Chicken smooth muscle myosin light chain kinase is acetylated on its NH2-terminal methionine

  • Maree C. Faux
  • Kenneth I. Mitchelhill
  • Frosa Katsis
  • Richard E. H. Wettenhall
  • Bruce E. Kemp
Part of the Developments in Molecular and Cellular Biochemistry book series (DMCB, volume 11)


The reported cDNA structure of chicken smooth muscle myosin light chain kinase (smMLCK) encodes a protein of 972 residues (Olson et al. Proc. Natl. Acad. Sci USA, 87: 2284–2288, 1990). The calculated Mr is 107,534 whereas the estimate by SDS-PAGE is approximately 130,000. Gibson and Higgins (DNA Sequence (in press)) have recently reported the possibility of errors in the cDNA sequence for non-muscle MLCK and that the NH2-terminus of both it and smMLCK may extend beyond the reported coding region. The native smMLCK is NH2-terminally blocked. A CNBr peptide derived from smMLCK contains the NH2-terminal sequence Asp-Phe-Arg-Ala corresponding to residues 2 to 4 in the smMLCK sequence indicating that Met-1 is present. Using a limited thermolysin digest we isolated an NH2-terminally blocked peptide by reversed-phase HPLC. This thermolytic peptide had a mass of approximately 797 by time of flight mass spectrometry. Amino acid analysis and Edman sequencing of a CNBr-subfragment of the thermolytic peptide indicated that it had the composition and sequence, (Met)-Asp-Phe-Arg-Ala-Asn, with a calculated mass of 753. The difference in mass corresponds to the NH2-terminal Met being blocked by acetylation. The results demonstrate that the NH2-terminal sequence of smMLCK inferred from the reported cDNA sequence is correct and that the proposed initiating Met is not removed, but modified by α-NH2 acetylation of the translation product. (Mol Cell Biochem 127/128: 81–91, 1993)

Key words

myosin light chain kinase smooth muscle 


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Copyright information

© Kluwer Academic Publishers 1993

Authors and Affiliations

  • Maree C. Faux
    • 1
  • Kenneth I. Mitchelhill
    • 1
  • Frosa Katsis
    • 1
  • Richard E. H. Wettenhall
    • 2
  • Bruce E. Kemp
    • 1
  1. 1.St Vincent’s Institute of Medical ResearchFitzroyAustralia
  2. 2.Department of BiochemistryThe University of MelbourneParkvilleAustralia

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