Myosin light chain phosphorylation affects the structure of rabbit skeletal muscle thick filaments

Rhea J C Levine, Robert W. Kensler, Zhaohui Yang, James T. Stull, H. Lee Sweeney

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Abstract

To identify the structural basis for the observed physiological effects of myosin regulatory light chain phosphorylation in skinned rabbit skeletal muscle fibers (potentiation of force development at low calcium), thick filaments separated from the muscle in the relaxed state, with unphosphorylated light chains, were incubated with specific, intact, myosin light chain kinase at moderate (pCa 5.0) and low (pCa 5.8) calcium and with calcium-independent enzyme in the absence of calcium, then examined as negatively stained preparations, by electron microscopy and optical diffraction. All such experimental filaments became disordered (lost the near-helical array of surface myosin heads typical of the relaxed state). Filaments incubated in control media, including intact enzyme in the absence of calcium, moderate calcium (pCa 5.0) without enzyme, and bovine serum albumin substituting for calcium-independent myosin light chain kinase, all retained their relaxed structure. Finally, filaments disordered by phosphorylation regained their relaxed structure after incubation with a protein phosphatase catalytic subunit. We suggest that the observed disorder is due to phosphorylation-induced increased mobility and/or changed conformation of myosin heads, which places an increased population of them close to thin filaments, thereby potentiating actin-myosin interaction at low calcium levels.

Original languageEnglish (US)
Pages (from-to)898-907
Number of pages10
JournalBiophysical Journal
Volume71
Issue number2
StatePublished - Aug 1996

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Myosin Light Chains
Skeletal Muscle
Phosphorylation
Rabbits
Calcium
Myosins
Myosin-Light-Chain Kinase
Enzymes
Phosphoprotein Phosphatases
Skeletal Muscle Fibers
Bovine Serum Albumin
Transmission Electron Microscopy
Actins
Catalytic Domain
Light
Muscles

ASJC Scopus subject areas

  • Biophysics

Cite this

Levine, R. J. C., Kensler, R. W., Yang, Z., Stull, J. T., & Sweeney, H. L. (1996). Myosin light chain phosphorylation affects the structure of rabbit skeletal muscle thick filaments. Biophysical Journal, 71(2), 898-907.

Myosin light chain phosphorylation affects the structure of rabbit skeletal muscle thick filaments. / Levine, Rhea J C; Kensler, Robert W.; Yang, Zhaohui; Stull, James T.; Sweeney, H. Lee.

In: Biophysical Journal, Vol. 71, No. 2, 08.1996, p. 898-907.

Research output: Contribution to journalArticle

Levine, RJC, Kensler, RW, Yang, Z, Stull, JT & Sweeney, HL 1996, 'Myosin light chain phosphorylation affects the structure of rabbit skeletal muscle thick filaments', Biophysical Journal, vol. 71, no. 2, pp. 898-907.
Levine, Rhea J C ; Kensler, Robert W. ; Yang, Zhaohui ; Stull, James T. ; Sweeney, H. Lee. / Myosin light chain phosphorylation affects the structure of rabbit skeletal muscle thick filaments. In: Biophysical Journal. 1996 ; Vol. 71, No. 2. pp. 898-907.
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