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In Bovine Heart Na + /Ca 2+ Exchanger Maximal Ca 2+ i Affinity Requires Simultaneously High pH i and PtdIns‐4,5‐P2 Binding to the Carrier
Author(s) -
POSADA VELIA,
BEAUGÉ LUIS,
BERBERIÁN GRACIELA
Publication year - 2007
Publication title -
annals of the new york academy of sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.712
H-Index - 248
eISSN - 1749-6632
pISSN - 0077-8923
DOI - 10.1196/annals.1387.010
Subject(s) - chemistry , intracellular , deprotonation , isotopes of calcium , biophysics , calcium , analytical chemistry (journal) , ion , biochemistry , chromatography , biology , organic chemistry
Na + i ‐dependent Ca 2+ uptake, Na + ‐dependent Ca 2+ release, and PtdIns‐4,5‐P2 binding to Na + /Ca 2+ exchanger (NCX1) as a function of extravesicular (intracellular) [Ca 2+ ] were measured. Alkalinization increases Ca 2+ i affinity and PtdIns‐4,5‐P2 bound to NCX1; these effects are abolished by pretreatment with PtdIns‐PLC and are insensitive to MgATP. Acidification reduces Ca 2+ i affinity. MgATP reverts it only partially despite the fact that the PtdIns‐4,5‐P2 bound to NCX1 reaches the same levels as at pH 7.8. Extravesicular Na + ‐stimulated and Ca 2+ ‐dependent Ca 2+ efflux indicate the Ca 2+ regulatory site is involved. Therefore, to display maximal affinity to Ca 2+ i , PtdIns‐4,5‐P2 binding and deprotonation of NCX1 are simultaneously need.