Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

2-Deoxy-D-galactose, a substrate for the galactose-transport system of Escherichia coli.

ABSTRACT: The following observations showed that 2-deoxy-D-galactose is a useful tool for the isolation and elucidation of the activity of one system for galactose uptake into Escherichia coli. 1. 2-Deoxygalactose, which is not a substrate for growth of E. coli, was transported into strains of the organism induced for galactose transport. 2. By using appropriate mutants it was shown that 2-deoxygalactose is a much better substrate for the galactose-transport system than for the methyl galactoside-transport system. This was confirmed by the results of mutual inhibition studies with substrates of each transport system. 3. The glucose-, arabinose- or lactose-transport systems did not effect significant transport of 2-deoxygalactose. 4. Like other substrates of the galactose-transport system, 2-deoxygalactose promoted effective proton uptake into de-energized suspensions of appropriate E. coli strains. 5. The S183 series of E. coli mutants were found to contain a constitutive galactose-transport system, if 2-deoxygalactose transport is used as one criterion for such activity.

SUBMITTER: Henderson PJ

PROVIDER: S-EPMC1184112 | biostudies-other | 1977 Oct

REPOSITORIES: biostudies-other

ACCESS DATA

Json Xml

Similar Datasets

Structural basis for substrate specificity in the Escherichia coli maltose transport system.

Project description:ATP-binding cassette (ABC) transporters are molecular pumps that harness the chemical energy of ATP hydrolysis to translocate solutes across the membrane. The substrates transported by different ABC transporters are diverse, ranging from small ions to large proteins. Although crystal structures of several ABC transporters are available, a structural basis for substrate recognition is still lacking. For the Escherichia coli maltose transport system, the selectivity of sugar binding to maltose-binding protein (MBP), the periplasmic binding protein, does not fully account for the selectivity of sugar transport. To obtain a molecular understanding of this observation, we determined the crystal structures of the transporter complex MBP-MalFGK2 bound with large malto-oligosaccharide in two different conformational states. In the pretranslocation structure, we found that the transmembrane subunit MalG forms two hydrogen bonds with malto-oligosaccharide at the reducing end. In the outward-facing conformation, the transmembrane subunit MalF binds three glucosyl units from the nonreducing end of the sugar. These structural features explain why modified malto-oligosaccharides are not transported by MalFGK2 despite their high binding affinity to MBP. They also show that in the transport cycle, substrate is channeled from MBP into the transmembrane pathway with a polarity such that both MBP and MalFGK2 contribute to the overall substrate selectivity of the system.

| S-EPMC3831462 | biostudies-literature

Timing of gene transcription in the galactose utilization system of Escherichia coli.

Project description:In the natural environment, bacterial cells have to adjust their metabolism to alterations in the availability of food sources. The order and timing of gene expression are crucial in these situations to produce an appropriate response. We used the galactose regulation in Escherichia coli as a model system for understanding how cells integrate information about food availability and cAMP levels to adjust the timing and intensity of gene expression. We simulated the feast-famine cycle of bacterial growth by diluting stationary phase cells in fresh medium containing galactose as the sole carbon source. We followed the activities of six promoters of the galactose system as cells grew on and ran out of galactose. We found that the cell responds to a decreasing external galactose level by increasing the internal galactose level, which is achieved by limiting galactose metabolism and increasing the expression of transporters. We show that the cell alters gene expression based primarily on the current state of the cell and not on monitoring the level of extracellular galactose in real time. Some decisions have longer term effects; therefore, the current state does subtly encode the history of food availability. In summary, our measurements of timing of gene expression in the galactose system suggest that the system has evolved to respond to environments where future galactose levels are unpredictable rather than regular feast and famine cycles.

| S-EPMC2992240 | biostudies-literature

Proton uptake linked to the 3-deoxy-2-oxo-d-gluconate-transport system of Escherichia coli.

Project description:Genetic and kinetic evidence is presented to show that the carrier-mediated uptake of the anionic sugars 3-deoxy-2-oxo-D-gluconate and D-glucuronate by Escherichia coli involves the concomitant transport of protons.

| S-EPMC1164581 | biostudies-other

Uncoupling substrate transport from ATP hydrolysis in the Escherichia coli maltose transporter.

