Abstract
Gene 28 of B. subtilis bacteriophage SPO1 codes for a regulatory protein, a .sigma. factor known as .sigma.gp28, that binds to the bacterial core RNA polymerase to direct the recognition of phage middle gene promoters, middle promoters exhibit distinctive and conserved nucleotide sequences in 2 regions centered .apprx. 10 and 35 base pairs upstream from the start point of mRNA synthesis. The cloning of gene 28 and its complete nucleotide sequence are reported. .sigma.gp28 is a 25,707-dalton protein of 220 amino acids. Neither the nucleotide sequence of gene 28 nor the inferred amino acid sequence of .sigma.gp28 exhibits extensive homology to the gene or protein sequence of Escherichia coli .sigma. factor.