title: Distinct structures of ATP and GTP complexes in the myosin ATPase.
abstract: The active site of the myosin subfragment-1 ATPase was affinity-labeled with ribose-modified fluorescent analogs of ADP, dADP, CDP, UDP, IDP, and GDP in combination with vanadate, forming a stable myosin-nucleoside diphosphate-vanadate complex that is analogous to the normal myosin-ADP-Pi intermediate [Hiratsuka, T. (1984) J. Biochem. 96, 147-154]. Labeled enzyme was isolated free of unbound analog and vanadate, and fluorescent properties of the fluorophore at the active site were examined. Fluorescence emission and acrylamide quenching studies revealed that the hydrophobicity of environment around the fluorophore and the degree of its burial in the protein vary with the base structure of NDP. It was found that the fluorophore of ADP analog is most buried into the protein, while that of the GDP analog is least buried. The results suggest that the deep burial of ATP into the myosin active site is essential for muscle contraction.
mesh_terms: D000178:Acrylamides; D000251:Adenosine Triphosphatases / Q000032:analysis*; D000255:Adenosine Triphosphate / Q000032:analysis*; D000345:Affinity Labels; D000818:Animals; D001665:Binding Sites; D005456:Fluorescent Dyes; D006160:Guanosine Triphosphate / Q000032:analysis*; D009132:Muscles / Q000201:enzymology; D009711:Nucleotides; D011817:Rabbits
chemical_list: D000178:Acrylamides; D000345:Affinity Labels; D005456:Fluorescent Dyes; D009711:Nucleotides; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases