Variable effects of nitrate on ATP-dependent proton transport by barley root membranes. [Hordeum vulgare]

Journal Article · Mon Jun 01 04:00:00 EDT 1987 · Plant Physiol.; (United States)

OSTI ID:6066385

DuPont, F M

The effects of NO/sub 3//sup -/ and assay temperature on proton translocating ATPases in membranes of barley (Hordeum vulgare L. cv California Mariout 72) roots were examined. The membranes were fractionated on continuous and discontinuous sucrose gradients and proton transport was assayed by monitoring the fluorescence of acridine orange. A peak of H/sup +/-ATPase at 1.11 grams per cubic centimeter was inhibited by 50 millimolar KNO/sub 3/ when assayed at 24/sup 0/C or above and was tentatively identified as the tonoplast H/sup +/-ATPase. A smaller peak of H/sup +/-ATPase at 1.16 grams per cubic centimeter, which was not inhibited by KNO/sub 3/ and was partially inhibited by vanadate, was tentatively identified as the plasma membrane H/sup +/-ATPase. A step gradient gave three fractions enriched, respectively, in endoplasmic reticulum, tonoplast ATPase, and plasma membrane ATPase. There was a delay before 50 millimolar KNO/sub 3/ inhibited ATP hydrolysis by the tonoplast ATPase at 12/sup 0/C and the initial rate of proton transport was stimulated by 50 millimolar KNO/sub 3/. The time course for fluorescence quench indicated that addition of ATP in the presence of KNO/sub 3/ caused a pH gradient to form that subsequently collapsed. This biphasic time course for proton transport in the presence of KNO/sub 3/ was explained by the temperature-dependent delay of the inhibition by KNO/sub 3/. The plasma membrane H/sup +/-ATPase maintained a pH gradient in the presence of KNO/sub 3/ for up to 30 minutes at 24/sup 0/C.

• Research Organization: Dept. of Agriculture, Albany, CA
• OSTI ID: 6066385
• Journal Information: Plant Physiol.; (United States), Journal Name: Plant Physiol.; (United States) Vol. 84:2; ISSN PLPHA
• Country of Publication: United States
• Language: English

Related Subjects

551000* -- Physiological Systems
59 BASIC BIOLOGICAL SCIENCES
ACID ANHYDRASES
ALKALI METAL COMPOUNDS
ATP-ASE
BARLEY
CARBOHYDRATES
CEREALS
CHARGED-PARTICLE TRANSPORT
DISACCHARIDES
EMISSION SPECTROSCOPY
ENZYME ACTIVITY
ENZYME INHIBITORS
ENZYMES
FLUORESCENCE SPECTROSCOPY
FRACTIONATION
GRASS
HYDROLASES
MEMBRANES
NITRATES
NITROGEN COMPOUNDS
OLIGOSACCHARIDES
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
PH VALUE
PHOSPHOHYDROLASES
PHYSIOLOGY
PLANTS
POTASSIUM COMPOUNDS
POTASSIUM NITRATES
PROTON TRANSPORT
RADIATION TRANSPORT
ROOTS
SACCHARIDES
SACCHAROSE
SEPARATION PROCESSES
SPECTROSCOPY
TEMPERATURE EFFECTS