Bacterial anion exchange: reductionist and integrative approaches to membrane biology.
Studies of two different bacterial anion exchange proteins (antiporters) led us to conclude that both reductionist and integrative approaches contribute to progress in understanding membrane biology. We have used a reductionist perspective in applying cysteine scanning mutagenesis to probe individual amino acid positions of UhpT (uptake of hexose phosphate transporter), the carrier responsible for transport of glucose 6-phosphate by Escherichia coli. This work has established experimental criteria that should allow one to identify and localize the translocation pathway in such membrane proteins. An integrative view is exemplified by work with OxlT (oxalate transporter), the carrier used by an anaerobe Oxalobacter formigenes to catalyze the antiport of divalent oxalate and monovalent formate. The activity of OxlT is functionally coordinated with that of a cytosolic oxalyl decarboxylase; together, these vectorial and scalar activities constitute a metabolic proton pump, allowing O. formigenes to display decarboxylative phosphorylation. The role played by OxlT argues that membrane carriers can assume unanticipated emergent properties when their biochemical functions are properly articulated in relation to other aspects of cell function.
Maloney
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PC
Department of Physiology, Johns Hopkins University Medical School, Baltimore, MD 21205.
Yan
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Abe
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D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism*; D002462:Cell Membrane / Q000502:physiology* / Q000648:ultrastructure; D004926:Escherichia coli / Q000502:physiology*; D029968:Escherichia coli Proteins; D006089:Gram-Negative Anaerobic Bacteria / Q000502:physiology*; D008954:Models, Biological; D008961:Models, Structural; D009004:Monosaccharide Transport Proteins; D017433:Protein Structure, Secondary; D013403:Sugar Phosphates / Q000378:metabolism
D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D009004:Monosaccharide Transport Proteins; D013403:Sugar Phosphates; C063498:UhpT protein, E coli