NDLI: Smooth Muscle Heavy Meromyosin Phosphorylated on One of Its Two Heads Supports Force and Motion*

Content Provider	PubMed Central
Author	Walcott, Sam Fagnant, Patricia M. Trybus, Kathleen M. Warshaw, David M.
Abstract	Smooth muscle myosin is activated by regulatory light chain (RLC) phosphorylation. In the unphosphorylated state the activity of both heads is suppressed due to an asymmetric, intramolecular interaction between the heads. The properties of myosin with only one of its two RLCs phosphorylated, a state likely to be present both during the activation and the relaxation phase of smooth muscle, is less certain despite much investigation. Here we further characterize the mechanical properties of an expressed heavy meromyosin (HMM) construct with only one of its RLCs phosphorylated (HMM-1P). This construct was previously shown to have more than 50% of the ATPase activity of fully phosphorylated myosin (HMM-2P) and to move actin at the same speed in a motility assay as HMM-2P (Rovner, A. S., Fagnant, P. M., and Trybus, K. M. (2006) Biochemistry 45, 5280–5289). Here we show that the unitary step size and attachment time to actin of HMM-1P is indistinguishable from that of HMM-2P. Force-velocity measurements on small ensembles show that HMM-1P can generate approximately half the force of HMM-2P, which may relate to the observed duty ratio of HMM-1P being approximately half that of HMM-2P. Therefore, single-phosphorylated smooth muscle HMM molecules are active species, and the head associated with the unphosphorylated RLC is mechanically competent, allowing it to make a substantial contribution to both motion and force generation during smooth muscle contraction.
Related Links	http://dx.doi.org/10.1074/jbc.m109.003293
Ending Page	18251
Page Count	8
Starting Page	18244
File Format	PDF
ISSN	00219258
e-ISSN	1083351X
Journal	The Journal of Biological Chemistry
Issue Number	27
Volume Number	284
Language	English
Publisher	American Society for Biochemistry and Molecular Biology
Publisher Date	2009-07-03
Access Restriction	Open
Rights Holder	American Society for Biochemistry and Molecular Biology
Subject Keyword	Cell Biology Biochemistry Molecular Biology Research in Higher Education
Content Type	Text
Resource Type	Article
Subject	Cell Biology Biochemistry Molecular Biology

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Smooth Muscle Heavy Meromyosin Phosphorylated on One of Its Two Heads Supports Force and Motion

Smooth muscle heavy meromyosin phosphorylated on one of its two heads supports force and motion.

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Smooth Muscle Heavy Meromyosin Phosphorylated on One of Its Two Heads Supports Force and Motion*

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Smooth Muscle Heavy Meromyosin Phosphorylated on One of Its Two Heads Supports Force and Motion

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Smooth Muscle Heavy Meromyosin Phosphorylated on One of Its Two Heads Supports Force and Motion*