Related Experiment Video
Updated: Aug 8, 2026

Profiling Thiol Redox Proteome Using Isotope Tagging Mass Spectrometry
Published on: March 24, 2012
Pyrroline-5-Carboxylate Reductase Is in Pea (Pisum sativum L.) Leaf Chloroplasts
P J Rayapati1, C R Stewart, E Hack
1Department of Botany, Iowa State University, Ames, Iowa 50011.
Abstract:
Proline accumulation is a well-known response to water deficits in leaves. The primary cause of accumulation is proline synthesis. Delta(1)-Pyrroline-5-carboxylate reductase (PCR) catalyzes the final reaction of proline synthesis. To determine the subcellular location of PCR, protoplasts were made from leaves of Pisum sativum L., lysed, and fractionated by differential and Percoll density gradient centrifugation. PCR activity comigrated on the gradient with the activity of the chloroplast stromal marker NADPH-dependent triose phosphate dehydrogenase. We conclude that PCR is located in chloroplasts, and therefore that chloroplasts can synthesize proline. PCR activities from chloroplasts and etiolated shoots were compared. PCR activity from both extracts is stimulated at least twofold by 100 millimolar KCl or 10 millimolar MgCl(2). The pH profiles of PCR activity from both extracts reveal two separate optima at pH 6.5 and 7.5. Native isoelectric focusing gels of sampies from etiolated tissue reveal a single band of PCR activity with a pl of 7.8.
Related Concept Videos
The Calvin Benson Cycle
The Z-Scheme of Electron Transport in Photosynthesis
The Photochemical Reaction Center
Cell Signaling in Plants
Photosystem I
Both these photosystems work in concert. An excited electron from PSII is relayed to PSI via an electron transport chain in the thylakoid membrane of the chloroplast, which is comprised of the carrier molecule plastoquinone, the dual-protein cytochrome complex, and plastocyanin. As electrons move between PSII and PSI, they lose energy and must be re-energized...
Sulfur Assimilation
