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Phosphate transport in membrane vesicles from Escherichia coli
Biochimica Et Biophysica Acta
|April 4, 1978
Summary
Escherichia coli strain AN710 utilizes the Phosphate Inorganic Transporter (PIT) system for phosphate transport, energized by its respiratory chain. This process is driven by the proton-motive force, particularly the pH gradient.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Escherichia coli employs various transport systems for essential nutrient uptake.
- Phosphate is a critical nutrient for bacterial growth and metabolic processes.
- Understanding phosphate transport mechanisms is vital for comprehending bacterial physiology.
Purpose of the Study:
- To investigate the characteristics of the Phosphate Inorganic Transporter (PIT) system in Escherichia coli strain AN710.
- To determine the energy sources and driving forces for phosphate transport via the PIT system.
- To compare the functionality of the PIT system with the Phosphate:Solute Symporter (PST) system.
Main Methods:
- Isolation and characterization of membrane vesicles from Escherichia coli strains AN710 (PIT system) and K10 (PST system).
- Assay of phosphate exchange and active transport in membrane vesicles.
- Evaluation of electron donors (ascorbate-phenazine methosulphate, D-lactate, succinate) for energizing transport.
- Assessment of the effect of ionophores (valinomycin, nigericin) and uncouplers (carbonyl cyanide m-chlorophenylhydrazone) on transport.
- Investigation of the impact of phosphate analogue (arsenate) and cations (K+, Mg2+) on transport activity.
Main Results:
- Escherichia coli AN710 membrane vesicles exhibited both phosphate exchange and active transport, mediated by the PIT system.
- Active phosphate transport was primarily energized by the respiratory chain using ascorbate-phenazine methosulphate and, to a lesser extent, D-lactate.
- Phosphate transport was driven by the proton-motive force, specifically the pH gradient, and was sensitive to ionophores and uncouplers.
- Phosphate exchange and active transport were inhibited by arsenate and stimulated by K+ and Mg2+.
- Membrane vesicles from Escherichia coli K10 (PST system) did not show phosphate transport activity.
Conclusions:
- The PIT system in Escherichia coli AN710 is responsible for both phosphate exchange and active transport.
- The proton-motive force, particularly the pH gradient, is the primary driving force for PIT-mediated phosphate transport.
- The PST system in Escherichia coli K10 appears non-functional for phosphate transport under the tested conditions.
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