K. Abe et al., CLONING, SEQUENCING, AND EXPRESSION IN ESCHERICHIA-COLI OF OXLT, THE OXALATE, FORMATE EXCHANGE PROTEIN OF OXALOBACTER-FORMIGENES, The Journal of biological chemistry, 271(12), 1996, pp. 6789-6793
OxlT is the oxalate/formate exchange protein that represents the vecto
rial component of a proton-motive metabolic cycle in Oxalobacter formi
genes. Here we report the cloning and sequencing of OxlT and describe
its expression in Escherichia coli. The OxlT amino acid sequence speci
fies a polytopic hydrophobic protein of 418 residues with a mass of 44
,128 daltons. Analysis of hydropathy and consideration of the distribu
tion of charged residues suggests an OxlT secondary structure having 1
2 transmembrane segments, oriented so that the N and C termini face th
e cytoplasm. Expression of OxlT in E. coli coincides with appearance o
f a capacity to carry out the self-exchange of oxalate and the heterol
ogous, electrogenic exchange of oxalate with formate. The unusually hi
gh velocity of OxlT-mediated transport is also preserved in E. coli. W
e conclude that the essential features of OxlT are retained on its exp
ression in E. coli.