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The uptake of a sugar across the boundary membrane is a primary event in the nutrition of most cells, but the hydrophobic nature of the transport proteins involved makes them difficult to characterize. Their amino-acid sequences can, however, be determined by cloning and sequencing the corresponding gene (or complementary DNA). We have determined the sequences of the arabinose-H+ and xylose-H+ membrane transport proteins of Escherichia coli. They are homologous with each other and, unexpectedly, with the glucose transporters of human hepatoma and rat brain cells. All four proteins share similarities with the E. coli citrate transporter. Comparisons of their sequences and hydropathic profiles yield insights into their structure, functionally important residues and possible evolutionary relationships. There is little apparent homology with the lactose-H+ (LacY) or melibiose-Na+ (MelB) transport proteins of E. coli.

Original publication

DOI

10.1038/325641a0

Type

Journal article

Journal

Nature

Publication Date

12/02/1987

Volume

325

Pages

641 - 643

Keywords

Amino Acid Sequence, Arabinose, Base Sequence, Carbohydrate Metabolism, Carrier Proteins, Escherichia coli, Glucose, Humans, Lactose, Xylose