Phosphorylation of a single head of smooth muscle myosin activates the whole molecule.

Biochemistry
Arthur S RovnerK M Trybus

Abstract

Regulatory light chain (RLC) phosphorylation activates smooth and non-muscle myosin II, but it has not been established if phosphorylation of one head turns on the whole molecule. Baculovirus expression and affinity chromatography were used to isolate heavy meromyosin (HMM) containing one phosphorylated and one dephosphorylated RLC (1-P HMM). Motility and steady-state ATPase assays indicated that 1-P HMM is nearly as active as HMM with two phosphorylated heads (2-P HMM). Single-turnover experiments further showed that both the dephosphorylated and phosphorylated heads of 1-P HMM can be activated by actin. Singly phosphorylated full-length myosin was also an active species with two cycling heads. Our results suggest that phosphorylation of one RLC abolishes the asymmetric inhibited state formed by dephosphorylated myosin [Liu, J., et al. (2003) J. Mol. Biol. 329, 963-972], allowing activation of both the phosphorylated and dephosphorylated heads. These findings help explain how smooth muscles are able to generate high levels of stress with low phosphorylation levels.

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Citations

Apr 21, 2010·Proceedings of the National Academy of Sciences of the United States of America·David KastDavid D Thomas
May 8, 2009·The Journal of Biological Chemistry·Sam WalcottDavid M Warshaw
Oct 27, 2010·The Journal of Biological Chemistry·Hailong LuKathleen M Trybus
Jun 22, 2012·The Journal of Biological Chemistry·Hailong LuMichael R Diehl
Apr 15, 2008·The Journal of Biological Chemistry·Hiroto TanakaMitsuo Ikebe
Nov 15, 2011·Journal of Molecular Biology·Bruce A J BaumannKenneth A Taylor
May 4, 2007·American Journal of Physiology. Cell Physiology·Thomas J Eddinger, Daniel P Meer
Jul 19, 2017·Biophysics Reviews·Darshan V TrivediJames A Spudich

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