title: Studies on the amino groups of myosin ATPase. III. Effect of nucleotides on the fluorescence of beta-naphthoquinone-4-sulfonate bound to amino groups of myosin.
abstract: beta-Naphthoquinone-4-sulfonate was used for chemical modification of amino groups of myosin. The reagent was found to affect also the sulfhydryl groups if the reaction was not prevented by previous disulfide exchange with cystamine. When cystamine protection was employed the ATPase (ATP phosphohydrolase, EC3.6.1.3) activity was enhanced in the presence of Mg2+ and decreased in the presence of K+ or Ca2+, a pattern typical of myosin with blocked essential amino groups. On addition of ATP or ADP a blueshift was observed in the fluorescent emission spectrum of beta-naphthoquinone-4-sulfonate bound by myosin, presumably owing to conformational changes in the environment of essential amino groups induced by the binding of nucleotides.
mesh_terms: D000227:Adenine Nucleotides / Q000494:pharmacology*; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000596:Amino Acids; D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000494:pharmacology; D004789:Enzyme Activation; D005456:Fluorescent Dyes; D008274:Magnesium / Q000494:pharmacology; D009218:Myosins / Q000378:metabolism; D009285:Naphthoquinones; D011188:Potassium / Q000494:pharmacology; D011487:Protein Conformation / Q000187:drug effects; D011817:Rabbits; D013050:Spectrometry, Fluorescence; D013438:Sulfhydryl Compounds
chemical_list: D000227:Adenine Nucleotides; D000596:Amino Acids; D005456:Fluorescent Dyes; D009285:Naphthoquinones; D013438:Sulfhydryl Compounds; D000251:Adenosine Triphosphatases; D009218:Myosins; D008274:Magnesium; D011188:Potassium; D002118:Calcium