Sodium ions as substitutes for protons in the gastric H,K-ATPase

Journal Article · Wed Oct 25 00:00:00 EDT 1989 · Journal of Biological Chemistry; (USA)

OSTI ID:5132409

Polvani, C; Sachs, G; Blostein, R ^[1]

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1. McGill Univ., Montreal, Quebec (Canada)

In view of the striking homology among various ion-translocating ATPases including Na,K-ATPase, Ca-ATPase, and H,K-ATPase, and the recent evidence that protons can replace cytoplasmic sodium as well as potassium in the reaction mechanism of the Na,K-ATPase (Polvani, C., and Blostein, R. (1988) J. Biol. Chem. 263, 16757-16763), we studied the role of sodium as a substitute for protons in the H,K-ATPase reaction. Using hog gastric H,K-ATPase-rich inside-out membrane vesicles we observed 22Na+ influx which was stimulated by intravesicular potassium ions (K+i) at pH 8.5 but not at pH 7.1. This sodium influx was observed in medium containing ATP and was inhibited by vanadate and SCH28080, a selective inhibitor of the gastric H,K-ATPase. At least 2-fold accumulation of sodium was observed at pH 8.5. Experiments aimed to determine the sidedness of the alkaline pH requirement for K+i-dependent sodium influx showed that K+i-activated sodium influx depends on pHout and is unaffected by changes in pHin. These results support the conclusion that sodium ions substitute for protons in the H,K-ATPase reaction mechanism and provide evidence for a similarity in ion selectivity and/or binding domains of the Na,K-ATPase and the gastric H,K-ATPase enzymes.

• OSTI ID: 5132409
• Journal Information: Journal of Biological Chemistry; (USA), Vol. 264:30; ISSN 0021-9258
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
ATP-ASE
BIOCHEMICAL REACTION KINETICS
SODIUM COMPOUNDS
BIOLOGICAL FUNCTIONS
ATP
CATIONS
ENZYME INHIBITORS
PH VALUE
POTASSIUM COMPOUNDS
PROTONS
SODIUM 22
SWINE
TRACER TECHNIQUES
ACID ANHYDRASES
ALKALI METAL COMPOUNDS
ALKALI METAL ISOTOPES
ANIMALS
BARYONS
BETA DECAY RADIOISOTOPES
BETA-PLUS DECAY RADIOISOTOPES
CHARGED PARTICLES
DOMESTIC ANIMALS
ELEMENTARY PARTICLES
ENZYMES
FERMIONS
FUNCTIONS
HADRONS
HYDROLASES
IONS
ISOMERIC TRANSITION ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LIGHT NUCLEI
MAMMALS
NUCLEI
NUCLEONS
NUCLEOTIDES
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
PHOSPHOHYDROLASES
RADIOISOTOPES
REACTION KINETICS
SODIUM ISOTOPES
VERTEBRATES
YEARS LIVING RADIOISOTOPES
550201* - Biochemistry- Tracer Techniques