Mutants in the putative nucleotide-binding region of the plasma membrane Ca2+-pump. A reduction in activity due to slow dephosphorylation

H. P. Adamo, A. G. Filoteo, A. Enyedi, J. T. Penniston

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14 Citations (Scopus)

Abstract

Mutants of individual residues of the plasma membrane Ca2+-pump were made in the highly conserved region that (in related P-type ATPases) has been associated with nucleotide binding. Alteration of the strictly conserved Asp672 to Glu nearly eliminated the ability of the pump to transport Ca2+, while alteration at Val674, Arg675, and Lys686 reduced the activity. High levels of ATP (25 mM) did not overcome the reduced activity, indicating that it could not be due to a reduction in the affinity for ATP. Effects not directly related to ATP binding seemed to result from mutations in this area. For instance, the amount of phosphorylated intermediate in the most severely inhibited mutant, Asp672 → Glu, was nearly as high as that in the wild type, a much larger amount of phosphorylated intermediate than was expected from its low activity. However, the rate of decomposition of this intermediate was much slower than that of the wild type, indicating that the inhibition of this mutant resulted from an inhibition of the E ~ P → E step in the enzyme cycle.

Original languageEnglish
Pages (from-to)30111-30114
Number of pages4
JournalJournal of Biological Chemistry
Volume270
Issue number50
DOIs
Publication statusPublished - Dec 1 1995

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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