Project description:Members of the ATP-binding cassette superfamily couple the energy from ATP hydrolysis to the active transport of substrates across the membrane. The maltose transporter, a well characterized model system, consists of a periplasmic maltose-binding protein (MBP) and a multisubunit membrane transporter, MalFGK(2). On the basis of the structure of the MBP-MalFGK(2) complex in an outward-facing conformation (Oldham, M. L., Khare, D., Quiocho, F. A., Davidson, A. L., and Chen, J. (2007) Nature 450, 515-521), we identified two mutants in transmembrane domains MalF and MalG that generated futile cycling; although interaction with MBP stimulated the ATPase activity of the transporter, maltose was not transported. Both mutants appeared to disrupt the normal transfer of maltose from MBP to MalFGK(2). In the first case, substitution of aspartate for glycine in the maltose-binding site of MalF likely generated a futile cycle by preventing maltose from binding to MalFGK(2) during the catalytic cycle. In the second case, a four-residue deletion of a periplasmic loop of MalG limited its reach into the maltose-binding pocket of MBP, allowing maltose to remain associated with MBP during the catalytic cycle. Retention of maltose in the MBP binding site in the deletion mutant, as well as insertion of this loop into the binding site in the wild type, was detected by EPR as a change in mobility of a nitroxide spin label positioned near the maltose-binding pocket of MBP.

| S-EPMC3000980 | biostudies-literature

The gusBC genes of Escherichia coli encode a glucuronide transport system.

Project description:Two genes, gusB and gusC, from a natural fecal isolate of Escherichia coli are shown to encode proteins responsible for transport of beta-glucuronides with synthetic [(14)C]phenyl-1-thio-beta-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 beta-d-glucuronides. Measurements of transport in right-side-out subcellular vesicles show the system has the characteristics of secondary active transport energized by the respiration-generated 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.

| S-EPMC1065211 | biostudies-literature

Transport of galactose, glucose and their molecular analogues by Escherichia coli K12.

Project description:1. Strains of Escherichia coli K12 were made that are unable to assimilate glucose by the phosphotransferase system, since they lack the glucose-specific components specified by the genes ptsG and ptsM. 2. Derivative organisms lacking the methyl galactoside or galactose-specific transport system were examined for their ability to transport galactose, d-fucose, methyl beta-D-galactoside, glucose, 2-deoxy-D-glucose and methyl alpha-D-glucoside. 3. Galactose, glucose and to a lesser extent fucose are substrates for both transport systems. 4. 2-Deoxyglucose is transported on the galactose-specific but not the methyl galactoside system. 5. The ability of sugars to elicit anaerobic proton transport is associated with the galactose-specific, but not with the methyl galactoside transport activity. Hence a chemiosmotic mechanism of energization is likely to apply to the former but not to the latter. Alternatively the methyl galactoside system may be switched off under certain conditions, which would indicate a novel regulatory mechanism. 6. Details of the procedure for the derivation of strains may be obtained from the authors, and have been deposited as Supplementary Publication SUP 50074 (8 pages at the) British Library Lending Division, Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1977), 161,1.

| S-EPMC1164603 | biostudies-other

Energization of the transport systems for arabinose and comparison with galactose transport in Escherichia coli.

Project description:1. Strains of Escherichia coli were obtained containing either the AraE or the AraF transport system for arabinose. AraE+,AraF- strains effected energized accumulation and displayed an arabinose-evoked alkaline pH change indicative of arabinose-H+ symport. In contrast, AraE-,AraF+ strains accumulated arabinose but did not display H+ symport. 2. The ability of different sugars and their derivatives to elicit sugar-H+ symport in AraE+ strains was examined. Only L-arabinose and D-fucose were good substrates, and arabinose was the only inducer. 3. Membrane vesicles prepared from an AraE+,AraF+ strain accumulated the sugar, energized most efficiently by the respiratory substrates ascorbate + phenazine methosulphate. Addition of arabinose or fucose to an anaerobic suspension of membrane vesicles caused an alkaline pH change indicative or sugar-H+ symport on the membrane-bound transport system. 4. Kinetic studies and the effects of arsenate and uncoupling agents in intact cells and membrane vesicles gave further evidence that AraE is a low-affinity membrane-bound sugar-H+ symport system and that AraF is a binding-protein-dependent high-affinity system that does not require a transmembrane protonmotive force for energization. 5. The interpretation of these results is that arabinose transport into E. coli is energized by an electrochemical gradient of protons (AraE system) or by phosphate bond energy (AraF system). 6. In batch cultures the rates of growth and carbon cell yields on arabinose were lower in AraE-,AraF+ strains than in AraE+,AraF- or AraE+,AraF+ strains. The AraF system was more susceptible to catabolite repression than was the AraE system. 7. The properties of the two transport systems for arabinose are compared with those of the genetically and biochemically distinct transport systems for galactose, GalP and MglP. It appears that AraE is analogous to GalP, and AraF to MglP.

