title: Perturbations of functional interactions with myosin induce long-range allosteric and cooperative structural changes in actin.
abstract: The role of the rotational dynamics of actin filaments in their interaction with myosin was studied by comparing the effect of myosin subfragment 1 (S1) with two other structural perturbations, which have substantial inhibitory effects on activation of myosin ATPase and in vitro motility of F-actin: (1) binding of the antibody fragment Fab(1-7) against the first seven N-terminal residues and (2) copolymerization with monomers treated with the zero-length cross-linker 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide (EDC), referred to as EDC-actin. The rotational motion of actin was measured by time-resolved phosphorescence anisotropy (TPA) of erythrosin iodoacetamide (ErIA) attached to Cys 374 on actin. The binding of S1 in a rigor complex (no nucleotide) induced intramonomer (allosteric) and intermonomer (cooperative) structural changes that increased the residual anisotropy of labeled F-actin, indicating a conformational change in the region of the C terminus. Similar allosteric and cooperative changes were induced by binding of Fab(1-7) and by copolymerization of the ErIA-labeled actin monomers with EDC-actin. This suggests that the functional perturbations transform actin to a form resembling the rigor actomyosin complex. The correlation of the perturbation-induced changes in TPA of actin with the functional effects suggests that the actomyosin interaction can be inhibited by stabilization of actin in one of its structural intermediates.
authors.affiliation: Department of Biochemistry, University of Minnesota Medical School, Minneapolis, Minnesota 55455, USA.
authors.forename: E
authors.initials: E
authors.lastname: Prochniewicz
authors.forename: D D
authors.initials: DD
authors.lastname: Thomas
mesh_terms: D000199:Actins / Q000737:chemistry* / Q000378:metabolism*; D000494:Allosteric Regulation; D000495:Allosteric Site; D000818:Animals; D005022:Ethyldimethylaminopropyl Carbodiimide; D007700:Kinetics; D008163:Luminescent Measurements; D046911:Macromolecular Substances; D008956:Models, Chemical; D018482:Muscle, Skeletal / Q000378:metabolism; D015879:Myosin Subfragments / Q000737:chemistry* / Q000378:metabolism*; D009218:Myosins / Q000378:metabolism*; D011487:Protein Conformation; D011817:Rabbits
chemical_list: D000199:Actins; D046911:Macromolecular Substances; D015879:Myosin Subfragments; D009218:Myosins; D005022:Ethyldimethylaminopropyl Carbodiimide