Prokaryotic Binding Protein‐Dependent ABC Transporters

Boos, Winfried; Eppler, Tanja

doi:10.1002/3527600728.ch4

Cited by 72 publications

(109 citation statements)

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“…The resulting models have given us a much broader understanding of the ways in which physical events may be man- ifested in the behavior of the experimental system. These studies provide further support for suggestions that both ligand-free and ligand-bound forms of binding protein can interact with the membrane transport complex (Prossnitz et al, 1989;Davidson et al, 1992;Boos & Lucht, 1995). This competition has important consequences for the behavior of the system, allowing it to remain responsive to changes in ligand concentrations over a wide range of binding protein concentrations (a critical feature in a system where the binding protein is inducible and therefore present at fluctuating levels).…”

Section: Discussionmentioning

confidence: 61%

“…A large amount of experimental data is available for the binding protein-dependent transport systems of gram-negative bacteria (for reviews of these systems, see Ames, 1986;Boos & Lucht, 1995), but in the absence of an adequate theoretical framework that can be applied conveniently, it has often been hard to know how to evaluate it. As a result, key measurements have sometimes been lacking, and important conclusions missed or inadequately substantiated.…”

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confidence: 99%

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Simple models for the analysis of binding protein‐dependent transport systems

Shilton

Mowbray

1995

Protein Science

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Mathematical modeling was used to evaluate experimental data for bacterial binding protein-dependent transport systems. Two simple models were considered in which ligand-free periplasmic binding protein interacts with the membrane-bound components of transport. In one, this interaction was viewed as a competition with the ligandbound binding protein, whereas in the other, it was considered to be a consequence of the complexes formed during the transport process itself. Two sets of kinetic parameters were derived for each model that fit the available experimental results for the maltose system. By contrast, a model that omitted the interaction of ligand-free binding protein did not fit the experimental data. Some applications of the successful models for the interpretation of existing mutant data are illustrated, as well as the possibilities of using mutant data to test the original models and sets of kinetic parameters. Practical suggestions are given for further experimental design.

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Section: Discussionmentioning

confidence: 61%

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confidence: 99%

Simple models for the analysis of binding protein‐dependent transport systems

Shilton

Mowbray

1995

Protein Science

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“…The co-ordination offered by this genetic organization is thought to ensure expression of ABC components in fixed stoichiometric ratios that are important for the assembly and function of these transporters (Boos and Lucht, 1996). The kps locus is different from other capsule loci in that the presumed energy-transducing (KpsT) and integral membrane (KpsM) components of the ABC-2 transporter are encoded in region 3, whereas KpsE, which is thought to couple the KpsMT channel to the outer membrane, is encoded in region 1.…”

Section: Discussionmentioning

confidence: 99%

Reduced polysialic acid capsule expression in Escherichia coli K1 mutants with chromosomal defects in kpsF

Cieslewicz

Vimr

1997

Molecular Microbiology

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SummaryNeuroinvasive Escherichia coli K1 synthesizes and assembles a polysialic acid capsule virulence factor on the external leaflet of the outer membrane. This capsule functions in pathogenesis by blocking nonimmune host defence mechanisms and acting as a relatively non-immunogenic molecular mimic of the polysialic acid chains found in high concentrations on neural cell adhesion molecules of the human embryo and neonate. The synthetic, regulatory and export components for capsule expression are encoded in three functionally distinct gene blocks or regions of the 20 kb kps 'pathogenicity island'. These regions are organized as two convergently transcribed operons inserted into the monocistronic tRNA gene, pheV. The six genes of the so-called region 1 operon are transcribed in the same direction as pheV, and at least four of these genes are required for polysialic acid export. Expression of this operon is thermoregulated by transcriptional control of its first gene, kpsF. To investigate the function of region 1 further, two independent chromosomal disruptions were engineered by inserting promoterless, terminatorless kanamycin or chloramphenicol resistance cassettes into the HindIII site of the kpsF coding sequence. The chromosomal insertions were regulated by temperature in the same way as the wild-type operon, demonstrating that this control mechanism remained intact in these mutants. Chemical, immunological and ultrastructural microscopical methods demonstrated that full-length polysialic acid chains were synthesized but not exported by the kpsF mutants. This phenotype was correlated with decreased plaque diameter when the mutants were infected with the capsule-specific bacteriophage K1F. The export defect could not be complemented in trans with kpsF þ containing its cis-regulatory region because of titration of an apparent positive regulator of region 1 expression, whereas complementation was observed with a plasmid expressing kpsF from a physiologically irrelevant promoter. An N-terminal polyhistidine peptide was attached to KpsF and used to purify the overproduced polypeptide. Antibodies raised against KpsF identified at least one of its paralogues in E. coli, GutQ, suggesting that KpsF and its homologues are membrane associated. The results indicate the requirement for a precise balance between region 1 components of the capsule export machinery, and that KpsF plays a positive role in the assembly, operation or regulation of this apparatus.

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“…The spermidine/putrescene transport cluster of group IV is a member of a group of membrane-bound transporters that span the periplasm in Gram-negative bacteria. These genes belong to a superfamily of ATPbinding cassette transporters that import polyamines (Boos and Lucht 1996). The molecular chaperones of group V monitor and respond to the state of protein folding for non-native polypeptide substrates and nascent chain polypeptides (Mayhew and Hartl 1996).…”

Section: Discussionmentioning

confidence: 99%

Conserved Gene Clusters in Bacterial Genomes Provide Further Support for the Primacy of RNA

et al. 1997

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Abstract. Five complete bacterial genome sequences have been released to the scientific community. These include four (eu)Bacteria, Haemophilus influenzae, Mycoplasma genitalium, M. pneumoniae, and Synechocystis PCC 6803, as well as one Archaeon, Methanococcus jannaschii. Features of organization shared by these genomes are likely to have arisen very early in the history of the bacteria and thus can be expected to provide further insight into the nature of early ancestors. Results of a genome comparison of these five organisms confirm earlier observations that gene order is remarkably unpreserved. There are, nevertheless, at least 16 clusters of two or more genes whose order remains the same among the four (eu)Bacteria and these are presumed to reflect conserved elements of coordinated gene expression that require gene proximity. Eight of these gene orders are essentially conserved in the Archaea as well. Many of these clusters are known to be regulated by RNA-level mechanisms in Escherichia coli, which supports the earlier suggestion that this type of regulation of gene expression may have arisen very early. We conclude that although the last common ancestor may have had a DNA genome, it likely was preceded by progenotes with an RNA genome.

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Prokaryotic Binding Protein‐Dependent ABC Transporters

Cited by 72 publications

References 0 publications

Simple models for the analysis of binding protein‐dependent transport systems

Simple models for the analysis of binding protein‐dependent transport systems

Reduced polysialic acid capsule expression in Escherichia coli K1 mutants with chromosomal defects in kpsF

Conserved Gene Clusters in Bacterial Genomes Provide Further Support for the Primacy of RNA

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