Myosin heavy-chain kinase A (MHCK A) catalyses the disassembly of myosin II filaments in Dictyostelium cells via myosin II heavy-chain phosphorylation. MHCK A possesses a ‘coiled-coil’-enriched domain that mediates the oligomerization, cellular localization and actin-binding activities of the kinase. F-actin (filamentous actin) binding by the coiled-coil domain leads to a 40-fold increase in MHCK A activity. In the present study we examined the actin-binding characteristics of the coiled-coil domain as a means of identifying mechanisms by which MHCK A-mediated disassembly of myosin II filaments can be regulated in the cell. Co-sedimentation assays revealed that the coiled-coil domain of MHCK A binds co-operatively to F-actin with an apparent KD of approx. 0.5 μM and a stoichiometry of approx. 5:1 [actin/C(1–498)]. Further analyses indicate that the coiled-coil domain binds along the length of the actin filament and possesses at least two actin-binding regions. Quite surprisingly, we found that the coiled-coil domain cross-links actin filaments into bundles, indicating that MHCK A can affect the cytoskeleton in two important ways: (1) by driving myosin II-filament disassembly via myosin II heavy-chain phosphorylation, and (2) by cross-linking/bundling actin filaments. This discovery, along with other supporting data, suggests a model in which MHCK A-mediated bundling of actin filaments plays a central role in the recruitment and activation of the kinase at specific sites in the cell. Ultimately this provides a means for achieving the robust and highly localized disruption of myosin II filaments that facilitates polarized changes in cell shape during processes such as chemotaxis, cytokinesis and multicellular development.
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Research Article|
March 28 2006
Myosin heavy-chain kinase A from Dictyostelium possesses a novel actin-binding domain that cross-links actin filaments
Misty Russ;
Misty Russ
1
1Department of Biology, University of North Carolina at Greensboro, Greensboro, NC 27402, U.S.A.
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Daniel Croft;
Daniel Croft
1
1Department of Biology, University of North Carolina at Greensboro, Greensboro, NC 27402, U.S.A.
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Omar Ali;
Omar Ali
1Department of Biology, University of North Carolina at Greensboro, Greensboro, NC 27402, U.S.A.
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Raquel Martinez;
Raquel Martinez
1Department of Biology, University of North Carolina at Greensboro, Greensboro, NC 27402, U.S.A.
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Paul A. Steimle
Paul A. Steimle
2
1Department of Biology, University of North Carolina at Greensboro, Greensboro, NC 27402, U.S.A.
2To whom correspondence should be addressed (email p_steiml@uncg.edu).
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Publisher: Portland Press Ltd
Received:
August 22 2005
Revision Received:
December 20 2005
Accepted:
December 22 2005
Accepted Manuscript online:
December 22 2005
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London
2006
Biochem J (2006) 395 (2): 373–383.
Article history
Received:
August 22 2005
Revision Received:
December 20 2005
Accepted:
December 22 2005
Accepted Manuscript online:
December 22 2005
Citation
Misty Russ, Daniel Croft, Omar Ali, Raquel Martinez, Paul A. Steimle; Myosin heavy-chain kinase A from Dictyostelium possesses a novel actin-binding domain that cross-links actin filaments. Biochem J 15 April 2006; 395 (2): 373–383. doi: https://doi.org/10.1042/BJ20051376
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