Bacillus subtilis sucrose-specific enzyme II of the phosphotransferase system: expression in Escherichia coli and homology to enzymes II from enteric bacteria

Abstract

Sucrose is transported into Bacillus subtilis cells by way of a phosphotransferase system, which consists of a specific enzyme II, a nonspecific enzyme I, and a histidine-containing phosphocarrier protein. Mutations in the sacP locus abolish the specific transport of sucrose. The B. subtilis sacP gene was cloned and expressed in Escherichia coli, and transformed cells could transport and phosphorylate sucrose. This indicates that the sacP gene product is enzyme II of the sucrose phosphotransferase system of B. subtilis. The nucleotide sequence of the sacP gene was determined and was found to overlap with the sacA gene at the tetranucleotide ATGA, which may allow a translational coupling between sacP and sacA. The two genes are therefore probably organized in an operon structure with the promoter located 5' to sacP gene. The deduced amino acid sequence gave a Mr of 48,945 for the sucrose-specific enzyme II polypeptide. The amino acid sequence was compared to that of three other known enteric bacterial enzymes II (beta-glucoside-specific enzyme II, mannitol-specific enzyme II, and glucose-specific enzyme II). Homology was found with beta-glucoside enzyme II, and well conserved regions were identified through the comparison of the proteins.