Multiplicity of Leucine Transport Systems in
            <i>Escherichia coli</i>
            K-12

Rahmanian, Mohamad; Claus, David R.; Oxender, Dale L.

doi:10.1128/jb.116.3.1258-1266.1973

Cited by 113 publications

(96 citation statements)

References 18 publications

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Section: Isolation Of Mutants In the Branched-chain Amino Acid Uptakementioning

confidence: 99%

“…D-leucine were mutants with elevated levels of branched-chain amino acid transport (6). The mutant allele livR results in failure of L-leucine to repress the osmotic shock-sensitive high-affinity LIV-I and leucine-specific transport systems and their respective binding proteins, but has no apparent effect on the membrane-bound low-affinity LIV-I1 system (6,10). The lsrR allele, However, results primarily in a derepression of the leucine-specific transport system and in the level of leucine-specific binding protein, with an apparent twofold increase in the LIV-I1 system as well (10 and unpublished experiments).…”

Section: Isolation Of Mutants In the Branched-chain Amino Acid Uptakementioning

confidence: 99%

“…activity is highly regulated and responds t o the level of leucine in the growth medium (6). There is a direct relationship between the level of high-affinity leucine transport and the Repression by leucine.…”

Section: Regulation Of Leucine Transportmentioning

confidence: 99%

“…The leucine-specific system comprises about 20% of the high-affinity transport capacity for leucine of wild-type E. coli K-12. The regulation of the high-affinity transport systems which respond to the level of leucine in the medium has been extensively studied in our laboratory (6)(7)(8)(9)(10). Mutations resulting in a loss of leucine repression have been mapped and characterized (6,10).…”

mentioning

confidence: 99%

“…The regulation of the high-affinity transport systems which respond to the level of leucine in the medium has been extensively studied in our laboratory (6)(7)(8)(9)(10). Mutations resulting in a loss of leucine repression have been mapped and characterized (6,10). The mutations livR (signifying a derepression of the LIV-I and leucine-specific systems) and IstR (signifying derepression of the leucine-specific system and the LIV-I1 systems) determine negatively acting regulatory elements and are genetically closely linked.…”

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confidence: 99%

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Leucine binding protein and regulation of transport in E. coli

et al. 1977

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Leucine is transported into E. coli cells by high‐affinity transport systems (LIV‐I and leucine‐specific systems) which are sensitive to osmotic shock and require periplasmic binding proteins. In addition leucine is transported by a low‐affinity system (LIV‐II) which is membrane bound and retained in membrane vesicle preparations. The LIV‐I system serves for threonine and alanine in addition to the 3 branched‐chain amino acids. The LIV‐II system is more specific for leucine, isoleucine, and valine while the high‐affinity leucine‐specific system has the greatest specificity. A regulatory locus, livR at minute 22 on the E. coli chromosome produces negatively regulated leucine transport and synthesis of the binding proteins. Valine‐resistant strains have been selected to screen for transport mutants. High‐affinity leucine transport mutants that have been identified include a LIV‐binding protein mutant, livJ, a leucine‐specific binding protein mutant livK and a nonbinding protein component of the LIV‐I system, livH. A fourth mutant, livP, appears to be required only for the low‐affinity LIV‐II system. The existence of this latter mutant indicates that LIV‐I and LIV‐II are parallel transport systems. The 4 mutations concerned with high‐affinity leucine transport form a closely linked cluster of genes on the E. coli chromosome at minute 74. The results of recent studies on the regulation of the high‐affinity transport systems suggests that an attenuator site may be operative in its regulation. This complex regulation appears to require a modified leucyl‐tRNA along with the transcription termination factor rho. Regulation of leucine transport is also defective in relaxed strains. Among the branched‐chain amino acids only leucine produces regulatory changes in LIV‐I activity suggesting a special role of this amino acid in the physiology of E. coli. It was shown that the rapid exchange of external leucine for intracellular isoleucine via the LIV‐I system could create an isolucine pseudoauxotrophy and account for the leucine sensitivity of E. coli.

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Section: Isolation Of Mutants In the Branched-chain Amino Acid Uptakementioning

confidence: 99%

Section: Isolation Of Mutants In the Branched-chain Amino Acid Uptakementioning

confidence: 99%

Section: Regulation Of Leucine Transportmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Leucine binding protein and regulation of transport in E. coli

et al. 1977

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Prediction of effects of amino acid supplementation on growth of E. coli B/r

Shu

Shuler

1991

Biotech & Bioengineering

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A mathematical model for the growth of a single cell of E. coli on medium containing amino acid is presented. A mixture of purified amino acids (glutamate, aspartate, serine, tyrosine, and leucine) combined in the ratios found in a natural digest (casein) were employed as the nitrogen source. Each of these amino acids is the representative of a different family of amino acids. The transport mechanisms and assimilation routes for each amino acid were inserted into the prototype model. The enzyme activities and saturation constants used in the model were based on literature data. The maximum velocities for uptake systems were calculated from experimental data. The formation and homeostasis of amino acid pools were regulated through cross-control of the activities of biosynthetic enzymes and of membrane transport of exogenous nutrients. The size of each amino acid pool was determined with mass balance equations that included terms for a transport system, a biosynthesis system, a transaminase enzyme system for interchange between the amino acid families, and a consumption system. The predictions of the extended model with regard to nutrient concentrations and growth rates compared well with the experimental data.

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The leucine binding proteins of Escherichia coli as models for studying the relationships between protein structure and function

Antonucci

Landick

Oxender

1985

J of Cellular Biochemistry

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The genes encoding the leucine binding proteins in E coli have been cloned and their DNA sequences have been determined. One of the binding proteins (LIV-BP) binds leucine, isoleucine, valine, threonine, and alanine, whereas the other (LS-BP) binds only the D- and L-isomers of leucine. These proteins bind their solutes as they enter the periplasm, then interact with three membrane components, livH, livG, and livM, to achieve the translocation of the solute across the bacterial cell membrane. Another feature of the binding proteins is that they must be secreted into the periplasmic space where they carry out their function. The amino acid sequence of the two binding proteins is 80% homologous, indicating that they are the products of an ancestral gene duplication. Because of these characteristics of the leucine binding proteins, we are using them as models for studying the relationships between protein structure and function.

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Multiplicity of Leucine Transport Systems in Escherichia coli K-12

Cited by 113 publications

References 18 publications

Leucine binding protein and regulation of transport in E. coli

Leucine binding protein and regulation of transport in E. coli

Prediction of effects of amino acid supplementation on growth of E. coli B/r

The leucine binding proteins of Escherichia coli as models for studying the relationships between protein structure and function

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