Plasma membrane calcium pump isoform 4a has a longer calmodulin-binding domain than 4b

Anil K. Verma, Agnes Enyedi, Adelaida G. Filoteo, Emanuel E. Strehler, John T. Penniston

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31 Scopus citations


Alternate splicing of human plasma membrane calcium pump isoform 4 (hPMCA4) transcripts causes the expression of two variants, hPMCA4a and hPMCA4b, which have different downstream regulatory regions. Of the two, hPMCA4a has a lower affinity for calmodulin and a lower effective affinity for Ca2+ (Enyedi, A. Verma, A. K., Heim, R. Adamo, H. P., Filoteo, A. G., Strehler, E. E., and Penniston, J. T. (1994) J. Biol. Chem. 269, 41-43). Additional consequences of the alternate splice were studied by analyzing the characteristics of constructs (expressed in COS-1 cells) containing different portions of the carboxyl terminus of hPMCA4a. Our results show striking differences in the structure of the calmodulin-binding and autoinhibitory domains of the two variants. The calmodulin-binding region of hPMCA4b is a region of about 28 residues, whereas that of hPMCA4a is about 49 residues long and is probably interrupted by a region not involved in the binding. The autoinhibitory region of hPMCA4b (a part of the downstream region that keeps the molecule inactive in the absence of Ca2+-calmodulin) is divided between the 28-residue calmodulin-binding region and a downstream region, whereas in hPMCA4a, all of it is contained within the 40-residue calmodulin-binding region.

Original languageEnglish (US)
Pages (from-to)3714-3718
Number of pages5
JournalJournal of Biological Chemistry
Issue number7
StatePublished - Feb 16 1996

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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