title: Irreversible thiophosphorylation and activation of tension in functionally skinned rabbit ileum strips by [35S]ATP gamma S.
abstract: Rabbit ileum strips were functionally skinned by exposure to staphylococcal alpha-toxin. Incubation of the strips in the ATP analog ATP gamma S or [35S]ATP gamma S in the presence of Ca2+ (but not in the absence of Ca2+) resulted in a maximal Ca2+-insensitive activated tension that persisted following removal of Ca2+. Correlated with this tension was 35S-labeling of the 20,000-dalton myosin light chain, LC20, that persisted even after removal of Ca2+. Tension in these strips partially relaxed when exposed to ATP (alpha,beta-methylene). In contrast, alpha-toxin-treated strips exposed to ATP or [gamma-32P]ATP showed Ca2+-sensitive, reversible activated tension and reversible 32P-labeling of the LC20. These results are consistent with a currently proposed model of Ca2+ control of smooth muscle contraction involving a myosin light chain kinase-phosphatase system.
mesh_terms: D000199:Actins / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D007082:Ileum / Q000502:physiology*; D007700:Kinetics; D008970:Molecular Weight; D009119:Muscle Contraction / Q000187:drug effects*; D009218:Myosins / Q000378:metabolism; D010766:Phosphorylation; D011817:Rabbits; D013873:Thionucleotides / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D000199:Actins; D013873:Thionucleotides; D000255:Adenosine Triphosphate; D009218:Myosins; D002118:Calcium