the tRNA₁ ^Tyr gene of the E. coli genome. One such sequence encodes a polypeptide 33 amino acids in length that, on the basis of size and amino acid sequence, bears a striking resemblance to the protamines found in trout sperm. DNA from the transducing phage φ80 tRNA₁ ^Tyr su3⁺ directs in vitro synthesis of two small basic proteins that are not made when homologous DNA containing a deletion that overlaps both the su3⁺ gene and the gene for the putative protamine-like protein is used. DNA from phage that have regained the parental su3⁺ phenotype again direct in vitro synthesis of the basic proteins. Synthesis of basic protein is inhibited by the presence of ppGpp, as would be expected if the mRNA is part of a large RNA transcript that starts at the promoter for the tRNA₁ ^Tyr gene.