Regulation of fission yeast myosin-II function and contractile ring dynamics by regulatory light-chain and heavy-chain phosphorylation.
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.
Sladewski
Thomas E
TE
Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, VT 05405, USA.
Previs
Michael J
MJ
Lord
Matthew
M
D000199:Actins / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D048749:Cytokinesis / Q000502:physiology*; D003599:Cytoskeleton / Q000378:metabolism; D008969:Molecular Sequence Data; D018995:Myosin Heavy Chains / Q000235:genetics / Q000378:metabolism*; D024462:Myosin Type II / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012568:Schizosaccharomyces / Q000166:cytology / Q000502:physiology; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism*
D000199:Actins; C434211:MYO2 protein, S pombe; D011993:Recombinant Fusion Proteins; D029702:Schizosaccharomyces pombe Proteins; C490463:rlc1 protein, S pombe; D000251:Adenosine Triphosphatases; D024462:Myosin Type II; D018995:Myosin Heavy Chains