title: 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, and 11-23 were all phosphorylated by the myosin light chain kinase with similar apparent Km values in the range 11-17 microM. The Vmax varied 40-fold, with the peptides 11-19, 11-20, 11-21, 11-22, and 11-23 having Vmax values of 0.035, 0.045, 0.32, 1.74, and 1.43 mumol X min-1 X mg-1 respectively. These results indicated that Ala23 was not essential whereas Phe22 and Val21 had a strong influence on the Vmax of peptide phosphorylation. This series of peptides competitively inhibited myosin light chain phosphorylation with Ki values similar to their respective Km values. Peptide 11-19 had a Ki value of approximately 10 microM and a Vmax less than 0.1% of the value with myosin light chains and is therefore an effective inhibitor of the smooth muscle myosin kinase.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002236:Carbohydrate Conformation; D002645:Chickens; D005895:Gizzard, Avian / Q000201:enzymology; D007700:Kinetics; D009130:Muscle, Smooth / Q000201:enzymology*; D009218:Myosins / Q000378:metabolism*; D010455:Peptides / Q000494:pharmacology*; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors; D013329:Structure-Activity Relationship
chemical_list: D010455:Peptides; D047428:Protein Kinase Inhibitors; D009218:Myosins