Oat tonoplast H/sup +//Ca/sup 2 +/ antiport is a reversible, electrogenic transport system
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
- Journal Information:
- Plant Physiol.; (United States), Vol. 80:4; Conference: Annual meeting of the American Society of Plant Physiologists, Baton Rouge, LA, USA, 8-12 Jun 1986
- Country of Publication:
- United States
- Language:
- English
Similar Records
Decrease of pH gradients in tonoplast vesicles by NO/sub 3//sup -/ and Cl/sup -/: evidence for H/sup +/-coupled anion transport
Calcium transport in tonoplast and endoplasmic reticulum vesicles isolated from cultured carrot cells. [Daucus carota Danvers]
Related Subjects
CALCIUM COMPOUNDS
BIOCHEMICAL REACTION KINETICS
PLANT CELLS
PHYSIOLOGY
ATP
ATP-ASE
CALCIUM 45
CATIONS
CELL MEMBRANES
IMIDES
LABELLED COMPOUNDS
LANTHANUM COMPOUNDS
NITRATES
PH VALUE
RESPONSE MODIFYING FACTORS
RUTHENIUM COMPOUNDS
TRACER TECHNIQUES
UPTAKE
ACID ANHYDRASES
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METAL COMPOUNDS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CALCIUM ISOTOPES
CELL CONSTITUENTS
CHARGED PARTICLES
DAYS LIVING RADIOISOTOPES
ENZYMES
EVEN-ODD NUCLEI
HYDROLASES
INTERMEDIATE MASS NUCLEI
IONS
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
MEMBRANES
NITROGEN COMPOUNDS
NUCLEI
NUCLEOTIDES
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXYGEN COMPOUNDS
PHOSPHOHYDROLASES
RADIOISOTOPES
RARE EARTH COMPOUNDS
REACTION KINETICS
REFRACTORY METAL COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
551001* - Physiological Systems- Tracer Techniques