[Gene 26 of bacteriophage T4 baseplate. II. Synthesis of a smaller peptide of gene 26 is initiated at an unusual AUU-codon].

The sequence of gene 26 consisting of 624 nucleotides codes for two peptides whereby the smaller peptide (gp26*) is encoded by the 3'-end of the same open reading frame. Expression of gene 26 from plasmids, containing various fragments from the terminal part of this gene, allowed us to determine the gene 26 internal segment responsible for the initiation of gp26* synthesis. By site-directed mutagenesis the nucleotide sequence of this DNA segment has been changed, and in further expression experiments of the mutagenized gene 26 it was determined that an unusual AUU codon, triplet 114 of gene 26, is used to initiate the synthesis of the smaller peptide. Thus gene 26 encodes two peptides of M(r) 23,880 and M(r) 10,873. The regulation of the expression of gene 26 in T4-infected cells is discussed.