Nitrite transport in chloroplast inner envelope vesicles. I. Direct measurement of proton-linked transport
- Johns Hopkins Univ., Baltimore, MD (United States)
Chloroplast inner envelope membrane vesicles that are loaded with the pH-sensitive fluorophore, pyranine, show rapid internal acidification when nitrite is added. Acidification is dependent upon {Delta}pH, with the inside of vesicles being alkaline with respect to the outside. The rate of vesicle acidification was directly proportional to the concentration of nitrite that was added and the imposed pH difference across the membrane. In contrast, added nitrate had no effect on vesicle acidification. Nitrite also caused acidification of asolectin vesicles that were prepared by extrusion were approximately the same size, allowing them to be compared when the final extent of acidification, measured after the pH gradient had collapsed, was similar. The rate of nitrite-dependent acidification was similar in these two preparations at any single nitrite concentration. These results indicate that nitrite movement occurs by rapid diffusion across membranes as nitrous acid, and this movement is dependent on a proton gradient across the lipid bilayer. Under conditions approximating these in vivo, the rate of diffusion of nitrous acid far exceeds that of nitrite reduction within chloroplasts. 26 refs., 5 figs., 1 tab.
- OSTI ID:
- 495300
- Journal Information:
- Plant Physiology (Bethesda), Vol. 112, Issue 3; Other Information: PBD: Nov 1996
- Country of Publication:
- United States
- Language:
- English
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