Smooth muscle myosin kinase requires residues on the COOH-terminal side of the phosphorylation site. Peptide inhibitors

Abstract

The COOH-terminal residue in peptide analogs of the phosphorylation site sequence in smooth muscle myosin light chains, Lys11-Lys12-Arg13-Ala-Ala-Arg16-Ala-Thr-Ser19-(P)Asn20- Val21-Phe22-Ala23, were shown to have a strong influence on the kinetics of peptide phosphorylation. The peptides 11-19, 11-20, 11-21, 11-22, 11-23 were all phosphorylated by the myosin light chain kinase with similar apparent K(m) values in the range 11-17 μM. The V(max) varied 40-fold, with the peptides 11-19, 11-20, 11-21, 11-22, and 11-23 having V(max) values of 0.035, 0.045, 0.32, 1.74, and 1.43 μmol.min-1.mg-1 respectively. These results indicated that Ala23 was not essential whereas Phe22 and Val21 had a strong ..