J. Biol. Chem., Vol. 261, Issue 18, 8320-8326, Jun, 1986
Phosphorylation of synthetic peptides by skeletal muscle myosin light chain kinases
CH Michnoff, BE Kemp and JT Stull
Substrate determinants for rabbit and chicken skeletal muscle myosin light
chain kinases were examined with synthetic peptides. Both skeletal muscle
myosin light chain kinases had similar phosphorylation kinetics with
synthetic peptide substrates. Average kinetic constants for skeletal muscle
myosin light chain heptadecapeptide, (formula; see text) where S(P) is
phosphoserine, were Km, 2.3 microM and Vmax, 0.9 mumol/min/mg of enzyme. Km
values were 122 and 162 microM for skeletal muscle peptides containing A-A
for basic residues at positions 2-3 and 6-7, respectively. Average kinetic
constants for smooth muscle myosin light chain peptide, (formula; see
text), were Km, 1.4 microM and Vmax 27 mumol/min/mg of enzyme. Average Km
values for the smooth muscle peptide, residues 11-23, were 10 microM which
increased 6- and 11-fold with substitutions of alanine at residues 12 and
13, respectively. Vmax values decreased and Km values increased markedly by
substitution of residue 16 with glutamate in the 11-23 smooth muscle
tridecapeptide. Basic residues located 3 and 6-7 residues toward the NH2
terminus from phosphoserine in smooth muscle myosin light chain and 6-8 and
10-11 residues toward the NH2 terminus from phosphoserine in skeletal
muscle myosin light chain appear to be important substrate determinants for
skeletal muscle myosin light chain kinases. These properties are different
from myosin light chain kinase from smooth muscle.