ISSN:
1432-1424
Keywords:
Key words: Skeletal muscle — Sarcoplasmic reticulum — Calcium release channel — Ryanodine receptor — Calmodulin — Sulfhydryl oxidation
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Abstract. The modulation of the calmodulin-induced inhibition of the calcium release channel (ryanodine receptor) by two sulfhydryl oxidizing compounds, 4-(chloromercuri)phenyl–sulfonic acid (4-CMPS) and 4,4′-dithiodipyridine (4,4′-DTDP) was determined by single channel current recordings with the purified and reconstituted calcium release channel from rabbit skeletal muscle sarcoplasmic reticulum (HSR) and [3H]ryanodine binding to HSR vesicles. 0.1 μm CaM reduced the open probability (P o ) of the calcium release channel at maximally activating calcium concentrations (50–100 μm) from 0.502 ± 0.02 to 0.137 ± 0.022 (n= 28), with no effect on unitary conductance. 4-CMPS (10–40 μm) and 4,4′-DTDP (0.1–0.3 mm) induced a concentration dependent increase in P o (〉 0.9) and caused the appearance of longer open states. CaM shifted the activation of the calcium release channel by 4-CMPS or 4,4′-DTDP to higher concentrations in single channel recordings and [3H]ryanodine binding. 40 μm 4-CMPS induced a near maximal (P o 〉 0.9) and 0.3 mm 4,4′-DTDP a submaximal (P o = 0.74) channel opening in the presence of CaM, which was reversed by the specific sulfhydryl reducing agent DTT. Neither 4-CMPS nor 4,4′-DTDP affected Ca-[125I]calmodulin binding to HSR. 1 mm MgCl2 reduced P o from 0.53 to 0.075 and 20–40 μm 4-CMPS induced a near maximal channel activation (P o 〉 0.9). These results demonstrate that the inhibitory effect of CaM or magnesium in a physiological concentration is diminished or abolished at high concentrations of 4-CMPS or 4,4′-DTDP through oxidation of activating sulfhydryls on cysteine residues of the calcium release channel.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s002320001036
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