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Effects of mutations in the gamma-phosphate binding site of myosin on its motor function
UMass Chan Affiliations
Department of PhysiologyDocument Type
Journal ArticlePublication Date
1998-10-09Keywords
ActinsAdenosine Diphosphate
Adenosine Triphosphate
Binding Sites
Catalytic Domain
Flow Injection Analysis
Hydrolysis
Models, Chemical
Models, Molecular
*Motion
Muscle, Smooth
Mutation
Myosins
Protein Binding
Recombinant Proteins
Life Sciences
Medicine and Health Sciences
Metadata
Show full item recordAbstract
The role of the highly conserved residues in the gamma-phosphate binding site of myosin upon myosin motor function was studied. Each of five residues (Ser181, Lys185, Asn235, Ser236, and Arg238) in smooth muscle myosin was mutated. K185Q has neither a steady state ATPase nor an initial Pi burst. Although ATP and actin bind to K185Q, it is not dissociated from actin by ATP. These results indicate that the hydrolysis of bound ATP by K185Q is inhibited. S236T has nearly normal basal Mg2+-ATPase activity, initial Pi burst, ATP-induced enhancement of intrinsic tryptophan fluorescence, and ATP-induced dissociation from actin. However, the actin activation of the Mg2+-ATPase activity and actin translocation of S236T were blocked. In contrast S236A has nearly normal enzymatic properties and actin-translocating activity. These results indicate that 1) the hydroxyl group of Ser236 is not critical as an intermediary of proton transfer during the ATP hydrolysis step, and 2) the bulk of the extra methyl group of the threonine residue in S236T blocks the acceleration of product release from the active site by actin. Arg238, which interacts with Glu459 at the Switch II region, was mutated to Lys and Ile, respectively. R238K has essentially normal enzymatic activity and motility. In contrast, R238I does not hydrolyze ATP or support motility, although it still binds ATP. These results indicate that the charge interaction between Glu459 and Arg238 is critical for ATP hydrolysis by myosin. Other mutants, S181A, S181T, and N235I, showed nearly normal enzymatic and motile activity.Source
J Biol Chem. 1998 Oct 16;273(42):27404-11.
DOI
10.1074/jbc.273.42.27404Permanent Link to this Item
http://hdl.handle.net/20.500.14038/42423PubMed ID
9765269Related Resources
ae974a485f413a2113503eed53cd6c53
10.1074/jbc.273.42.27404