title: Evidence for an altered structure of actin-S1 complexes when Mg-adenylylimidodiphosphate binds.
abstract: Simultaneous measurements of actin-S1 binding and light scatter (or turbidity) were made in the presence and absence of saturating Mg-adenylylimidodiphosphate (Mg.AMP.PNP). It was found that if the actin was covalently labelled on cysteine 363 by dansyl aziridine (DAZ) the ternary complex DAZactin-S1-Mg.AMP.PNP scattered 36% less light than the binary complex DAZactin-S1. If the actin was not labelled there was no difference in scatter. The decrease in scatter of DAZactin-S1 was dependent on Mg.AMP.PNP concentration in a hyperbolic manner with half maximal decrease at 40 micrometers. No change in light scatter by DAZactin-S1 was found when H.AMP.PNP or Mg.ADP bound. The change in light scatter is evidence that the structure of DAZactin-S1 is altered when Mg.AMP.PNP binds. The possible nature of the structural change and its role in chemo-mechanical transduction is discussed.
mesh_terms: D000199:Actins / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives*; D000266:Adenylyl Imidodiphosphate / Q000378:metabolism*; D000818:Animals; D002474:Cell-Free System; D006874:Hydrostatic Pressure; D007460:Iodoacetamide; D007700:Kinetics; D008274:Magnesium / Q000378:metabolism; D015879:Myosin Subfragments; D009218:Myosins / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D011817:Rabbits
chemical_list: D000199:Actins; D015879:Myosin Subfragments; D010446:Peptide Fragments; D000266:Adenylyl Imidodiphosphate; D000255:Adenosine Triphosphate; D009218:Myosins; D008274:Magnesium; D007460:Iodoacetamide