Role of basic residues in the phosphorylation of synthetic peptides by myosin light chain kinase

B. E. Kemp, R. B. Pearson, C. House

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The substrate specificity of the chicken gizzard myosin light chain kinase has been studied by using a series of synthetic peptide analogs of the NH2-terminal sequence of the chicken gizzard myosin light chain (M(r) = 20,000). An 18-residue synthetic peptide, Arg-Pro-Gln-Arg-Ala-Lys-Ala-Lys-Thr-Thr-Lys-Ala-Thr-Ser(19)-Asn-Val-Phe-Se r-NH2, corresponding to the sequence reported by Maita et al. [Maita, T., Chen, J.I. & Matsuda, G. (1981) Eur.J.Biochem. 117, 417-424], was phosphorylated with a 22-fold higher K(m) and a V(max) that was decreased to 1% of the native protein substrate. This peptide was also an inferior substrate when compared with an 18-residue synthetic peptide with an alternative sequence, Lys-Ala-Lys-Thr-Thr-Lys(11)-Lys(12)-Arg(13)-Pro-Gln-Arg-Ala-Thr-Ser(19)-As n-Val-Phe-Ser-NH2, which was phosphorylated with an apparent K(m) of 6.9 μM, comparable to the native protein substrate of 8.6 μM, and a V(max) of 3.9 μ, 11% of that for the protein substrate. The kinetics of phosphorylation of shortened peptides corresponding to both sequences, together with peptides with appropriate substitution, indicated that basic residues were the primary determinants of specificity for the smooth muscle myosin light chain kinase. In the latter peptide sequence, lysin residues 11 and 12 and the arginine at position 13 had a major influence on the kinetics of peptide phosphorylation.

Original languageEnglish
Pages (from-to)7471-7475
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number24 I
Publication statusPublished - 1 Jan 1983
Externally publishedYes

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