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C F Higgins

Publications and source records attributed to C F Higgins.

At least 181 records · Page 10Linked to original sources
PubMed1984

Genetic characterization and molecular cloning of the tripeptide permease (tpp) genes of Salmonella typhimurium.

Of the three bacterial peptide transport systems only one, the oligopeptide permease, has been characterized in any detail. We have now isolated Salmonella typhimurium mutants deficient in a second transport system, the tripeptide permease (Tpp), using the toxic peptide alafosfalin. Alafosfalin resistance mutations map at three loci, the gene encoding peptidase A (pepA) and two transport-defective loci, tppA and tppB. Locus tppA has been mapped to 74 min on the S. typhimurium chromosome, cotransducible with aroB, and is a positive regulator of tppB. Locus tppB maps at 27 min in the cotransduction gap between purB and pyrF. We cloned tppB, the structural locus for the tripeptide permease. Two simple methods are described for mapping the location of cloned DNA fragments on the chromosome of S. typhimurium.

Alanine↗
PubMed1984

Anaerobic and leucine-dependent expression of a peptide transport gene in Salmonella typhimurium.

Using Mu d1-mediated lac operon fusions, we studied the transcriptional regulation of the genes encoding two peptide transport systems, the oligopeptide permease and the tripeptide permease. The four opp genes were found to be constitutively expressed, whereas the genes encoding the tripeptide permease are under a complex set of regulatory controls. Two loci, tppA and tppB, are required for tripeptide permease function. Locus tppA is shown to be a positive regulator of tppB expression. In addition, tppB expression is specifically induced by exogeneous leucine or by anaerobiosis. Anaerobic induction of tppB is independent of the fnr gene product which is required for the anaerobic expression of several respiratory enzymes. Thus, there must be at least two distinct pathways for the anaerobic regulation of gene expression.

Anaerobiosis↗
PubMed1984

Proline uptake through the major transport system of Salmonella typhimurium is coupled to sodium ions.

Strains of Salmonella typhimurium deficient in one or more of the proline transport systems have been constructed and used to study the mechanism of energy coupling to transport. Proline uptake through the major proline permease (PP-I, putP) is shown to be absolutely coupled to Na+ ions and not to H+ ions as has previously been assumed. Transport through the minor proline permease (PP-II, proP), however, is unaffected by the presence or absence of Na+. The effect of Na+ on the kinetics of proline uptake shows that external Na+ increases the Vmax for transport. It seems probable that proline transport through PP-I is also coupled to Na+ ions in Escherichia coli.

Amino Acid Transport Systems, Neutral↗
PubMed1983

Genetic map of the opp (Oligopeptide permease) locus of Salmonella typhimurium.

The uptake of peptides by Salmonella typhimurium is mediated by three apparently independent transport systems. One of these systems, the oligopeptide permease, is encoded by a genetic locus (opp) which has been mapped at 34 min on the S. typhimurium chromosomal map. We accurately mapped the location of opp by cotransduction frequencies and by deletion analysis and show that the gene order for this region of the chromosome is cysB-trp-tonB-opp-galU-tdk. All opp mutants, independently isolated by a variety of means, mapped at this one locus, between tonB and galU. Spontaneous and transposon Tn10-generated deletions were used to construct a fine-structure genetic map of opp. Evidence is presented which indicates that opp covers a 5- to 6-kb segment of DNA and is therefore likely to consist of more than one gene.

Bacterial Proteins↗
PubMed1983

Periplasmic protein associated with the oligopeptide permeases of Salmonella typhimurium and Escherichia coli.

A periplasmic protein essential for the function of the oligopeptide transport system of Salmonella typhimurium was identified. This protein, encoded by the oppA gene, is one of the most abundant proteins in the periplasm and, with an apparent molecular weight of 52,000, is considerably larger than any other known periplasmic transport component. A similarly abundant periplasmic protein forms part of the oligopeptide transport system of Escherichia coli.

Bacterial Proteins↗
PubMed1982

Extensive homology between membrane-associated components of histidine and maltose transport systems of Salmonella typhimurium and Escherichia coli.

A strong homology was found between the amino acid sequences, deduced from DNA nucleotide sequences, of cytoplasmic membrane-associated components of the high affinity histidine transport system of Salmonella typhimurium (coded by the hisP gene) and the maltose-maltodextrin transport system of Escherichia coli (coded by the malK gene). When the HisP protein sequence was aligned with that of the NH2-terminal two-thirds of the MalK protein, 32% of the positions were identical, and an additional 35% were occupied by functionally similar amino acid residues. These results suggest that some, and possibly many, "periplasmic-binding protein-dependent" transport systems have evolved from a common ancestral system.

ATP-Binding Cassette Transporters↗
PubMed1982

Complete nucleotide sequence and identification of membrane components of the histidine transport operon of S. typhimurium.

The nucleotide sequence of the entire histidine transport operon from Salmonella typhimurium has been determined and is shown to consist of four genes, hisJ, hisQ, hisM and hisP. This operon provides the only example of a binding protein-dependent transport system for which the total number of protein components is known. Determination of the amino acid compositions and sequences of these four transport proteins, together with analysis of various transport mutants, allows us to propose a molecular model for binding protein-dependent transport.

Amino Acid Sequence↗
PubMed1982

Regulatory regions of two transport operons under nitrogen control: nucleotide sequences.

