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Copper transport across pea thylakoid membranes
Richard Shingles1, Larry E Wimmers, Richard E McCarty
1Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218-2685, USA. shingles@jhu.edu
Plant Physiology
|May 4, 2004
Summary
Copper ion (Cu2+) transport across pea chloroplast thylakoid membranes is rapid, occurring within 0.5 seconds. Results suggest multiple transporters may be involved, as zinc ions (Zn2+) partially inhibit Cu2+ uptake.
Area of Science:
- Plant Physiology
- Biochemistry
- Photosynthesis Research
Background:
- Thylakoid membranes are crucial for photosynthesis in chloroplasts.
- Understanding ion transport is key to chloroplast function and plant health.
- Copper (Cu2+) plays vital roles but its membrane transport is not fully understood.
Purpose of the Study:
- To directly measure the initial rate of Cu2+ movement across pea (Pisum sativum) chloroplast thylakoid membranes.
- To investigate the kinetics and regulatory factors of Cu2+ uptake.
- To explore the potential involvement of multiple transporters for Cu2+.
Main Methods:
- Stopped-flow spectrofluorometry using the Cu2+-sensitive fluorophore Phen Green SK.
- Direct measurement of rapid Cu2+ transport kinetics.
- Analysis of Cu2+ uptake rates under varying Cu2+ concentrations and pH.
Main Results:
- Cu2+ transport across thylakoid membranes was rapid, completing within 0.5 seconds.
- Uptake rate saturated at approximately 0.6 microm total Cu2+ and was maximal at pH 7.0.
- Zinc ions (Zn2+) inhibited Cu2+ transport by up to 60%, while Mn2+ and Cu+ had no significant effect.
Conclusions:
- Pea chloroplast thylakoid membranes exhibit rapid Cu2+ transport.
- The pH optimum for Cu2+ uptake is 7.0.
- Partial inhibition by Zn2+ suggests the presence of multiple Cu2+ transporters in pea thylakoid membranes.