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Biomedical subjects

G Lépine

Publications and source records attributed to G Lépine.

9 recordsLinked to original sources
PubMed2000

MglA and mglB of Treponema denticola; similarity to ABC transport and spa genes.

The mglA and mglB genes (td-mglA and td-mglB) of the oral spirochete Treponema denticola were sequenced. These two T. denticola genes are highly homologous to the E. coli and Treponema pallidum mglA and mglB genes which are part of the three gene beta-methylgalactoside transport operon, mglBAC. Both Td-mglA and td-mglB are also homologous to the high affinity ABC-type transporters for ribose and arabinose, and surface presentation antigens (spa) locus, part of the type III secretion systems in enteropathogens. Td-mglB and td-mglA are co-transcribed as a single mRNA in T. denticola as well as in E. coli cells as determined by reverse transcription PCR (RT-PCR). Homology to td-mglB and its expressed protein was found in other oral spirochetes as determined by Southern and western blot analysis.

ATP-Binding Cassette Transporters↗
PubMed1998

Epithelial cell invasion by Actinobacillus actinomycetemcomitans strains from restriction fragment-length polymorphism groups associated with juvenile periodontitis or carrier status.

The epithelial cell invasiveness of Actinobacillus actinomycetemcomitans strains of different restriction fragment-length polymorphism (RFLP) groups associated with disease conversion and asymptomatic carrier status in localized juvenile periodontitis was examined. Twenty clinical isolates were studied for their ability to invade KB monolayers, using the quantitative gentamicin killing assay. Five isolates were found to be invasive, five were not invasive; and the other 10 did not invade better than an invasion negative control Haemophilus aphrophilus strain ATCC 19415. Using probe-specific DNA fingerprinting. 11 strains were assigned to RFLP group II (disease-associated); 4 to RFLP type XIII (carrier status associated); and the other to groups III, IV, V and VII. Eight isolates, all RFLP group II, were leukotoxin producers as determined by PCR amplification of the lkt promoter region. No correlation was found between invasiveness and RFLP group. Leukotoxin production was more associated with noninvasive than invasive strains.

Aggregatibacter actinomycetemcomitans↗
PubMed1997

In vitro models that support adhesion specificity in biofilms of oral bacteria.

Adhesion to adsorbed pellicles and interspecies co-adhesion to form plaque biofilms involve selective interactions of bacterial adhesins with specific receptors. Our laboratory has devised in vitro assays for co-adhesion between Actinomyces naeslundii and Streptococcus oralis or Porphyromonas gingivalis on saliva-coated mineral and hexadecane droplet substrata. P. gingivalis structures significant for co-adhesion with A. naeslundii include surface vesicles and fimbriae. A family of arginine-specific cysteine proteinases in vesicles may be involved in adherence to bacteria, to host cells, and to matrix proteins. New research from several laboratories has found that such proteinases are processed from genes encoding polyproteins containing both proteinase and hemagglutinin domains. In addition to enzyme-substrate recognition, bacterial adhesion is often determined by specific protein-peptide and lectincarbohydrate recognition. A. naeslundii--salivary prolinerich protein, S. gordonii--salivary alpha-amylase, and Treponema denticola--matrix protein recognition are examples of the former. Co-adhesion of A. naeslundii and S. oralis is an example of the latter. Lactose can selectively desorb A. naeslundii cells from mixed biofilms with S. oralis, a demonstration of the significance of specificity. Although non-specific forces are probably secondary to stereochemical fit in determining the selective range of surfaces that bacteria have evolved to recognize and bind, they probably help stabilize non-covalent bonds within aligned, complementary domains.

Actinomyces viscosus↗
PubMed1996

Duplication and differential expression of hemagglutinin genes in Porphyromonas gingivalis.

A third hemagglutinin gene, defined as hagC, was cloned from Porphyromonas gingivalis 381 and sequenced. This gene was found to encode a protein highly homologous (98.6%) to the previously reported HagB hemagglutinin protein. The upstream and downstream regions of hagB and hagC were found to share less than 40% homology compared with 99% for their open reading frames. The antigenic relationship between the two hemagglutinins was demonstrated by Western blot analysis. When expressed in an in vitro transcription-translation system, both genes encoded a protein with a molecular mass of 49 kDa. As determined by reverse transcription polymerase chain reaction, the steady-state levels of hagB and hagC mRNAs were found to vary according to the growth phase and hemin concentration. The amount of transcripts decreased in hemin-limited conditions or in the absence of hemin. Furthermore, hagB mRNAs were detected in the early logarithmic growth phase compared with the hagC transcripts, which were detected only in the mid-exponential phase of growth.

