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M G Borbolla

Publications and source records attributed to M G Borbolla.

4 recordsLinked to original sources
PubMed1984

A plasmid-encoded arsenite pump produces arsenite resistance in Escherichia coli.

The arsenate resistance operon of R-factor R773, a conjugative resistance plasmid, has two functional regions, a promoter-proximal region encoding resistance to arsenite and antimonate, and a promoter-distal one encoding arsenate resistance. Cells bearing arsenite resistance plasmids exhibited reduced accumulation of 74AsO2-. When resistant cells were depleted of endogenous energy reserves and then loaded with 74AsO2-, active extrusion of the ion was observed when an energy source was supplied. Intracellular ATP was required for extrusion, but a proton motive force was neither necessary nor sufficient. An arsenite-sensitive mutant was unable to extrude arsenite, while an arsenate-sensitive mutant had normal arsenite transport. These results suggest that the action of a plasmid-encoded primary arsenite efflux pump is the mechanism of arsenite resistance.

Adenosine Triphosphate↗
PubMed1984

Energetics of sodium efflux from Escherichia coli.

When energy-starved cells of Escherichia coli were passively loaded with 22Na+, efflux of sodium could be initiated by addition of a source of metabolic energy. Conditions were established where the source of energy was phosphate bond energy, an electrochemical proton gradient, or both. Only an electrochemical proton gradient was required for efflux from intact cells. These results are consistent with secondary exchange of Na+ for H+ catalyzed by a sodium/proton antiporter.

Biological Transport, Active↗