Figure 1.

Domain structure of BY kinases. A periplasmic (gram-negatives) or extracellular (gram-positives) sensory loop is linked to the catalytic intracellular domain, either contiguously (gram-negatives) or through protein–protein interaction (gram-negatives). The catalytic domain contains Walker A, B and A′ motifs (blue). A tyrosine-rich region (red) containing the phosphorylation sites is present in the C-terminus, and gram-negative BY kinases also possess an internal tyrosine (red) that can be autophosphorylated. Walker motifs A, A′ and B can be identified by conserved sequences motifs. BY, bacterial tyrosine.