Calcium transport in tonoplast and endoplasmic reticulum vesicles isolated from cultured carrot cells. [Daucus carota Danvers]
Two active calcium (Ca/sup 2 +/) transport systems have been identified and partially characterized in membrane vesicles isolated from cultured carrot cells (Daucus carota Danvers). Both transport systems required MgATP for activity and were enhanced by 10 millimolar oxalate. Ca/sup 2 +/ transport in membrane vesicles derived from isolated vacuoles equilibrated at 1.10 grams per cubic centimeter and comigrated with Cl/sup -/-stimulated, NO/sub 3//sup -/-inhibited ATPase activity on sucrose density gradients. Ca/sup 2 +/ transport in this system was insensitive to vanadate, but was inhibited by nitrate, carbonyl cyanide-m-chlorophenylhydrazone (CCCP), N,N'-dicyclohexylcarbodiimide (DCCD), and 4,4-diisothiocyano-2,2'-stilbene disulfonic acid (DIDS). The K/sub m/ for MgATP and Ca/sup 2 +/ were 0.1 mM and 21 micromolar, respectively. The predominant Ca/sup 2 +/ transport system detectable in microsomal membrane preparations equilibrated at a density of 1.13 grams per cubic centimeter and comigrated with the endoplasmic reticulum (ER) marker, antimycin A-insensitive NADH-dependent cytochrome c reductase. Ca/sup 2 +/ transport activity and the ER marker also shifted in parallel in ER shifting experiments. This transport system was inhibited by vanadate (I/sub 50/ = 12 micromolar) and was insensitive to nitrate, CCCP, DCCD, and DIDS. Transport exhibited cooperative MgATP dependent kinetics. Ca/sup 2 +/ dependent kinetics were complex with an apparent K/sub m/ ranging from 0.7 to 2 micromolar. We conclude that the vacuolar-derived system is a Ca/sup 2 +//H/sup +/ antiport located on the tonoplast and that the microsomal transport system is a Ca,Mg-ATPase enriched on the ER. These two Ca/sup 2 +/ transport systems are proposed to restore and maintain cytoplasmic Ca/sup 2 +/ homeostasis under changing cellular and environmental conditions.
- Research Organization:
- Univ. of Maryland, College Park
- DOE Contract Number:
- AS05-82ER13015
- OSTI ID:
- 5742456
- Journal Information:
- Plant Physiol.; (United States), Vol. 80:2
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CALCIUM
MEMBRANE TRANSPORT
CARROTS
ENDOPLASMIC RETICULUM
CHEMICAL ACTIVATION
INHIBITION
ANIONS
ANTIMYCIN
ATP
ATP-ASE
BIOCHEMICAL REACTION KINETICS
CATIONS
CELL CULTURES
CHLORIDES
CYANIDES
CYTOCHROMES
ENZYME ACTIVITY
EXPERIMENTAL DATA
HOMEOSTASIS
HYDRAZONES
MAGNESIUM
MICROSOMES
NADH2
NITRATES
OXALATES
OXIDOREDUCTASES
PLANT CELLS
SACCHAROSE
SULFONIC ACIDS
VANADATES
ACID ANHYDRASES
ALKALINE EARTH METALS
ANTI-INFECTIVE AGENTS
ANTIBIOTICS
CARBOHYDRATES
CARBOXYLIC ACID SALTS
CELL CONSTITUENTS
CHARGED PARTICLES
CHLORINE COMPOUNDS
COENZYMES
DATA
DISACCHARIDES
DRUGS
ELEMENTS
ENZYMES
FOOD
HALIDES
HALOGEN COMPOUNDS
HYDROLASES
INFORMATION
IONS
KINETICS
METALS
NITROGEN COMPOUNDS
NUCLEOTIDES
NUMERICAL DATA
OLIGOSACCHARIDES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC SULFUR COMPOUNDS
ORGANOIDS
OXYGEN COMPOUNDS
PHOSPHOHYDROLASES
PIGMENTS
PLANTS
PROTEINS
REACTION KINETICS
SACCHARIDES
TRANSITION ELEMENT COMPOUNDS
VANADIUM COMPOUNDS
VEGETABLES
550500* - Metabolism