title: Oxidation and reduction of pig skeletal muscle ryanodine receptors.
abstract: Time-dependent effects of cysteine modification were compared in skeletal ryanodine receptors (RyRs) from normal pigs and RyR(MH) (Arg(615) to Cys(615)) from pigs susceptible to malignant hyperthermia, using the oxidizing reagents 4,4'-dithiodipyridine (4, 4'-DTDP) and 5,5'-dithio-bis(2-nitrobenzoic acid) (DTNB) or the reducing agent dithiothreitol (DTT). Normal and RyR(MH) channels responded similarly to all reagents. DTNB (1 mM), either cytoplasmic (cis) or luminal (trans), or 1 mM 4,4'-DTDP (cis) activated RyRs, introducing an additional long open time constant. 4,4'-DTDP (cis), but not DTNB, inhibited channels after >5 min. Activation and inhibition were relieved by DTT (1-10 mM). DTT (10 mM, cytoplasmic or luminal), without oxidants, activated RyRs, and activation reversed with 1 mM DTNB. Control RyR activity was maintained with 1 mM DTNB and 10 mM DTT present on the same or opposite sides of the bilayer. We suggest that 1) 4,4'-DTDP and DTNB covalently modify RyRs by oxidizing activating or inhibiting thiol groups; 2) a modified thiol depresses mammalian skeletal RyR activity under control conditions; 3) both the activating thiols and the modified thiols, accessible from either cytoplasm or lumen, reside in the transmembrane region; 4) some cardiac sulfhydryls are unavailable in skeletal RyRs; and 5) Cys(615) in RyR(MH) is functionally unimportant in redox cycling.
authors.affiliation: Muscle Research Group, John Curtin School of Medical Research, Canberra, ACT 2601, Australia.
authors.forename: C S
authors.initials: CS
authors.lastname: Haarmann
authors.forename: R H
authors.initials: RH
authors.lastname: Fink
authors.forename: A F
authors.initials: AF
authors.lastname: Dulhunty
mesh_terms: D000818:Animals; D055592:Biophysical Phenomena; D001703:Biophysics; D003545:Cysteine / Q000737:chemistry; D004220:Disulfides; D004228:Dithionitrobenzoic Acid; D004229:Dithiothreitol; D066298:In Vitro Techniques; D008305:Malignant Hyperthermia / Q000235:genetics / Q000378:metabolism / Q000662:veterinary; D018482:Muscle, Skeletal / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism; D010084:Oxidation-Reduction; D017354:Point Mutation; D011725:Pyridines; D019837:Ryanodine Receptor Calcium Release Channel / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013439:Sulfhydryl Reagents; D013552:Swine; D013553:Swine Diseases / Q000235:genetics / Q000378:metabolism
chemical_list: D004220:Disulfides; D011725:Pyridines; D019837:Ryanodine Receptor Calcium Release Channel; D013439:Sulfhydryl Reagents; C007542:4,4'-dipyridyl disulfide; D004228:Dithionitrobenzoic Acid; D003545:Cysteine; D004229:Dithiothreitol