Fig. 1. A simplified representation of the adenine-binding pocket showing the signature amino acid residues (Tyr94 is not shown). The first three residues belong to the glycine loop (residues 17–38). They form the “ceiling” of the adenine-binding pocket. The hinge sequence consists of residues 92–96 (Met92 is the gatekeeper), but residues 93 and 96 contribute to ligand binding only with their backbone atoms, therefore, they were excluded from consideration

Fig. 2. Groups of STPKs of gram-positive bacteria (Zakharevich et al., [19])

Fig. 3. This Venn diagram represents distribution of groups of serine/threonine protein kinases into three clusters. Roman numerals represent kinase groups according to our classification (Zakharevich et al., [19]). Groups XIV, XV, XVII, and XX are not included because: 1) the microorganisms belonging to these groups are neither pathogens nor symbionts of the human microbiota and 2) no similarities were detected between STPK signatures of these 4 groups and signatures of human protein kinases