Role of the N-terminal region of the regulatory light chain in the dephosphorylation of myosin by myosin light chain phosphatase

UMMS Affiliation

Department of Physiology

Publication Date


Document Type



Amino Acid Sequence; Animals; Molecular Sequence Data; Myosin Light Chains; Myosin-Light-Chain Phosphatase; Phosphoprotein Phosphatases; Phosphorylation; Protein Kinase C; Substrate Specificity; Turkeys


Life Sciences | Medicine and Health Sciences


Myosin regulatory light chain (RLC) is phosphorylated at various sites at its N-terminal region, and heterotrimeric myosin light chain phosphatase (MLCP) has been assigned as a physiological phosphatase that dephosphorylates myosin in vivo. Specificity of MLCP toward the various phosphorylation sites of RLC was studied, as well as the role of the N-terminal region of RLC in the dephosphorylation of myosin by MLCP. MLCP dephosphorylated phosphoserine 19, phosphothreonine 18, and phosphothreonine 9 efficiently with almost identical rates, whereas it failed to dephosphorylate phosphorylated serine 1/serine 2. Deletion of the N-terminal seven amino acid residues of RLC markedly decreased the dephosphorylation rate of phosphoserine 19 of RLC incorporated in the myosin molecule, whereas this deletion did not significantly affect the dephosphorylation rate of isolated RLC. On the other hand, deletion of only four N-terminal amino acid residues showed no effect on dephosphorylation of phosphoserine 19 of incorporated RLC. The inhibition of dephosphorylation by deletion of the seven N-terminal residues was also found with the catalytic subunit of MLCP. Phosphorylation at serine 1/serine 2 and threonine 9 did not influence the dephosphorylation rate of serine 19 and threonine 18 by MLCP. These results suggest that the N-terminal region of RLC plays an important role in substrate recognition of MLCP.

DOI of Published Version



J Biol Chem. 1999 Oct 15;274(42):30122-6.

Journal/Book/Conference Title

The Journal of biological chemistry

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Link to Article in PubMed

PubMed ID