title: Binding of F-actin to a region between SH1 and SH2 groups of myosin subfragment-1 which may determine the high affinity of acto-subfragment-1 complex at rigor.
abstract: Covalent cross-linking reaction between SH1 and SH2 groups in myosin subfragment-1 (S-1) by N,N'-p-phenylenedimaleimide (pPDM) was followed by the degree of inactivation of NH4+-EDTA ATPase activity. The rate of the cross-linking reaction decreased to less than a 20th in the presence of F-actin. The inhibitory effect of F-actin was not observed in the presence of MgATP. Binding of F-actin to S-1 was measured using ultracentrifugation. S-1 whose SH1 and SH2 were covalently cross-linked by pPDM or 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) did not bind F-actin. After the DTNB-cross-linked S-1 is reduced by dithiothreitol, the ability to bind F-actin is recovered. These results suggest that S-1 has a binding site for F-actin in the region between SH1 and SH2. This site appears to determine the high affinity of acto-S-1 complex at the rigor while decreasing the affinity more than 10(2) times in the presence of MgATP.
mesh_terms: D000199:Actins / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism*; D055598:Chemical Phenomena; D002621:Chemistry; D003432:Cross-Linking Reagents; D004228:Dithionitrobenzoic Acid; D008301:Maleimides / Q000494:pharmacology; D008840:Microfilament Proteins; D009127:Muscle Rigidity / Q000378:metabolism; D015879:Myosin Subfragments; D009218:Myosins / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism*; D011817:Rabbits; D013438:Sulfhydryl Compounds / Q000378:metabolism
chemical_list: D000199:Actins; D002352:Carrier Proteins; D003432:Cross-Linking Reagents; C034037:F-actin-binding proteins; D008301:Maleimides; D008840:Microfilament Proteins; D015879:Myosin Subfragments; D010446:Peptide Fragments; D013438:Sulfhydryl Compounds; D000255:Adenosine Triphosphate; D004228:Dithionitrobenzoic Acid; C011328:N,N'-4-phenylenedimaleimide; D009218:Myosins; D000252:Calcium-Transporting ATPases