An additional GerE-controlled gene encoding an abundant spore coat protein from Bacillus subtilis

We describe the identification and characterization of a gene, herein designated cotG, encoding an abundant coat protein from the spores of Bacillus subtilis. The cotG open reading frame is 195 codons in length and is capable of encoding a polypeptide of 24 kDa that contains nine tandem copies of the 13-amino-acid long, approximately repeated sequence H/Y-K-K-S-Y-R/C-S/T-H/Y-K-K-S-R-S. cotG is located at 300 degrees on the genetic map close to another coat protein gene, cotB. The cotG and cotB genes are in divergent orientation and are separated by 1.3 kb. Like the promoter for cotB, the cotG promoter is induced at a late stage of sporulation under the control of the RNA polymerase sigma factor sigma K and the DNA-binding protein GerE. The -10 and -35 nucleotide sequences of the cotG promoter resemble those of other promoters recognized by sigma K-containing RNA polymerase, and centered 70 bp upstream of the apparent start site is a sequence that matches the consensus binding site for GerE. Spore coat proteins from a newly constructed cotG null mutant lack not only CotG but also CotB, a finding that suggests that CotG may be a morphogenetic protein that is required for the incorporation of CotB into the coat.