| S-EPMC1163584 | biostudies-other

Substrate-triggered position switching of TatA and TatB during Tat transport in Escherichia coli.

Project description:The twin-arginine protein transport (Tat) machinery mediates the translocation of folded proteins across the cytoplasmic membrane of prokaryotes and the thylakoid membrane of plant chloroplasts. The Escherichia coli Tat system comprises TatC and two additional sequence-related proteins, TatA and TatB. The active translocase is assembled on demand, with substrate-binding at a TatABC receptor complex triggering recruitment and assembly of multiple additional copies of TatA; however, the molecular interactions mediating translocase assembly are poorly understood. A 'polar cluster' site on TatC transmembrane (TM) helix 5 was previously identified as binding to TatB. Here, we use disulfide cross-linking and molecular modelling to identify a new binding site on TatC TM helix 6, adjacent to the polar cluster site. We demonstrate that TatA and TatB each have the capacity to bind at both TatC sites, however in vivo this is regulated according to the activation state of the complex. In the resting-state system, TatB binds the polar cluster site, with TatA occupying the TM helix 6 site. However when the system is activated by overproduction of a substrate, TatA and TatB switch binding sites. We propose that this substrate-triggered positional exchange is a key step in the assembly of an active Tat translocase.

| S-EPMC5577447 | biostudies-literature

Galactose repressor mediated intersegmental chromosomal connections in Escherichia coli.

Project description:By microscopic analysis of fluorescent-labeled GalR, a regulon-specific transcription factor in Escherichia coli, we observed that GalR is present in the cell as aggregates (one to three fluorescent foci per cell) in nongrowing cells. To investigate whether these foci represent GalR-mediated association of some of the GalR specific DNA binding sites (gal operators), we used the chromosome conformation capture (3C) method in vivo. Our 3C data demonstrate that, in stationary phase cells, many of the operators distributed around the chromosome are interacted. By the use of atomic force microscopy, we showed that the observed remote chromosomal interconnections occur by direct interactions between DNA-bound GalR not involving any other factors. Mini plasmid DNA circles with three or five operators positioned at defined loci showed GalR-dependent loops of expected sizes of the intervening DNA segments. Our findings provide unique evidence that a transcription factor participates in organizing the chromosome in a three-dimensional structure. We believe that these chromosomal connections increase local concentration of GalR for coordinating the regulation of widely separated target genes, and organize the chromosome structure in space, thereby likely contributing to chromosome compaction.

| S-EPMC3396475 | biostudies-literature

Trypanosoma brucei UDP-galactose-4'-epimerase in ternary complex with NAD+ and the substrate analogue UDP-4-deoxy-4-fluoro-alpha-D-galactose.

Project description:The structure of the NAD-dependent oxidoreductase UDP-galactose-4'-epimerase from Trypanosoma brucei in complex with cofactor and the substrate analogue UDP-4-deoxy-4-fluoro-alpha-D-galactose has been determined using diffraction data to 2.7 A resolution. Despite the high level of sequence and structure conservation between the trypanosomatid enzyme and those from humans, yeast and bacteria, the binding of the 4-fluoro-alpha-D-galactose moiety is distinct from previously reported structures. Of particular note is the observation that when bound to the T. brucei enzyme, the galactose moiety of this fluoro-derivative is rotated approximately 180 degrees with respect to the orientation of the hexose component of UDP-glucose when in complex with the human enzyme. The architecture of the catalytic centre is designed to effectively bind different orientations of the hexose, a finding that is consistent with a mechanism that requires the sugar to maintain a degree of flexibility within the active site.

| S-EPMC2242870 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data