title: Role of ATP in the binding of caldesmon to smooth muscle myosin.
abstract: We have reported earlier that ATP causes both an increase in the affinity of caldesmon for smooth muscle myosin and a change in stoichiometry from 2 caldesmon molecules per myosin to 1:1 (Hemric & Chalovich, 1990). We now show that this ATP effect does not occur with skeletal muscle myosin, indicating that ATP has a specific effect on the structure of filamentous smooth muscle myosin. This ATP effect does not appear to be due to stabilization of a 10S type of filamentous smooth muscle myosin like that reported earlier (Ikebe & Hartshorne, 1984) since neither phosphorylation nor extensive modification of myosin with MalNEt (both which stabilize the 6S state of monomeric myosin) eliminates the effect of ATP. Caldesmon does bind more tightly to a form of smooth muscle myosin which is resistant to papain digestion. These results suggest that the ATP effect is due to stabilization of a local conformation of smooth muscle myosin which is independent of the larger 10S/6S conformational change (Suzuki et al., 1988). In the presence of ATP, the two heads of smooth muscle muscle myosin and the S-2 region form a single, higher affinity binding region for caldesmon.
authors.affiliation: Department of Biochemistry, East Carolina University, School of Medicine, Greenville, North Carolina 27858-4354, USA.
authors.forename: F W
authors.initials: FW
authors.lastname: Lu
authors.forename: J M
authors.initials: JM
authors.lastname: Chalovich
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002148:Calmodulin-Binding Proteins / Q000378:metabolism*; D002645:Chickens; D066298:In Vitro Techniques; D009130:Muscle, Smooth / Q000378:metabolism; D009218:Myosins / Q000378:metabolism*; D010206:Papain / Q000494:pharmacology; D011485:Protein Binding; D011487:Protein Conformation
chemical_list: D002148:Calmodulin-Binding Proteins; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D010206:Papain; D009218:Myosins