Beta-adrenergic receptor kinase. Agonist-dependent receptor binding promotes kinase activation.

摘要: The beta-adrenergic receptor kinase (beta ARK) specifically phosphorylates the activated form of multiple receptors such as beta 2-adrenergic 2 AR) and rhodopsin. ARK also synthetic peptides, albeit with an approximately 10(4)-10(7)-fold lower Vmax/Km ratio compared to receptors, a clear preference for peptides containing acidic residues on aminoterminal side serine or threonine. To further characterize mechanism substrate phosphorylation by ARK, we designed series analogue single amino acid change (serine, glutamic acid, phosphoserine) situated 4 amino-terminal target serine. While weakly phosphorylated lacking residue, either phosphoserine were substantially better substrates 3.5- 8-fold increase in Vmax. Additional studies demonstrated that interaction 2AR* Rho*) significantly enhanced peptide phosphorylation. Both Rho* truncated rhodopsin its carboxyl-terminal sites similar extent EC50 values activation 0.65 1.34 microM, respectively. In contrast, agonist-occupied 2AR higher affinity (EC50 0.012 microM) Rho*. poor RRRASAAASAA was increased up 200-fold while good (RRREEEEESAAA) only 8-fold. Our results suggest (glutamic localized serines are important but not essential determinants directing specificity appears rely more strongly overall topological structure which promotes specific binding ARK.