title: Differential response of fast and slow myosin ATPase from skeletal muscle to F-actin and to phalloidin F-actin.
abstract: Fast muscle myosin responds in similar way to F-actin and to phalloidin F-actin. It is activated 7.5 fold at infinite F-actin concentration and 6.8 fold at infinite phalloidin F-actin. The actomyosin dissociation constants are 0.89 +/- 0.34 microM with F-actin and 0.90 +/- 0.71 microM with phalloidin F-actin. Slow muscle myosin responds differently to F-actin and to phalloidin F-actin. It is activated 3.76 fold at infinite F-actin concentration and only 2.27 fold at infinite phalloidin F-actin concentration. The actomyosin dissociation constants are 1.95 +/- 1.27 microM with F-actin and 0.27 +/- 0.16 microM with phalloidin F-actin. At first glance this means that substitution of F-actin with phalloidin F-actin magnifies the difference between fast muscle and slow muscle myosins. Furthermore the change of the dissociation constants may affect the contractile force of the attached crossbridge.
authors.affiliation: Dipartimento di Biochimica e Biologia Molecolare, Università di Ferrara, via Borsari 46, 44100 Ferrara, Italy.
authors.forename: Giorgio
authors.initials: G
authors.lastname: Trombetta
authors.forename: Raffella
authors.initials: R
authors.lastname: Adami
authors.forename: Orietta
authors.initials: O
authors.lastname: Cintio
authors.forename: Enrico
authors.initials: E
authors.lastname: Grazi
mesh_terms: D000199:Actins / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D004789:Enzyme Activation; D018482:Muscle, Skeletal / Q000201:enzymology*; D009218:Myosins / Q000378:metabolism*; D010590:Phalloidine / Q000737:chemistry; D011817:Rabbits
chemical_list: D000199:Actins; D010590:Phalloidine; D009218:Myosins