FIG. 2.
Classification of kinases by the sequence around the phosphorylated histidine. Kinases were sorted into classes on the basis of the sequence relationships of the residues on either side of the phosphorylated histidine. The classes were related to their response regulator based on the homology of the response regulator output domain to those of E. coli (19). Note the orphan kinases of group IIIB were related to NtrB of E. coli through the homology of the residues surrounding the histidine to NtrB, not through homologies to NtrC, a response regulator which does not exist in B. subtilis. Gaps introduced to maximize alignment are indicated by the dots.