title: Interaction between two myosin heads in acto-smooth muscle heavy meromyosin rigor complex.
abstract: Muscle contraction occurs as a result of the cyclic interaction between actin and myosin, coupled with the hydrolysis of ATP by the myosin heads. A myosin molecule consists of two globular heads and a rod-shaped tail. It is thought that each myosin head functions as a contractile machinery unit, because each head shows ATPase activity and binds to F-actin. A still unsolved question is whether or not the two heads of a myosin molecule interact with each other during their cyclic interaction with F-actin. Here we report that when chicken gizzard heavy meromyosin (HMM) in its rigor complex with F-actin is reacted with the zero-length cross-linker 1-ethyl-3-[3-(dimethylamino)propyl] carbodiimide (EDC), the two heads of the HMM molecule are cross-linked. This result suggests that the two heads of smooth muscle myosin are in contact with each other when myosin is attached to F-actin. It is thus possible that the two myosin heads interact with each other when cross-bridges are formed.
authors.affiliation: Department of Structural Analysis, National Cardiovascular Center Research Institute, Osaka, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Onishi
mesh_terms: D000818:Animals; D002645:Chickens; D003432:Cross-Linking Reagents / Q000494:pharmacology; D005022:Ethyldimethylaminopropyl Carbodiimide / Q000494:pharmacology; D005895:Gizzard, Avian / Q000737:chemistry / Q000502:physiology; D009119:Muscle Contraction / Q000502:physiology*; D009130:Muscle, Smooth / Q000737:chemistry / Q000502:physiology*; D015879:Myosin Subfragments / Q000737:chemistry / Q000502:physiology*
chemical_list: D003432:Cross-Linking Reagents; D015879:Myosin Subfragments; D005022:Ethyldimethylaminopropyl Carbodiimide