CLONING, SEQUENCING, AND EXPRESSION OF BACTERIOPHAGE-BF23 LATE GENE-24 AND GENE-25 ENCODING TAIL PROTEINS

Two bacteriophage BF23 late genes, genes 24 and 25, were isolated on a 7.4-kb PstI fragment from the phage DNA, and their nucleotide sequenc es were determined. Gene 24 encodes a minor tail protein with the expe cted M(r) of 34,309, and gene 25 located 4 bp upstream of gene 24 enco des a major tail protein with the expected M(r) of 50,329. When total cellular RNA isolated from either phage-infected cells or cells bearin g the cloned genes was analyzed by the primer extension method using t he primers specific to either gene 25 or gene 24, we identified a poss ible late gene promoter, designated P25, in the 5'-flanking region of gene 25. This promoter was similar in structure to Escherichia coil pr omoters for sigma(70). Studies of the translational gene 25- and gene 24-lacZ fusions in the cloned gene system revealed that the promoter P 25 was responsible for the expression of both genes 25 and 24 even in the absence of the regulatory genes which were absolutely required for late gene expression in the normal phage-infected cells. These result s indicate that the two genes constitute an operon under the control o f P25 and that the regulatory gene products of BF23 do not participate directly in specifying the late gene promoter.