PMID: 2105743Jan 16, 1990Paper

Kinetic properties of the K+/H+ antiport of heart mitochondria

Biochemistry
G P Brierley, D W Jung

Abstract

The fluorescence of 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF) has been used to follow a K(+)-dependent alkaline shift in the matrix pH (pHi) of isolated heart mitochondria. The K(+)-dependent pHi change has properties consistent with an inward exchange of K+ for matrix H+ on the K+/H+ antiport of the mitochondrion. The reaction is activated by depletion of matrix Mg2+ with A23187 and by an alkaline external pH (pHo) and hypotonic conditions. The exchange is inhibited by quinine, dicyclohexylcarbodiimide, and exogenous Mg2+, but not by Li+. The rate of K+/H+ antiport measured in this way increases with increasing pHo to a maximum near pHo 9. The rate is a hyperbolic function of [K+] at pHo values above 8.3 with an apparent Km of 30 mM at pHo 8.4 and 14 mM at pHo 8.8. External H+ acts as a mixed-type inhibitor of the K+/H+ antiport under these conditions with a Ki equivalent to pHo 8.6-8.8. When pHo is kept constant, the reaction is relatively insensitive to matrix pH (pHi) in the range from 7.0 to 7.5. Above this pHi, the K(+)-dependent H+ extrusion shows a hyperbolic dependence on [H+]i with an apparent Km equivalent to pHi 8.1. The activated antiport shows an affinity sequence of Li+ greater than K+ = Rb+ greater...Continue Reading

Citations

Jan 7, 2010·PLoS Computational Biology·Jason N BazilAnn E Rundell
Oct 24, 2006·The Journal of Biological Chemistry·Natalia ShalbuyevaNickolay Brustovetsky
Oct 1, 1994·Journal of Bioenergetics and Biomembranes·G P BrierleyD W Jung
Apr 21, 2020·BMC Molecular and Cell Biology·Olga AkopovaVadim Sagach
Jan 11, 2021·Biochimica Et Biophysica Acta. Bioenergetics·Shane Austin, Karin Nowikovsky
May 11, 1995·The American Journal of Physiology·M SastrasinhS Sastrasinh
Aug 1, 1996·The International Journal of Biochemistry & Cell Biology·A SzewczykM J Nałecz
Aug 1, 1991·Archives of Biochemistry and Biophysics·G P BrierleyD W Jung
Jul 25, 2006·Journal of Theoretical Biology·Alexandra V PokhilkoEkhson L Holmuhamedov
Aug 22, 2021·Biophysical Chemistry·Igor Khmelinskii, Vladimir Makarov

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