Biomedical subjects

A Filloux

Publications and source records attributed to A Filloux.

25 records · Page 2Linked to original sources

PubMed1991

Conservation of xcp genes, involved in the two-step protein secretion process, in different Pseudomonas species and other gram-negative bacteria.

The two-step protein secretion pathway in Pseudomonas aeruginosa is dependent on the xcp genes. We investigated whether a similar secretion mechanism is present in non-pathogenic Pseudomonas spp. and in other gram-negative bacteria. The plant growth stimulating Pseudomonas strains P. putida WCS358, P. fluorescens WCS374 and Pseudomonas B10 appeared to secrete proteins into the extracellular medium. Southern hybridization experiments showed the presence of xcp genes in these strains and also in other gram-negative bacteria, including Xanthomonas campestris. Complementation experiments showed that the xcp gene cluster of P. aeruginosa restored protein secretion in an X. campestris secretion mutant. The secretion gene cluster of X. campestris however, restored secretion capacity in P. aeruginosa mutants only to a low degree. Two heterologous proteins were not secreted by P. fluorescens and P. aeruginosa. The results suggest the presence of a similar two-step protein secretion mechanism in different gram-negative bacteria, which however, is not always functional for heterologous proteins.

Bacterial Proteins↗

PubMed1990

Protein secretion in gram-negative bacteria: transport across the outer membrane involves common mechanisms in different bacteria.

The xcp genes are required for protein secretion by Pseudomonas aeruginosa. They are involved in the second step of the process, i.e. the translocation across the outer membrane, after the exoproteins have reached the periplasm in a signal peptide dependent fashion. The nucleotide sequence of a 2.5 kb DNA fragment containing xcp genes showed at least two complete open reading frames, potentially encoding proteins with molecular weights of 41 and 19 kd. Products with these apparent molecular weights were identified after expression of the DNA fragment in vitro and in vivo. Subcloning and complementation experiments showed that both proteins are required for secretion. The two products are located in the inner membrane and share highly significant homologies with the PulL and PulM proteins which are required for the specific secretion of pullulanase in Klebsiella pneumoniae. These homologies reveal the existence of a common mechanism for protein secretion in Pseudomonas aeruginosa and Klebsiella pneumoniae.

Amino Acid Sequence↗

PubMed1990

Cloning of the Pseudomonas aeruginosa alkaline protease gene and secretion of the protease into the medium by Escherichia coli.

Pseudomonas virulence is thought to depend on multiple characteristics, including the production of an extracellular alkaline protease. We report the isolation, from a PAO1 DNA genomic bank, of a cosmid carrying the structural gene coding for alkaline protease. By in vivo mutagenesis using transposon Tn1735, which functions as a transposable promoter, the expression of an 8.8-kilobase DNA fragment under control the tac promoter was obtained. When expressed in Escherichia coli, active alkaline protease was synthesized and secreted to the extracellular medium in the absence of cell lysis.

Cloning, Molecular↗

PubMed1989

Cloning of xcp genes located at the 55 min region of the chromosome and involved in protein secretion in Pseudomonas aeruginosa.

Pleiotropic mutations (xcp) affecting secretion of proteins in Pseudomonas aeruginosa have been previously characterized and mapped at 0 min, 55 min and 65 min. Genomic libraries of this organism have been constructed and the genes xcp-5 and xcp-54, located at the 55 min region, were cloned using the adjacent met allele as a marker, and complementation of xcp strains. From our linkage and cloning analysis, the most probable gene order in this region appears to be pyrD... xcp-5/xcp-54/met-9011/oru-314/trpF/leu-10. Restriction mapping and transposon (Tn1725) insertion mutagenesis demonstrated that: (i) the overall size of DNA necessary for xcp expression was 9kb, (ii) the two loci are not adjacent on the chromosome, and (iii) the two loci are expressed independently. The xcp-5 gene has been subcloned on a 4kb EcoRI fragment.

Bacterial Proteins↗

PubMed1988

Phosphate regulation in Pseudomonas aeruginosa: cloning of the alkaline phosphatase gene and identification of phoB- and phoR-like genes.

In Pseudomonas aeruginosa, phosphate limitation results in the synthesis of several protein species. We report the cloning of the P. aeruginosa alkaline phosphatase structural gene, phoA, and we show that this gene is regulated normally in Escherichia coli. We have also identified and cloned two P. aeruginosa genes which can complement phoB and phoR mutations in E. coli. This suggests that a pho regulon system similar to that in E. coli may exist in P. aeruginosa, using at least two similar regulatory factors.

Alkaline Phosphatase↗

PubMedDate not supplied

Secretion of extracellular proteins by Pseudomonas aeruginosa.

Pseudomonas aeruginosa is a bacterial species of commercial value secreting numerous extracellular proteins, involved in pathogenesis. Most strains produce at least a lipase, a phospholipase, an alkaline phosphatase, an exotoxin and 2 proteases (elastase and alkaline protease). Various mechanisms for secretion of exoproteins appear to exist in P aeruginosa. Genetic analysis has led to the identification of 2 secretion pathways: i) a "general" secretion pathway, defined by the xcp mutations, which mediates secretion of most extracellular proteins, and; ii) an independent secretion pathway specific for alkaline protease. Our present knowledge on the pathways and components of the secretion machinery in P aeruginosa is reviewed in this article.

Amino Acid Sequence↗

PubMedDate not supplied

Use of colicin-based genetic tools for studying bacterial protein transport.

Transport of proteins across the envelope of Gram-negative bacteria is a very challenging domain of investigation, which involves membrane-embedded proteinaceous complexes at which specific targeting occurs. These transporters (translocon or secreton) have been studied both with genetics and biochemistry. In this review we report recent developments that should help to identify novel interactions that exist within these complexes, and to decipher the signals that specifically direct transported proteins to the cognate system. These developments are exclusively based on the re-routing of colicins to these molecular machineries. The re-routing induces a lethal situation in the case of efficient or inefficient transport, depending on the system, thus creating a genetic tool for selection of mutations that correct or generate a transport default.

Bacterial Proteins↗