Study of the phosphorylatable light chains of skeletal and gizzard myosins by nuclear magnetic resonance spectroscopy

Levine, Barry A.; Griffiths, Hugh; Patchell, Valerie B.; Perry, S. V.

doi:10.1042/bj2540277

Cited by 13 publications

(4 citation statements)

References 31 publications

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“…35 If these N-terminal residues occupied a fixed position on the myosin lever arm in the dephosphorylated state they could affect the modelling results, depending on their actual structure and interactions. However, such a fixed interaction has not been demonstrated.…”

Section: Validation Of the Modelsmentioning

confidence: 99%

The Requirement for Mechanical Coupling Between Head and S2 Domains in Smooth Muscle Myosin ATPase Regulation and its Implications for Dimeric Motor Function

Tama

Feig

et al. 2005

Journal of Molecular Biology

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Section: Validation Of the Modelsmentioning

confidence: 99%

The Requirement for Mechanical Coupling Between Head and S2 Domains in Smooth Muscle Myosin ATPase Regulation and its Implications for Dimeric Motor Function

Tama

Feig

et al. 2005

Journal of Molecular Biology

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“…The site of phosphorylation is a serine residue, 19 amino acids from the N-terminus. This region of the RLC is highly mobile (7). Mutagenesis studies suggest that a phosphate in this position has two distinct functions: ( 1 ) controlling monomer to filament transitions; and ( 2 ) turning on the actin-activated adenosine triphosphatase (ATPase) activity.…”

Section: The Regulatory Mechanismmentioning

confidence: 99%

Regulation and Tuning of Smooth Muscle Myosin

Sweeney

1998

Am J Respir Crit Care Med

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Smooth muscle myosin is regulated by phosphorylation of one of the two myosin light chains. This phosphorylation causes an unfolding of the myosin that allows it to interact with actin to produce force. The inactive state involves trapping the myosin in a conformation wherein the myosin heads interact with a segment of the myosin rod. Phosphorylation of the regulatory light chain weakens these interactions and allows the myosin to be activated. Smooth muscle myosin has a large movement of its light chain binding domain that is coupled to ADP release. This structural change may be necessary for the generation of "latch." Smooth muscle myosin has three different regions that vary to generate different isoforms: (1) an alternative insertion within the myosin head; (2) two possible essential light chains; and (3) an alternative tail at the end of the myosin rod. There is substantial evidence that the insertion in the myosin head increases the enzymatic activity of the myosin and leads to greater shortening velocity. The function of the other two variants is as yet unclear.

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“…This hypothetical regulatory scheme also is supported by NMR results. The study of Levine et al (22) suggests that the N-terminal region of both rabbit skRLC and gizzard smRLC exhibits segmental mobility independent of the rest of the molecule. When the RLC is phosphorylated, mobility of the N-terminal segment is diminished and the serine phosphate is influenced by neighboring positively charged side chains.…”

Section: Regulation Via Phosphorylation Of the Myosins Containing Wilmentioning

confidence: 99%

Restoration of Phosphorylation-dependent Regulation to the Skeletal Muscle Myosin Regulatory Light Chain

Yang

Sweeney

1995

Journal of Biological Chemistry

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Regulation of the ATPase activity of smooth and nonmuscle myosin II involves reversible phosphorylation of the regulatory light chain (RLC). The RLC from skeletal muscle myosin (skRLC) is unable to confer regulation (myosin is locked in an inactive state) to smooth muscle myosin when substituted for the endogenous smooth RLC (smRLC). Studies of chimeric light chains comprised of the N-or C-terminal half of each skRLC and smRLC suggest that the structural basis for the loss of this regulation is within the C-terminal half of the RLC (Trybus, K. M., and Chatman, T. A. (1993) J. Biol. Chem. 268, 4412-4419). The purpose of this study is to delineate the structural elements within the C-terminal half of the smRLC that are absent in the skRLC and are necessary for regulation. By sequence comparison, six residues, Arg-103, Arg-123, Met-129, Gly-130, Arg-143, and Arg-160, which are conserved in regulated myosin RLCs but missing in nonregulated myosin RLCs, were identified in smRLC. To test whether these amino acids provide the missing structural elements necessary for phosphorylation-mediated regulation, a skRLC was engineered that replaced the corresponding skRLC amino acids (positions 100, 120, 126, 127, 140, and 157, respectively) with their smRLC counterparts. Using a newly developed RLC exchange procedure, the purified mutant protein was evaluated for its ability to regulate chicken gizzard smooth muscle myosin. Substitution of the six conserved amino acids into the skRLC completely restored phosphorylation-mediated regulation. Thus, a subset of these amino acids, including four basic arginine residues located in the E, F, G, and H helices which are missing in skRLC, may be the structural coordinates for the phosphorylserine in the N terminus. Based on this result, the regulation of glycogen phosphorylase is discussed as a model for the regulation of smooth muscle myosin.Unlike striated muscle, the initiation of smooth muscle contraction must be preceded by serine phosphorylation of the myosin RLC 1 which is accomplished by a calcium/calmodulindependent myosin light chain kinase in the presence of ATP (1). Although the RLC is also reversibly phosphorylated in vertebrate striated muscle (at a homologous serine), this phosphorylation simply modulates contractile activity (2). The loss of myosin regulation in striated muscle is due to undetermined alterations in the myosin heavy chain. Additionally, the smooth muscle and skeletal muscle RLCs are not functionally equivalent, even though the RLCs from skeletal muscle and smooth muscle are highly homologous (71% similarity and 53% identity in sequence). The RLC from skeletal muscle myosin (skRLC) is unable to confer regulation to smooth muscle myosin (a phosphorylation-regulated myosin) and locks the myosin in the "off" state when substituted for the endogenous smooth muscle RLC (smRLC) (3). Additionally, the smRLC can confer calcium sensitivity to scallop muscle myosin (a Ca 2ϩ -regulated myosin), while the skRLC fails to do so (4). However, no RLC can inhibit the activ...

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Study of the phosphorylatable light chains of skeletal and gizzard myosins by nuclear magnetic resonance spectroscopy

Cited by 13 publications

References 31 publications

The Requirement for Mechanical Coupling Between Head and S2 Domains in Smooth Muscle Myosin ATPase Regulation and its Implications for Dimeric Motor Function

The Requirement for Mechanical Coupling Between Head and S2 Domains in Smooth Muscle Myosin ATPase Regulation and its Implications for Dimeric Motor Function

Regulation and Tuning of Smooth Muscle Myosin

Restoration of Phosphorylation-dependent Regulation to the Skeletal Muscle Myosin Regulatory Light Chain

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