Oat tonoplast H/sup +//Ca/sup 2 +/ antiport is a reversible, electrogenic transport system

Conference · Tue Apr 01 04:00:00 EST 1986 · Plant Physiol.; (United States)

OSTI ID:5383154

Schumaker, K S; Sze, H

The oat root tonoplast H/sup +//Ca/sup 2 +/ antiport was characterized directly using an artificially generated pH gradient (acid inside). Tonoplast vesicles are isolated from a 0/4% dextran interface. These membranes are enriched in ATPase activity and ATP-dependent 45-Ca/sup 2 +/ uptake that are nitrate-sensitive and azide-resistant. Ca/sup 2 +/ uptake is coupled to the efflux of H/sup +/ as increasing Ca/sup 2 +/ concentrations could progressively dissipate a pH gradient. The Km of the antiport for Ca/sup 2 +/ is 10 ..mu..M. La/sup 3 +/ (50 ..mu..M), ruthenium red (25 ..mu..M) and N,N'-dicyclohexylcarbodiimide (3 ..mu..M) inhibited Ca/sup 2 +/ uptake but had no effect on the formation of ..delta..pH. The H/sup +//Ca/sup 2 +/ is electrogenic (generating a positive interior potential) as demonstrated by the uptake of (14-C)SCN/sup -/. Furthermore, an artificially imposed membrane potential (interior negative) stimulated Ca/sup 2 +/ uptake while a positive potential decreased uptake. The antiport is reversible as a Ca/sup 2 +/ gradient (Ca/sup 2 +//sub in/ > Ca/sup 2 +//sub out/) could drive formation of a pH gradient (acidic inside).

• Research Organization: Univ. of Maryland, College Park
• DOE Contract Number: AS05-82ER13015
• OSTI ID: 5383154
• Conference Information: Journal Name: Plant Physiol.; (United States) Journal Volume: 80:4
• Country of Publication: United States
• Language: English

Related Subjects

551001* -- Physiological Systems-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ACID ANHYDRASES
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METAL COMPOUNDS
ATP
ATP-ASE
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
CALCIUM 45
CALCIUM COMPOUNDS
CALCIUM ISOTOPES
CATIONS
CELL CONSTITUENTS
CELL MEMBRANES
CHARGED PARTICLES
DAYS LIVING RADIOISOTOPES
ENZYMES
EVEN-ODD NUCLEI
HYDROLASES
IMIDES
INTERMEDIATE MASS NUCLEI
IONS
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LABELLED COMPOUNDS
LANTHANUM COMPOUNDS
MEMBRANES
NITRATES
NITROGEN COMPOUNDS
NUCLEI
NUCLEOTIDES
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXYGEN COMPOUNDS
PH VALUE
PHOSPHOHYDROLASES
PHYSIOLOGY
PLANT CELLS
RADIOISOTOPES
RARE EARTH COMPOUNDS
REACTION KINETICS
REFRACTORY METAL COMPOUNDS
RESPONSE MODIFYING FACTORS
RUTHENIUM COMPOUNDS
TRACER TECHNIQUES
TRANSITION ELEMENT COMPOUNDS
UPTAKE