Exchange of calcium between muscle Ca2+-binding proteins

Hans J. Moeschler, Dean A. Malencik, Sitivad Pocinwong, Olusola Alaba, Glenn L. Kerrick, Edmond H. Fischer

Research output: Contribution to journalArticle

9 Scopus citations

Abstract

Sarcoplasmic reticulum isolated from skeletal muscle of the rabbit and the Pacific dogfish (Squalus acanthias) was characterized in terms of its Ca2+-uptake at different temperatures. SR from both species showed comparable Ca2+-uptake rates at their basal body temperatures (5°C and 37°C, respectively). Only very low percentages of phosphorylase, phosphorylase kinase and phosphatase were found to be associated with the purified vesicles, once these were freed of contaminating glycogen particles. Ca2+-fluxes during contraction/relaxation-cycles in muscles were studied in a reconstituted system by measuring the inhibition of the rate of Ca2+-uptake by the sarcoplasmic reticulum and of the Ca2+-dependent activity of phosphorylase kinase, respectively, by metal-free troponin, troponin-C, parvalbumin and phosphorylase kinase; EGTA was used as an internal standard. Ca2+-binding capacities of the various proteins were determined separately by gel filtration experiments. Data obtained agreed with published values for troponin, troponin-C and parvalbumin; for phosphorylase kinase, a value of n- = 8 was found regardless of the state of phosphorylation of the enzyme. Results obtained from both types of experiments established apparent Ca2+-affinities in the following decreasing order : phosphorylase kinase ∼ parvalbumin > EGTA > troponintroponin-C, with no difference found between the non-phosphorylated and phosphorylated forms of phosphorylase kinase. Apparent equilibrium constants for these Ca2+-complexes, relative to EGTA, were in agreement with published values obtained from classical equilibrium studies. Similar results were obtained with proteins isolated from rabbit and dogfish muscle. No indication of protein-protein interactions affecting Ca2+-fluxes could be found in such a reconstituted system, except for the singular case of a slight increased inhibition of phosphorylase kinase by parvalbumin following phosphorylation of the enzyme.

Original languageEnglish (US)
Pages (from-to)615-624
Number of pages10
JournalBiochimie
Volume61
Issue number5-6
DOIs
StatePublished - Sep 10 1979
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry

Fingerprint Dive into the research topics of 'Exchange of calcium between muscle Ca<sup>2+</sup>-binding proteins'. Together they form a unique fingerprint.

  • Cite this

    Moeschler, H. J., Malencik, D. A., Pocinwong, S., Alaba, O., Kerrick, G. L., & Fischer, E. H. (1979). Exchange of calcium between muscle Ca2+-binding proteins. Biochimie, 61(5-6), 615-624. https://doi.org/10.1016/S0300-9084(79)80159-5