Purification of the Chlorella HUP1 hexose-proton symporter to homogeneity and its reconstitution in vitro
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DOI
A prokaryotic biotin acceptor domain was fused to the carboxy terminal end of the Chlorella hexose-proton symporter. The plant symporter is biotinylated in vivo when expressed in Schizosaccharomyces pombe. The extended biotinylated transport protein is fully active, catalyzes accumulation of D-glucose analogs and restores growth of a glucose-uptake-deficient yeast strain. Crude membranes were solubilized with octyl-beta-D-glucoside in the presence of Escherichia coli L-alpha-phosphatidylethanolamine. Biotinylated symporter was purified to homogeneity by biotinavidin affinity chromatography. The symporter protein was reconstituted together with cytochrome-c oxidase prepared from beef heart mitochondria into proteo-liposomes. Cytochrome-c oxidase is a redox-driven H(+)-pump generating a proton motive force (inside negative and alkaline) while transferring electrons from cytochrome-c to oxygen; this energy is used by the symporter to accumulate D-glucose at least 30-fold. In the absence of the driving force the transport protein facilitates diffusion of D-glucose until the concentration equilibrium is reached. It was shown that maximal transport activity depends highly on the amount of co-reconstituted cytochrome-c oxidase and that the symporter possesses 10% of its in vivo turnover number under optimized in vitro transport conditions.
Keywords
- Amino Acid Sequence, Biological Transport, Biotin, Carrier Proteins, Chlorella, Electron Transport Complex IV, Glucose, Membrane Proteins, Molecular Sequence Data, Monosaccharide Transport Proteins, Plant Proteins, Proteolipids, Proton Pumps, Proton-Motive Force, Recombinant Fusion Proteins, Schizosaccharomyces, Solubility, Symporters, Journal Article, Research Support, Non-U.S. Gov't
Original language | English |
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Pages (from-to) | 1045-53 |
Number of pages | 9 |
Journal | Plant Journal |
Volume | 10 |
Issue number | 6 |
DOIs | |
Publication status | Published - Dec 1996 |