title: The mechanism of inhibition of the actin-activated myosin MgATPase by calponin.
abstract: Calponin inhibits the actin-activated ATPase of smooth muscle myosin and thus has been proposed as a thin filament-based regulatory component in smooth muscle. To obtain information on the mechanism of inhibition by calponin we have used chemical modification of actin and cross-linking of actin and subfragment 1. Modification of Lys 61 of actin had no effect on the inhibition by calponin of acto-heavy meromyosin ATPase, i.e. different from tropomyosin-troponin. In addition, modification of the acidic N-terminal region of actin did not impair the ability of calponin to bind to F-actin. Finally, calponin was effective in inhibiting ATPase activity of cross-linked acto-subfragment 1. Therefore the mechanism of inhibition by calponin is distinct from troponin-tropomyosin and caldesmon in that it does not involve either the N-terminal acidic region of actin nor the area around Lys 61 and does not fit a simple steric blocking model.
authors.affiliation: Department of Applied Chemistry and BioTechnology, Fukui University, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Miki
authors.forename: M P
authors.initials: MP
authors.lastname: Walsh
authors.forename: D J
authors.initials: DJ
authors.lastname: Hartshorne
mesh_terms: D000199:Actins / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D001665:Binding Sites; D017301:Ca(2+) Mg(2+)-ATPase / Q000037:antagonists & inhibitors*; D002135:Calcium-Binding Proteins / Q000378:metabolism / Q000494:pharmacology*; D002148:Calmodulin-Binding Proteins / Q000494:pharmacology; D003432:Cross-Linking Reagents; D008840:Microfilament Proteins; D015879:Myosin Subfragments / Q000378:metabolism; D009218:Myosins / Q000037:antagonists & inhibitors*; D011817:Rabbits; D013050:Spectrometry, Fluorescence; D013329:Structure-Activity Relationship; D014335:Tropomyosin / Q000378:metabolism / Q000494:pharmacology; D014336:Troponin / Q000494:pharmacology; D000096985:Calponins
chemical_list: D000199:Actins; D017301:Ca(2+) Mg(2+)-ATPase; D002135:Calcium-Binding Proteins; D002148:Calmodulin-Binding Proteins; D003432:Cross-Linking Reagents; D008840:Microfilament Proteins; D015879:Myosin Subfragments; D009218:Myosins; D014335:Tropomyosin; D014336:Troponin; D000096985:Calponins