We have determined the nucleotide sequences of the regulatory regions from two amino acid transport operons from Salmonella typhimurium: dhuA, which regulates the histidine transport operon, and argTr, which regulates argT, the gene encoding the lysine-arginine-ornithine-binding protein, LAO. The promoter for the histidine transport operon has been identified from the sequence change in the promoter-up mutation dhuA1. Neither regulatory region has any of the features typical of the regulatory regions of the amino acid biosynthetic operons, indicating that regulation of at least these transport genes does not involve a transcription attenuation mechanism. We have identified three interesting features, present in both of these sequences, which may be of importance in the regulation of these and other operons: a "stem-loop-foot" structure, a region of specific homology, and a mirror symmetry. The region of mirror symmetry may be a protein recognition site important is regulating expression of these and other operons in response to nitrogen availability. Mirror symmetry as a structure for DNA-protein interaction sites has not been proposed previously.

Amino Acids↗
PubMed1981

Two periplasmic transport proteins which interact with a common membrane receptor show extensive homology: complete nucleotide sequences.

The hisJ and argT genes of Salmonella typhimurium encode two periplasmic binding proteins, J and LAO, which are involved in histidine and arginine transport, respectively, and which interact with a common membrane-bound component, the P protein. The complete nucleotide sequences of these two genes have been determined. The two genes show extensive homology (70%) and presumably arose by tandem duplication of a single ancestral gene. The two encoded proteins now perform distinct functions but still retain sufficient homology to permit interaction with the same site on the membrane-bound P protein. Three lines of evidence have allowed both the amino acid-binding site and the site involved in the interaction with the P protein to be assigned to specific regions of each binding protein: (i) the distribution of amino acid differences between the two proteins; (ii) the properties of a functional chimeric protein, produced by a deletion mutant in which the first half of the argT gene is fused to the second half of the hisJ gene; (iii) the sequence change in a mutant J protein unable to interact with P.

Amino Acid Sequence↗
PubMed1981

The Peptide pools of germinating barley grains: relation to hydrolysis and transport of storage proteins.

A quantitative procedure for purifying small peptides from plant tissues, involving both ion-exchange and gel-exclusion chromatography, is described. Peptides were quantified and characterized by using the fluorescence reagents dansyl chloride and fluorescamine. Large pools of small peptides and amino acids have been identified in both the endosperm and embryo of germinating barley grains. The peptide pool of the endosperm increases during the first 3 days of germination, subsequently decreasing, an observation compatible with a role for peptides as intermediates in the breakdown of the storage proteins and their transfer to the embryo. The amino acid composition of these peptides indicates that all the major classes of storage protein contribute to the pool. The concentration of peptides produced in the endosperm during germination is sufficient for the efficient operation of the peptide transport system of the scutellar membrane characterized previously (Higgins and Payne, Planta 136: 71-76, 1977; Planta 138: 211-215 and 217-221, 1978). Data presented here indicate that peptides play at least as important a role as amino acids in the transfer of stored nitrogen from the endosperm to the embryo during germination.

Journal Article↗
PubMed1981

Physical map of the Salmonella typhimurium histidine transport operon: correlation with the genetic map.

A detailed restriction map of a 12.4-kilobase EcoRI fragment of Salmonella typhimurium deoxyribonucleic acid (DNA) containing the entire histidine transport operon and the argT gene is presented. Subclones of specific regions of the transport operon of S. typhimurium were constructed in plasmid vectors. An accurate correlation between the restriction map and the location of genetically defined deletions was obtained by hybridizing restriction digests of chromosomal DNA from strains carrying each deletion with cloned transport operon DNA as a probe. These data were used to position the histidine transport genes on the cloned 12.4-kilobase fragment of DNA.

Biological Transport↗
PubMedDate not supplied

ABC transporters: physiology, structure and mechanism--an overview.

ABC transporters form one of the largest of all protein families with a diversity of physiological functions. In Escherichia coli almost 5% of the genome is occupied by genes encoding components of these transporters, and there are examples in all species from microbes to man. In this overview, the importance of studies on bacteria in elucidating many basic principles pertaining to ABC transporters is emphasised. The family is described and a general overview of the structure and function of these transporters is presented.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMedDate not supplied

Multidrug transport by ATP binding cassette transporters: a proposed two-cylinder engine mechanism.

The elevated expression of ATP binding cassette (ABC) multidrug transporters in multidrug-resistant cells interferes with the drug-based control of cancers and infectious pathogenic microorganisms. Multidrug transporters interact directly with the drug substrates. This review summarizes current insights into the mechanism(s) by which ATP hydrolysis is coupled to drug transport in bacterial LmrA and its human homolog P-glycoprotein. In addition, the relevance of these insights for other ABC transporters will be discussed.

ATP Binding Cassette Transporter, Subfamily B↗
PubMedDate not supplied

Peptide chemotaxis in E. coli involves the Tap signal transducer and the dipeptide permease.

Bacterial chemotaxis provides a simple model system for the more complex sensory responses of multicellular eukaryotic organisms. In Escherichia coli, methylation and demethylation of four related membrane proteins, the methyl-accepting chemotaxis proteins (or MCPs), is central to chemotactic sensing and signal transduction. Three of these proteins, Tar, Tsr and Trg, have been assigned specific roles in chemotaxis. However, the role of the fourth MCP, Tap, has remained obscure. We demonstrate here that Tap functions as a conventional signal transducer, enabling the cell to respond chemotactically to dipeptides. This provides the first evidence of specific bacterial chemotaxis towards peptides. Peptide taxis requires the function of a periplasmic component of the dipeptide permease. This protein represents the first example of a periplasmic chemoreceptor that does not have a sugar substrate.

Bacterial Proteins↗