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Biomedical subjects

P Germon

Publications and source records attributed to P Germon.

8 recordsLinked to original sources
PubMed1999

The Tol proteins of Escherichia coli and their involvement in the uptake of biomolecules and outer membrane stability.

The Tol proteins of Escherichia coli are involved in outer membrane stability. They are also required for the uptake of the group A colicins and the translocation of filamentous phage DNA into the cytoplasm. The tol-pal genes constitute two operons in the E. coli genome, orfltolQRA and tolBpalorf2. The TolQ TolR TolA proteins form a complex in the cytoplasmic membrane, while TolB and Pal interact near the outer membrane. Most of the amino acid residues of TolA, TolB, TolR and Pal are localized in the periplasm. Recent advances in the knowledge of interactions of Tol-Pal proteins with other envelope components, or with group A colicins, are presented, together with current hypotheses about the role of the Tol proteins in outer membrane stability.

Bacterial Proteins↗
PubMed1998

TolB protein of Escherichia coli K-12 interacts with the outer membrane peptidoglycan-associated proteins Pal, Lpp and OmpA.

The Tol-Pal proteins of Escherichia coli are involved in maintaining outer membrane integrity. Transmembrane domains of TolQ, TolR and TolA interact in the cytoplasmic membrane, while TolB and Pal form a complex near the outer membrane. TolB and the central domain of TolA interact in vitro with the outer membrane porins. In this study, both genetic and biochemical analyses were carried out to analyse the links between TolB, Pal and other components of the cell envelope. It was shown that TolB could be cross-linked in vivo with Pal, OmpA and Lpp, while Pal was associated with TolB and OmpA. The isolation of pal and tolB mutants disrupting some interactions between these proteins represents at first approach to characterizing the residues contributing to the interactions. We propose that TolB and Pal are part of a multiprotein complex that links the peptidoglycan to the outer membrane. The Tol-Pal proteins might form transenvelope complexes that bring the two membranes into close proximity and help some outer membrane components to reach their final destination.

Amino Acid Sequence↗
PubMed1998

Mutational analysis of the Escherichia coli K-12 TolA N-terminal region and characterization of its TolQ-interacting domain by genetic suppression.

The Tol-Pal proteins of Escherichia coli are involved in maintaining outer membrane integrity. They form two complexes in the cell envelope. Transmembrane domains of TolQ, TolR, and TolA interact in the cytoplasmic membrane, while TolB and Pal form a complex near the outer membrane. The N-terminal transmembrane domain of TolA anchors the protein to the cytoplasmic membrane and interacts with TolQ and TolR. Extensive mutagenesis of the N-terminal part of TolA was carried out to characterize the residues involved in such processes. Mutations affecting the function of TolA resulted in a lack or an alteration in TolA-TolQ or TolR-TolA interactions but did not affect the formation of TolQ-TolR complexes. Our results confirmed the importance of residues serine 18 and histidine 22, which are part of an SHLS motif highly conserved in the TolA and the related TonB proteins from different organisms. Genetic suppression experiments were performed to restore the functional activity of some tolA mutants. The suppressor mutations all affected the first transmembrane helix of TolQ. These results confirmed the essential role of the transmembrane domain of TolA in triggering interactions with TolQ and TolR.

Amino Acid Sequence↗
PubMed1993

Metabolism of the herbicide atrazine by Rhodococcus strains.

Rhodococcus strains were screened for their ability to degrade the herbicide atrazine. Only rhodococci that degrade the herbicide EPTC (s-ethyl-dipropylthiocarbamate) metabolized atrazine. Rhodococcus strain TE1 metabolized atrazine under aerobic conditions to produce deethyl- and deisopropylatrazine, which were not degraded further and which accumulated in the incubation medium. The bacterium also metabolized the other s-triazine herbicides propazine, simazine, and cyanazine. The N dealkylation of triazine herbicides by Rhodococcus strain TE1 was associated with a 77-kb plasmid previously shown to be required for EPTC degradation.

Atrazine↗
PubMed1988

Adjunct endarterectomy of the left anterior descending coronary artery.

During a three-year period, complete revascularization of diffusely diseased left anterior descending (LAD) coronary arteries was accomplished by extensive endarterectomy in conjunction with bypass grafting in 37 patients in whom conventional bypass was not feasible. This group constituted 7.0% of all patients undergoing nonemergency coronary revascularization during this period. The left internal mammary artery was used to bypass the endarterectomized LAD artery in 22 patients. There was 1 (2.7%) operative death and 1 perioperative myocardial infarction. At follow-up, which was 100% with a mean of 41.4 months, all endarterectomy patients were in New York Heart Association Functional Class I or II. Twenty-four endarterectomy patients underwent first-pass radionuclide angiographic stress testing 20 months after operation. Twenty patients (83%) had excellent postoperative exercise tolerance, achieving 5 to 7 mets on treadmill testing. Left ventricular functional reserve was preserved, as evidenced by an increase of global ejection fraction from 48 +/- 15% at rest to 59 +/- 18% (p less than 0.005) with exercise. A similar increase was measured in the proximal and distal anterior wall segmental ejection fractions. No difference in response to exercise was found between the internal mammary artery and the vein graft groups. Thus, complete revascularization of the diffusely diseased LAD artery can be accomplished by adjunct endarterectomy without added morbidity or mortality and with excellent functional results.

Adult↗
PubMed1981

Ventricular function before and after mitral valve replacement.

To evaluate right ventricular function following mitral valve replacement, we studied 84 patients with isolated mitral valve disease with the use of first-pass radionuclide angiography before, 1 week after, and up to 1 year after operation. The right ventricular ejection fraction for the entire group improved from 29% +/- 11% to 43% +/- 10% (p less than 0.001) at 1 week. This increase was maintained at 3 months (41% +/- 10%) and up to year after operation (40% +/- 12%). The improvement was found not to be influenced by either the type of valvular lesion or the presence and/or level of pulmonary hypertension. When the patients were grouped according to the type of prosthetic valve placed at operation, the right ventricular ejection fraction increased in all patients within 1 week of operation, with sustained improvement at 3 months postoperatively. Thereafter, it began to decline in patients receiving a Carpentier bioprosthesis while being maintained in those patients who received disc valves. Further analysis revealed that those patients who receiving the larger Carpentier bioprostheses had a greater deterioration of right ventricular function than those receiving the smaller Carpentier valves. Left ventricular function in the entire group was normal preoperatively (62% +/- 16%) and was unchanged at 1 week (60% +/- 16%) and a 1 year (59% +/- 16%) after operation.

Adult↗