Mechanism of cis- and trans-substrate interactions at the tetraethylammonium/H+ exchanger of rabbit renal brush-border membrane vesicles

Journal Article · Sun Dec 25 04:00:00 EST 1988 · J. Biol. Chem.; (United States)

OSTI ID:6611737

Wright, S H; Wunz, T M

The kinetic basis for trans-effects of intravesicular substrates on the uptake of the organic cation, tetraethylammonium (TEA), into rabbit renal brush-border membrane vesicles (BBMV) was studied. Preloading BBMV with 1, 2, or 4 mM TEA stimulated the initial rate of uptake and the total net accumulation of 0.1 mM (TH)TEA. The stimulatory effect of intravesicular TEA on the initial rate of uptake was a saturable function of the trans-TEA concentration, with a half-maximal effect noted at an intravesicular concentration of 0.28 mM. A 1 mM trans-concentration of TEA increased the Jmax of (TH)TEA uptake (from 4.3 to 6.8 nmol.mg-1.min-1) without affecting the apparent Kt. An outwardly directed H+ gradient also increased Jmax (to 10.7 nmol.mg-1.min-1), although the addition of an outwardly directed TEA gradient did not produce further increases in the rate of TEA uptake. External H+ acted as a competitive inhibitor of TEA uptake, and an increase in external (H+) (from 32 nM to 100 nM) produced an increase in the apparent Kt for TEA transport (from 0.12 to 0.26 mM) without affecting the Jmax. The results suggested that TEA and H+ compete for a common site or set of mutually exclusive sites on the cytoplasmic and luminal aspects of TEA/H+ exchanger in the renal brush border, and that these sites have a similar affinity for TEA.

• Research Organization: Univ. of Arizona, Tucson (USA)
• OSTI ID: 6611737
• Journal Information: J. Biol. Chem.; (United States), Journal Name: J. Biol. Chem.; (United States) Vol. 263:36; ISSN JBCHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AMMONIUM COMPOUNDS
ANIMALS
BARYONS
BIOCHEMICAL REACTION KINETICS
BODY
CELL CONSTITUENTS
CELL MEMBRANES
CHARGED PARTICLES
ELEMENTARY PARTICLES
FERMIONS
HADRONS
HYDROGEN IONS
IONS
ISOTOPE APPLICATIONS
KIDNEYS
KINETICS
LABELLED COMPOUNDS
MAMMALS
MEMBRANE TRANSPORT
MEMBRANES
NUCLEONS
ORGANS
PROTONS
RABBITS
REACTION KINETICS
SUBSTRATES
TRACER TECHNIQUES
TRITIUM COMPOUNDS
UPTAKE
VERTEBRATES