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H R Kaback

Publications and source records attributed to H R Kaback.

At least 325 records · Page 18Linked to original sources
PubMed1972

Mutants of Salmonella typhimurium and Escherichia coli pleiotropically defective in active transport.

Two classes of mutants isolated from E. coli and Salmonella typhimurium are altered in respiration-coupled active transport, as studied in whole cells and/or isolated membrane vesicles. Mutant cells defective in D-lactate dehydrogenase (dld) transport amino acids and lactose normally. Membrane vesicles prepared from these mutants do not exhibit D-lactate-dependent transport, D-lactate oxidation, or D-lactate: dichlorophenolindophenol reductase activity. However, succinate-dependent transport is markedly enhanced in these mutants, without a corresponding increase in succinic dehydrogenase activity. The second class of mutants is defective in the coupling of electron transfer to active transport. Whole cells and membrane vesicles prepared from these etc mutants exhibit markedly reduced ability to transport amino acids, despite the ability of the vesicles to oxidize D-lactate, succinate, and NADH. Vectorial phosphorylation of alpha-methylglucoside by these mutants is normal. Electrontransfer coupling mutants are similar phenotypically to mutants uncoupled for oxidative phosphorylation (uncA), but have normal ATPase activity. Moreover, uncA mutants catalyze active transport as well as does the wild type. These experiments indicate that the ETC component is essential for the coupling of respiratory energy to active transport, and provide further evidence that the generation or utilization of ATP is not involved in these transport mechanisms.

Adenosine Triphosphatases↗
PubMed1972

Solubilization and partial purification of amino acid-specific components of the D-lactate dehydrogenase-coupled amino acid-transport systems (E. coli-cell membranes-sephadex-detergent-solubilized-vesicles).

A protein-containing fraction has been solubilized from E. coli ML 308-225 membrane vesicles that has many of the properties of the amino acid "carrier proteins" of the D-lactate dehydrogenase-coupled amino acid-transport systems. Membrane vesicles were partially solubilized with the nonionic detergent Brij 36-T, and the solubilized material was fractionated by Sephadex G-100 chromatography in the presence of the same detergent. Three fractions possess binding activity for proline: one of relatively low molecular weight with a high specific activity, and two of higher molecular weight with low specific activities. The higher molecular weight fractions exhibit D-lactate dehydrogenase activity; however, there is no corresponding activity associated with the low molecular weight fraction. Moreover, proline-binding activity is highly specific as it is not inhibited by structurally-unrelated amino acids. In addition to proline, the low molecular weight fraction exhibits binding activities for serine, glycine, lysine, and tyrosine. The proline-binding activity of the low molecular weight fraction is not inhibited by electron transfer or by general metabolic inhibitors that inhibit the accumulation of proline by intact membrane vesicles. In contrast, binding activity is inhibited by p-chloromercuribenzoate and N-ethylmaleimide, and the inhibition observed with p-chloromercuribenzoate is reversed by the addition of dithiothreitol. The effect of these sulfhydryl reagents on binding corresponds to the effect of these compounds on proline transport by intact membrane vesicles.

Bacterial Proteins↗
PubMed1970

The role of phosphatidylglycerol in the vectorial phosphorylation of sugar by isolated bacterial membrane preparations.

Phospholipase D (cabbage) inhibits the vectorial phosphorylation of alpha-methylglucoside by isolated membrane preparations from Escherichia coli ML 308-225 without increasing the efflux of intramembranal alpha-methylglucoside-P. This effect is shown to be related to the ability of phospholipase D to hydrolyze membrane phosphatidylglycerol specifically. After treatment with phospholipase D, the membranes resynthesize phosphatidylglycerol with a return in their ability to take up alpha-methylglucoside. Since proline uptake by the same preparations is only slightly inhibited by phospholipase D, the data indicate that phosphatidylglycerol is required specifically for transport processes which are mediated by the P-enolpyruvate-P-transferase system.

Carbon Isotopes↗
PubMed1970

Relationship of a membrane-bound D-(-)-lactic dehydrogenase to amino acid transport in isolated bacterial membrane preparations.

The conversion of D-lactate to pyruvate in isolated membrane preparations of E. coli ML 308-225 markedly stimulates the transport of proline, glutamic acid, aspartic acid, aspargine, tryptophan, lysine, serine, alanine, and glycine. The uptake of histidine, phenylalanine, tyrosine, leucine, isoleucine, and valine by the membranes is also markedly stimulated by this conversion, although these amino acids are taken up much less effectively than those mentioned previously. The uptake of arginine, methionine, cystine, and cysteine is enhanced only about twofold in the presence of D-(-)-lactate, and these amino acids are not concentrated well by the membranes. With the exception of glutamate, asparate, asparagine, and methionine, which are converted to other metabolites to varying extents in the intramembranal pool, each of the other amino acids was recovered from the membranes as the unchanged amino acid. Succinate, L-(+)-lactate, D,L-alpha-hydroxybutyrate, and DPNH partially replace D-(-)-lactate but are less effective.

Acetates↗
PubMed1970

Beta-galactoside transport in bacterial membrane preparations: energy coupling via membrane-bounded D-lactic dehydrogenase.

The transport of beta-galactosides by isolated membrane preparations from Escherichia coli strains containing a functional y gene is markedly stimulated by the conversion of D-lactate to pyruvate. The addition of D-lactate to these membrane preparations produces a 19-fold increase in the initial rate of uptake and a 10-fold stimulation of the steady-state level of intramembranal lactose or thiomethylgalactoside. Succinate, DL-alpha-hydroxybutyrate, and L-lactate partially replace D-lactate, but are much less effective; ATP and P-enolpyruvate, in addition to a number of other metabolites and cofactors, do not stimulate lactose transport by the vesicles. Lactose uptake by the membrane preparations in the presence of D-lactate requires oxygen, and is blocked by electron transport inhibitors and proton conductors; however, uptake is not significantly inhibited by high concentrations of arsenate or oligomycin. Furthermore, the P-enolpyruvate-P-transferase system is not involved in beta-galactoside transport by the E. coli membrane vesicles. The findings indicate that the beta-galactoside uptake system is coupled to the membrane-bound D-lactic dehydrogenase via an electron transport chain but does not involve oxidative phosphorylation.

Acetates↗
PubMed1970

Transport.

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Adenosine Triphosphatases↗
PubMed1969

Regulation of sugar transport in isolated bacterial membrane preparations from Escherichia coli.

The experiments presented in this paper demonstrate that glucose transport via the phosphoenolpyruvate-phosphotransferase system as studied in isolated E. coli membrane preparations is subject to regulation by sugar-P's. Glucose transport in these preparations is inhibited by glucose-6-P, glucose-1-P, and, to a lesser extent, by other P-esters. There appear to be two inhibitory sites, one specific for glucose-1-P and related sugar-1-P's and the other specific for glucose-6-P and related sugar-6-P's. The inhibition by these sugar-P's is noncompetitive, and the inhibitory sites are separate, subject to independent control, and apparently are accessible from outside the membrane. Furthermore, glucose-6-P is able to reverse partially inhibition of glucose transport by glucose-1-P and vice versa. Preliminary evidence is presented indicating that glucose-1-P may play a central role in the regulation of sugar transport in general, by virtue of its ability to inhibit selectively the transport of sugars other than glucose.

Biological Transport↗