title: Actions of sulfhydryl reagents on single ryanodine receptor Ca(2+)-release channels from sheep myocardium.
abstract: Effects of the reactive disulfides, 2,2'- and 4,4'-dithiodipyridine, on single cardiac ryanodine receptor (RyR) ion channels incorporated into lipid bilayers are reported. RyRs are activated within minutes of addition of the reactive disulfides (10(-7) to 10(-3) M) with an irreversible loss of channel activity after the activation at concentrations > or = 10(-4) M. This activation, followed by loss of activity, is seen over a wide range of cytoplasmic (cis) Ca2+ concentration between 10(-9) and 2 x 10(-2) M and occurs more rapidly with higher reactive disulfide concentrations or when RyRs are initially active at 10(-5) or 10(-3) M Ca2+. The reactive disulfides increase the channel open probability by introducing long components into the open time distributions, increasing the mean channel open time by up to 50-fold. Closed time distributions are not altered by the sulfhydryl reagents. The effects of the reactive disulfides are prevented by the reducing agents dithiothreitol and glutathione (1-10 mM). The results suggest that cysteine residues on the RyR complex can regulate the ion channel gating mechanisms.
authors.affiliation: Muscle Research Group, John Curtin School of Medical Research, Canberra City, Australian Capital Territory, Australia.
authors.forename: K R
authors.initials: KR
authors.lastname: Eager
authors.forename: L D
authors.initials: LD
authors.lastname: Roden
authors.forename: A F
authors.initials: AF
authors.lastname: Dulhunty
mesh_terms: D015082:2,2'-Dipyridyl / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D004220:Disulfides / Q000494:pharmacology*; D006321:Heart / Q000502:physiology*; D007700:Kinetics; D008051:Lipid Bilayers; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008861:Microsomes / Q000187:drug effects / Q000502:physiology*; D008954:Models, Biological; D009124:Muscle Proteins / Q000187:drug effects / Q000502:physiology*; D009206:Myocardium / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology*; D019837:Ryanodine Receptor Calcium Release Channel; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000502:physiology*; D012756:Sheep; D013439:Sulfhydryl Reagents / Q000494:pharmacology*
chemical_list: D015220:Calcium Channels; D004220:Disulfides; D008051:Lipid Bilayers; D009124:Muscle Proteins; D011725:Pyridines; D019837:Ryanodine Receptor Calcium Release Channel; D013439:Sulfhydryl Reagents; C001105:2,2'-dipyridyl disulfide; C007542:4,4'-dipyridyl disulfide; D015082:2,2'-Dipyridyl; D002118:Calcium