FIG 1.

In silico analysis of sporulation-associated histidine kinases. (A) Tan boxes represent predicted transmembrane domains; the H⁺ ATPase region includes the kinase catalytic domain (56, 57). DHpt, dimerization and histidine phosphotransferase; aa, amino acids. (B) Alignment of the dimerization and histidine phosphotransfer subdomains of C. difficile, B. subtilis, and B. anthracis sporulation kinases and E. coli EnvZ. The known or suspected conserved histidine is underlined. Asterisks represent the residues involved in direct interactions with the cognate response regulators (11, 61, 62), and shaded residues are highly conserved in C. difficile. E.c., E. coli; B.s., B. subtilis; B.a., Bacillus anthracis.