Figure 1.

Catalytic domain of the serine/threonine and tyrosine protein kinases (adapted from Rudrabhatla et al.¹⁹). The catalytic kinase domain of around 250 amino acids contains 11 conserved subdomains (I to XI). At the N-terminal extremity, the subdomain II has a conserved lysine residue believed to be involved in ATP binding. In the central part, an aspartic acid residue in subdomain VII is important for the catalytic activity of the kinase. Subdomains VI and VIII are specifically conserved in either serine/threonine or tyrosine kinases. Consensus DL(R/A)A(A/R)N is specific of tyrosine kinases whereas the consensus DLKXXN is serine/threonine-specific. Subdomain VIII has a tyrosine-specific consensus XP(I/V)(K/R)W(T/M)APE and a poorly conserved serine/threonine-specific consensus G(T/S)XX(Y/F)XAPE. In subdomain XI, the consensus CW(X)₆RPXF in subdomain XI is tyrosine-specific.