Calcium transport in sealed vesicles from red beet (Beta vulgaris L. ) storage tissue. II. Characterization of /sup 45/Ca/sup 2 +/ uptake into plasma membrane vesicles
Calcium uptake was examined in sealed plasma membrane vesicles isolated from red beet (Beta vulgaris L.) storage tissue using /sup 45/Ca/sup 2 +/. Uptake of /sup 45/Ca/sup 2 +/ by the vesicles was ATP-dependent and radiotracer accumulated by the vesicles could be released by the addition of the calcium ionophore A23187. The uptake was stimulated by gramicidin D but slightly inhibited by carbonylcyanide m-chlorophenylhydrazone. Although the latter result might suggest some degree of indirect coupling of /sup 45/Ca/sup 2 +/ uptake to ATP utilization via ..delta mu..H/sup +/, no evidence for a secondary H/sup +//Ca/sup 2 +/ antiport in this vesicle system could be found. Following the imposition of an acid-interior pH gradient, proton efflux from the vesicle was not enhanced by the addition of Ca/sup 2 +/ and an imposed pH gradient could not drive /sup 45/Ca/sup 2 +/ uptake. Optimal uptake of /sup 45/Ca/sup 2 +/ occurred broadly between pH 7.0 and 7.5 and the transport was inhibited by orthovanadate, N,N'-dicyclohexylcarbodiimide, and diethylstilbestrol but insensitive to nitrate and azide. The dependence of /sup 45/Ca/sup 2 +/ uptake on both calcium and Mg:ATP concentration demonstrated saturation kinetics with K/sub m/ values of 6 micromolar and 0.37 millimolar, respectively. While ATP was the preferred substrate for driving /sup 45/Ca/sup 2 +/ uptake, GTP could drive transport at about 50% of the level observed for ATP. The results of this study demonstrate the presence of a unique primary calcium transport system associated with the plasma membrane which could drive calcium efflux from the plant cell.
- Research Organization:
- Univ. of Illinois, Urbana
- OSTI ID:
- 5640443
- Journal Information:
- Plant Physiol.; (United States), Vol. 85:4
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CALCIUM
MEMBRANE TRANSPORT
ATP
BEETS
CALCIUM 45
CELL MEMBRANES
ENERGY TRANSFER
INHIBITION
ION EXCHANGE
PLANT TISSUES
PROTONS
RESPONSE MODIFYING FACTORS
TRACER TECHNIQUES
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METALS
BARYONS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BODY
CALCIUM ISOTOPES
CELL CONSTITUENTS
DAYS LIVING RADIOISOTOPES
ELEMENTARY PARTICLES
ELEMENTS
EVEN-ODD NUCLEI
FERMIONS
FOOD
HADRONS
INTERMEDIATE MASS NUCLEI
ISOTOPE APPLICATIONS
ISOTOPES
MEMBRANES
METALS
NUCLEI
NUCLEONS
NUCLEOTIDES
ORGANIC COMPOUNDS
PLANTS
RADIOISOTOPES
TISSUES
VEGETABLES
550201* - Biochemistry- Tracer Techniques