The association of proton movement with galactose transport into subcellular membrane vesicles of <i>Escherichia coli</i>

Horne, P; Henderson, Peter J. F.

doi:10.1042/bj2100699

Cited by 15 publications

(1 citation statement)

References 35 publications

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“…However, the use of right-side-out vesicles (26,32) enables such a distinction, because the binding proteins and ATP necessary for primary active transport are eliminated.…”

Section: Resultsmentioning

confidence: 99%

ThegusBCGenes ofEscherichia coliEncode a Glucuronide Transport System

et al. 2005

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Two genes, gusB and gusC, from a natural fecal isolate of Escherichia coli are shown to encode proteins responsible for transport of ␤-glucuronides with synthetic [14 C]phenyl-1-thio-␤-D-glucuronide as the substrate. These genes are located in the gus operon downstream of the gusA gene on the E. coli genome, and their expression is induced by a variety of ␤-D-glucuronides. Measurements of transport in right-side-out subcellular vesicles show the system has the characteristics of secondary active transport energized by the respirationgenerated proton motive force. When the genes were cloned together downstream of the tac operator-promoter in the plasmid pTTQ18 expression vector, transport activity was increased considerably with isopropylthiogalactopyranoside as the inducer. Amplified expression of the GusB and GusC proteins enabled visualization and identification by N-terminal sequencing of both proteins, which migrated at ca. 32 kDa and 44 kDa, respectively. Separate expression of the GusB protein showed that it is essential for glucuronide transport and is located in the inner membrane, while the GusC protein does not catalyze transport but assists in an as yet unknown manner and is located in the outer membrane. The output of glucuronides as waste by mammals and uptake for nutrition by gut bacteria or reabsorption by the mammalian host is discussed.

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“…However, the use of right-side-out vesicles (26,32) enables such a distinction, because the binding proteins and ATP necessary for primary active transport are eliminated.…”

Section: Resultsmentioning

confidence: 99%

ThegusBCGenes ofEscherichia coliEncode a Glucuronide Transport System

et al. 2005

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Active Transport of Sugars into Escherichia coli

Henderson

1986

Carbohydrate Metabolism in Cultured Cells

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Proton-linked sugar transport systems in bacteria

Henderson

1990

J Bioenerg Biomembr

156

108

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The cell membranes of various bacteria contain proton-linked transport systems for D-xylose, L-arabinose, D-galactose, D-glucose, L-rhamnose, L-fucose, lactose, and melibiose. The melibiose transporter of E. coli is linked to both Na+ and H+ translocation. The substrate and inhibitor specificities of the monosaccharide transporters are described. By locating, cloning, and sequencing the genes encoding the sugar/H+ transporters in E. coli, the primary sequences of the transport proteins have been deduced. Those for xylose/H+, arabinose/H+, and galactose/H+ transport are homologous to each other. Furthermore, they are just as similar to the primary sequences of the following: glucose transport proteins found in a Cyanobacterium, yeast, alga, rat, mouse, and man; proteins for transport of galactose, lactose, or maltose in species of yeast; and to a developmentally regulated protein of Leishmania for which a function is not yet established. Some of these proteins catalyze facilitated diffusion of the sugar without cation transport. From the alignments of the homologous amino acid sequences, predictions of common structural features can be made: there are likely to be twelve membrane-spanning alpha-helices, possibly in two groups of six; there is a central hydrophilic region, probably comprised largely of alpha-helix; the highly conserved amino acid residues (40-50 out of 472-522 total) form discrete patterns or motifs throughout the proteins that are presumably critical for substrate recognition and the molecular mechanism of transport. Some of these features are found also in other transport proteins for citrate, tetracycline, lactose, or melibiose, the primary sequences of which are not similar to each other or to the homologous series of transporters. The glucose/Na+ transporter of rabbit and man is different in primary sequence to all the other sugar transporters characterized, but it is homologous to the proline/Na+ transporter of E. coli, and there is evidence for its structural similarity to glucose/H+ transporters in Plants. In vivo and in vitro mutagenesis of the lactose/H+ and melibiose/Na+ (H+) transporters of E. coli has identified individual amino acid residues alterations of which affect sugar and/or cation recognition and parameters of transport. Most of the bacterial transport proteins have been identified and the lactose/H+ transporter has been purified. The directions of future investigations are discussed.

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The association of proton movement with galactose transport into subcellular membrane vesicles of Escherichia coli

Cited by 15 publications

References 35 publications

ThegusBCGenes ofEscherichia coliEncode a Glucuronide Transport System

ThegusBCGenes ofEscherichia coliEncode a Glucuronide Transport System

Active Transport of Sugars into Escherichia coli

Proton-linked sugar transport systems in bacteria

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