Adhesins, Bacterial↗
PubMed1996

Construction and preliminary characterization of three hemagglutinin mutants of Porphyromonas gingivalis.

Targeted insertional mutagenesis was used to construct hagA, hagB, and hagC hemagglutinin mutants of Porphyromonas gingivalis. pJRD215-derived plasmids containing tetA(Q)2 and portions of the targeted genes were conjugated into P. gingivalis. Interruption of the three loci was confirmed by Southern hybridization, sequencing, reverse transcription-PCR, and microtiter hemagglutination assays. No significant differences in hydrophobicity or coadherence to Actinomyces viscosus were detected between the mutants and the wild-type strain.

Base Sequence↗
PubMed1995

The two alleles of the hapP gene in Physarum polycephalum code for different proteins.

Many mRNAs show cell-type specific expression in the acellular slime mold Physarum polycephalum. The most abundant plasmodial-specific mRNA (hapP) encodes a small hydrophobic protein of 187 amino acids that contains a potential signal peptide. Southern hybridizations using the hapP cDNA showed that the hapP gene is a single copy gene with two alleles, hapP1 and hapP2. The alleles have restriction enzyme polymorphisms. The nucleotide sequence of the coding region of the hapP1 allele was obtained from a genomic clone, and the nucleotide sequence of the hapP2 allele was obtained from a cDNA clone. The hapP1 and hapP2 alleles code for proteins that are 9.6% different in amino acid sequence. All differences are found in the central region of the protein. The nucleotide sequences of the first and last exons, which contain coding and non-coding regions, are identical. PCR amplification of cDNAs (RT-PCR) showed that both alleles are expressed in the same cell.

Alleles↗
PubMed1995

The cloning, expression and sequence analysis of a second Porphyromonas gingivalis gene that codes for a protein involved in hemagglutination.

It has been suggested that Porphyromonas gingivalis may possess more than one hemagglutinin. We have previously reported the cloning of a gene (hagA) that encodes a hemagglutinin. In this study we report the cloning, characterization, and sequencing of a second gene (hagB) that encodes a protein that also appears to be involved in hemagglutination. Antiserum to the clone (ST 7) was found to inhibit hemagglutination by P. gingivalis 381, and hemagglutinating inhibition activity of anti-P. gingivalis antiserum was reduced by adsorption of the antiserum with cells of clone ST 7. Restriction mapping and Southern analysis indicates there is little or no DNA homology between this cloned 4.8-kb HindIII DNA fragment and a cloned hemagglutinin gene we have previously described. Minicell analysis of the cloned P. gingivalis chromosomal DNA fragment revealed that the major gene product is a 49-kDa protein. Immunoaffinity chromatography using purified rabbit immunoglobulin G against the cloned protein resulted in the purification of a major reactive 49- to 50-kDa protein from a P. gingivalis cell lysate. Nucleotide sequence analysis revealed the hagB open reading frame to be 1053 nucleotides in length with a mol% G+C of 59.9% coding for a protein of 350 residues with a calculated molecular weight of 39.375 kDa. This protein was also determined to be basic and hydrophilic and to contain a potential signal peptide. Comparison of both the nucleotide and derived amino acid sequences with computer-based databases did not reveal any significant homologies between habB and any other previously sequenced genes.

Adhesins, Bacterial↗
PubMed1993

Sequencing of a tet(Q) gene isolated from Bacteroides fragilis 1126.

Recently, Tet Q, a tetracycline resistance determinant that confers resistance by a ribosome protection mechanism, was described and added to the two previously described classes, Tet M and Tet O. The first representative of this class, tetA(Q)1, was isolated from Bacteroides thetaiotaomicron DOT. We report the sequencing of a gene isolated from B. fragilis 1126 which also confers tetracycline resistance. Because of its high degree of identity (97%) with the tetA(Q)1 gene, we defined it as tetA(Q)2. MIC studies revealed that tetA(Q)2 provides a low level of resistance to tetracycline when cloned into Escherichia coli. The extensive homology between tetA(Q)1 and tetA(Q)2 supports the idea of a recent horizontal transfer of tet(Q) genes among Bacteroides spp.

Amino Acid Sequence↗