Further characterization of the red beet plasma membrane Ca sup 2+ -ATPase using GTP as an alternative substrate

Journal Article · Thu Mar 01 04:00:00 EST 1990 · Plant Physiology; (USA)

DOI:https://doi.org/10.1104/pp.92.3.747· OSTI ID:5858097

Williams, L E; Schueler, S B; Briskin, D P ^[1]

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1. Univ. of Illinois, Urbana (USA)

The GTP-driven component of Ca{sup 2+} uptake in red beet (Beta vulgaris L.) plasma membrane vesicles was further characterized to confirm its association with the plasma membrane Ca{sup 2+}-translocating ATPase and assess its utility as a probe for this transport system. Uptake of {sup 45}Ca{sup 2+} in the presence of GTP demonstrated similar properties to those previously observed for red beet plasma membrane vesicles utilizing ATP with respect to pH optimum sensitivity to orthovanadate, dependence on Mg:substrate concentration and dependence on Ca{sup 2+} concentration. Calcium uptake in the presence of GTP was also strongly inhibited by erythrosin B, a potent inhibitor of the plant plasma membrane Ca{sup 2+}-ATPase. Furthermore, after treatment with EGTA to remove endogenous calmodulin, the stimulation of {sup 45}Ca{sup 2+}-uptake by exogeneous calmodulin was nearly equivalent in the presence of either ATP or GTP. Taken together these results support the proposal that GTP-driven {sup 45}Ca{sup 2+} uptake represents the capacity of the plasma membrane Ca{sup 2+}-translocating ATPase to utilize this nucleoside triphosphate as an alternative substrate. When plasma membrane vesicles were phosphorylated with ({gamma}-{sup 32}P)GTP, a rapidly turning over, 100 kilodalton phosphorylated peptide was observed which contained an acyl-phosphate linkage. While it is proposed that this peptide could represent the catalytic subunit of the plasma membrane Ca{sup 2+}-ATPase, it is noted that this molecular weight is considerably lower than the 140 kilodalton size generally observed for plasma membrane Ca{sup 2+}-ATPases present in animal cells.

• OSTI ID: 5858097
• Journal Information: Plant Physiology; (USA), Journal Name: Plant Physiology; (USA) Vol. 92:3; ISSN 0032-0889; ISSN PLPHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ACID ANHYDRASES
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METAL COMPOUNDS
ALKALINE EARTH METALS
ATP-ASE
BEETS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CALCIUM
CALCIUM 45
CALCIUM COMPOUNDS
CALCIUM ISOTOPES
CELL CONSTITUENTS
CELL MEMBRANES
DAYS LIVING RADIOISOTOPES
ELEMENTS
ENDOPLASMIC RETICULUM
ENZYMES
EVEN-ODD NUCLEI
FOOD
HYDROLASES
INTERMEDIATE MASS NUCLEI
ISOTOPE APPLICATIONS
ISOTOPES
MAGNOLIOPHYTA
MAGNOLIOPSIDA
MEMBRANES
METABOLISM
METALS
NUCLEI
ORGANOIDS
PHOSPHOHYDROLASES
PLANTS
RADIOISOTOPES
TRACER TECHNIQUES
UPTAKE
VEGETABLES