Amino acid sequence around a "hinge" region and its "autophosphorylation" site in bovine Lung cGMP-dependent protein kinase.

An exposed "hinge" region of cGMP-dependent protein kinase is known to be susceptible to both limited proteolysis and autophosphorylation. A 91-residue fragment has been isolated from this region and its amino acid sequence has been compared with the analogous regions of the cAMP-dependent protein kinases. Although a resemblance among these sequences is not striking, the phosphorylation sites are in corresponding regions toward the NH2 termini, and there are indications of homology in the vicinity of their autophosphorylation sites. As in the cAMP-dependent protein kinase, the site of autophosphorylation and the site of susceptibility to limited proteolysis are very near each other in the primary structure. The actual site of autophosphorylation (the underlined threonine residue in Pro-Arg-Thr-Thr-Arg) is quite different from those in the regulatory subunit of Type II cAMP-dependent kinase or the site in Type I regulatory subunit that can be phosphorylated by the cGMP-dependent protein kinase.