In:
Biochemical Journal, Portland Press Ltd., Vol. 345, No. 2 ( 2000-01-15), p. 279-286
Abstract:
With the use of a [3H]ryanodine binding assay, the modulation of skeletal muscle ryanodine receptor (RyR1) by Zn2+ was investigated. In the presence of 100 μM free Ca2+ concentration ([Ca2+] f) as activator, the equilibrium [3H]ryanodine binding to heavy sarcoplasmic reticulum vesicles was biphasically modulated by Zn2+. The binding was increased by a free Zn2+ concentration ([Zn2+] f) of less than 1 μM; a peak binding, approx. 140% of the control (without added Zn2+) was obtained at 0.3 μM [Zn2+]f. An inhibitory effect of Zn2+ became obvious with a [Zn2+] f of more than 1 μM; the [Zn2+]f for producing half inhibi tion was 2.7±0.5 μM (mean±S.D.). Scatchard analysis indicated that the increase in the binding induced by low [Zn2+]f was due to a decrease in Kd, whereas both an increase in Kd and a possible decrease in Bmax were responsible for the decrease in binding induced by high [Zn2+] f. The binding in the presence of micromolar [Zn2+]f showed a biphasic time course. In the presence of 3 μM [Zn2+] f, after reaching a peak with an increased rate of initial binding, the binding gradually declined. The decline phase could be prevented by decreasing [Zn2+]f to 0.5 μM or by adding 2 mM dithiothreitol, a thiol-reducing agent. The [Ca2+] f dependence of binding was changed significantly by Zn2+, whereas Ca2+ had no clear effect on the [Zn2+]f dependence of binding. Moreover, some interactions were found in the effects between Zn2+ and other RyR1 modulators. It is indicated that Zn2+ can modulate the activation sites and inactivation sites for Ca2+ on RyR1. The physiological significance of the effects of Zn2+ on ryanodine binding is discussed.
Type of Medium:
Online Resource
ISSN:
0264-6021
,
1470-8728
Language:
English
Publisher:
Portland Press Ltd.
Publication Date:
2000
detail.hit.zdb_id:
1473095-9
SSG:
12
