title: Effect of lysine methylation and other ATPase modulators on the active site of myosin subfragment 1.
abstract: Many and diverse modifications of the myosin subfragment 1 (S-1) increase (modulate) its ATPase activity, including interaction of this particle with actin; a recent addition to these modifications is the extensive lysine modification of S-1 that seems prerequisite to crystallizing it for structure analysis. In this study we first established kinetically the ATPase modulations induced by various treatments of the myosin S-1 enzyme, and we also measured two properties of the S-1 active site--the affinity with which the site binds (a fluorescent analog of) the enzymatic nucleotide product and the access that a fluorescence quencher has to the bound ADP product--in an effort to get at the mechanism of modulation. Modulations achieved by substituting Ca2+ for the normal Mg2+ cocatalyst or by substituting Cl- for the normal carboxylate anion seem due to the product being held more loosely by the modulated enzyme. In other illustrative modulations (lysine methylation, or alkylation of Cys-707, or transition from neutral pH to pH 9.2) nucleotide product affinity and access to quencher do change, but not in a pattern explained simply by a lifting of product inhibition. Lysine methylation results in weaker binding of nucleotide product.
authors.affiliation: Physiology Department, University of the Pacific, San Francisco, CA 94115.
authors.forename: D B
authors.initials: DB
authors.lastname: Bivin
authors.forename: K
authors.initials: K
authors.lastname: Ue
authors.forename: M
authors.initials: M
authors.lastname: Khoroshev
authors.forename: M
authors.initials: M
authors.lastname: Morales
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D001665:Binding Sites; D002412:Cations; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008239:Lysine / Q000378:metabolism*; D008745:Methylation; D015879:Myosin Subfragments / Q000378:metabolism*; D009218:Myosins / Q000378:metabolism*; D009994:Osmolar Concentration; D013329:Structure-Activity Relationship
chemical_list: D002412:Cations; D015879:Myosin Subfragments; D000244:Adenosine Diphosphate; D009218:Myosins; D008239:Lysine