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Originally published as MBC in Press, 10.1091/mbc.E09-04-0346 on July 1, 2009

Vol. 20, Issue 17, 3941-3952, September 1, 2009

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Regulation of Fission Yeast Myosin-II Function and Contractile Ring Dynamics by Regulatory Light-Chain and Heavy-Chain Phosphorylation

Thomas E. Sladewski, Michael J. Previs, and Matthew Lord

Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, VT 05405

Submitted April 30, 2009; Revised June 17, 2009; Accepted June 23, 2009
Monitoring Editor: Rong Li

We investigated the role of regulatory light-chain (Rlc1p) and heavy-chain phosphorylation in controlling fission yeast myosin-II (Myo2p) motor activity and function during cytokinesis. Phosphorylation of Rlc1p leads to a fourfold increase in Myo2p's in vitro motility rate, which ensures effective contractile ring constriction and function. Surprisingly, unlike with smooth muscle and nonmuscle myosin-II, RLC phosphorylation does not influence the actin-activated ATPase activity of Myo2p. A truncated form of Rlc1p lacking its extended N-terminal regulatory region (including phosphorylation sites) supported maximal Myo2p in vitro motility rates and normal contractile ring function. Thus, the unphosphorylated N-terminal extension of Rlc1p can uncouple the ATPase and motility activities of Myo2p. We confirmed the identity of one out of two putative heavy-chain phosphorylation sites previously reported to control Myo2p function and cytokinesis. Although in vitro studies indicated that phosphorylation at Ser-1444 is not needed for Myo2p motor activity, phosphorylation at this site promotes the initiation of contractile ring constriction.

This was published online ahead of print in MBC in Press (http://www.molbiolcell.org/cgi/doi/10.1091/mbc.E09-04-0346) on July 1, 2009.

Address correspondence to: Matthew Lord (matthew.lord{at}uvm.edu)

Abbreviations used: ELC, essential light chain; FRAP, fluorescence recovery after photobleaching; LC-ESI-MS, liquid chromatography electrospray ionization-mass spectrometry; RLC, regulatory light chain; ROI, region of interest.




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V. C. Coffman, A. H. Nile, I-J. Lee, H. Liu, and J.-Q. Wu
Roles of Formin Nodes and Myosin Motor Activity in Mid1p-dependent Contractile-Ring Assembly during Fission Yeast Cytokinesis
Mol. Biol. Cell, December 15, 2009; 20(24): 5195 - 5210.
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