title: Uncoupling of actin-activated myosin ATPase activity from actin binding by a monoclonal antibody directed against the N-terminus of myosin light chain 1.
abstract: The role of the N-terminal region of myosin light chain 1 (LC1) in actomyosin interaction was investigated using an IgG monoclonal antibody (2H2) directed against the N-terminal region of LC1. We defined the binding site of 2H2 by examining its cross-reactivity with myosin light chains from a variety of species and with synthetic oligopeptides. Our findings suggest that 2H2 is directed against the N-terminal region of LC1 which includes the trimethylated alanine residue at the N-terminus. In the presence of 2H2, the rate of actomyosin superprecipitation was reduced, although the extent was not. 2H2 caused a reduction in the Vmax of both myosin and chymotryptic S1(A1) actin-activated ATPase activity, while the Km appeared to be unaltered. The Mg(2+)-ATPase activity of myosin alone was also unaffected. Binding studies revealed that 2H2 did not prevent the formation of acto-S1 complex, either in the presence or in the absence of ATP, nor did it affect the ability of ATP to dissociate S1 from F-actin. Our findings suggest that the N-terminal region of LC1 is not essential for actin binding but is involved in modulating actin-activated ATPase activity of myosin.
authors.affiliation: Department of Anatomy, University of Sydney, NSW, Australia.
authors.forename: W
authors.initials: W
authors.lastname: Boey
authors.forename: A W
authors.initials: AW
authors.lastname: Everett
authors.forename: J
authors.initials: J
authors.lastname: Sleep
authors.forename: J
authors.initials: J
authors.lastname: Kendrick-Jones
authors.forename: C G
authors.initials: CG
authors.lastname: dos Remedios
mesh_terms: D000199:Actins / Q000378:metabolism* / Q000494:pharmacology*; D000205:Actomyosin / Q000378:metabolism; D000818:Animals; D000911:Antibodies, Monoclonal; D001666:Binding Sites, Antibody; D015153:Blotting, Western; D011232:Chemical Precipitation; D004789:Enzyme Activation / Q000187:drug effects; D004797:Enzyme-Linked Immunosorbent Assay; D007074:Immunoglobulin G; D015879:Myosin Subfragments / Q000276:immunology / Q000378:metabolism; D009218:Myosins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D010446:Peptide Fragments / Q000276:immunology / Q000378:metabolism; D011817:Rabbits; D012689:Sequence Homology, Nucleic Acid
chemical_list: D000199:Actins; D000911:Antibodies, Monoclonal; D007074:Immunoglobulin G; D015879:Myosin Subfragments; D010446:Peptide Fragments; D000205:Actomyosin; D009218:Myosins