Kinetic Characterization of Ca2+ Transport in Synaptic Membranes

M. A. Javors, C. L. Bowden, D. H. Ross

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39 Scopus citations

Abstract

Abstract: Lysed synaptosomal membranes were prepared from brain cortices of HA/ICR Swiss mice, and the ATP‐stimulated Ca2+ uptake, Ca2+‐stimulated Mg2+ ‐dependent ATPase activity, and the Ca2+‐stimulated acyl phosphorylation of these membranes were studied. The Km values for free calcium concentrations ([Ca2+]f) for these processes were 0.50 μM, 0.40 μM, and 0.31 μM, respectively. Two kinetically distinct binding sites for ATP were observed for the ATP‐stimulated Ca2+ uptake and the Ca2+‐stimulated Mg2+‐ATPase activity. The high‐affinity Km values for ATP for these two processes were 16.3 μM, and 28 μM, respectively. These results indicate that the processes studied operate in similar physiological concentration ranges for the substrates [Ca2+]f and ATP under identical assay conditions and, further, that these processes may be functionally coupled in the membrane.

Original languageEnglish (US)
Pages (from-to)381-387
Number of pages7
JournalJournal of Neurochemistry
Volume37
Issue number2
DOIs
Publication statusPublished - Aug 1981

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Keywords

  • ATP‐dependent Ca uptake
  • Ca transport protein
  • Cation transport
  • Ca‐Mg‐ATPase activity
  • Ca‐stimulated acyl phosphorylation

ASJC Scopus subject areas

  • Biochemistry
  • Cellular and Molecular Neuroscience

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