Biphasic modulation of ryanodine binding to sarcoplasmic reticulum vesicles of skeletal muscle by Zn2+ ions

Ruo Hong Xia, Xiao Yang Cheng, Hui Wang, Ke Ying Chen, Qin Qin Wei, Xiao Hui Zhang, Pei Hong Zhu

Research output: Contribution to journalArticle

12 Scopus citations

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 inhibition 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 K(d), whereas both an increase in K(d) and a possible decrease in B(max) 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.

Original languageEnglish (US)
Pages (from-to)279-286
Number of pages8
JournalBiochemical Journal
Volume345
Issue number2
DOIs
StatePublished - Jan 15 2000
Externally publishedYes

Keywords

  • Binding assay
  • Ca
  • Caffeine
  • Dithiothreitol
  • Ryanodine receptor

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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