Biomedical subjects

Nicola Fitchen

Publications and source records attributed to Nicola Fitchen.

3 recordsLinked to original sources

PubMed2005

All subtypes of the cytotoxin VacA adsorb to the surface of Helicobacter pylori post-secretion.

The major secreted virulence factor of Helicobacter pylori, the vacuolating cytotoxin VacA, is known to insert into eukaryotic membranes and has been observed in association with the surface of H. pylori cells that are actively producing it. Here, it is demonstrated that VacA is capable of interacting with the surface of H. pylori and Escherichia coli after secretion. It is shown that this interaction is resistant to disruption of electrostatic and hydrophobic forces, and that it appears to occur despite truncation of LPS and the removal of trypsin-accessible surface proteins. Adsorption to bacterial cell surfaces was independent of the VacA subtype, suggesting that it is not mediated through recognition of a known receptor by the VacA p58 subunit. Similarly, adsorption to bacterial cell surfaces is unlikely to be instigated by the extreme N-terminus of VacA, since a hydrophilic extension at this location that is known to disrupt VacA-induced vacuolation did not interfere with adsorption to H. pylori cells.

Adsorption↗

PubMed2003

Functional complementation of E. coli secD and secG mutants by Helicobacter pylori homologues.

The Sec machinery is one mechanism used by bacteria to translocate proteins across their cytoplasmic membrane. Most of the Sec components have been identified within the important gastric pathogen, Helicobacter pylori, however their functionality has not yet been demonstrated. Here we report the existence of putative homologues to the Sec components yajC (HP1450) and yidC (HP1551), and demonstrate the ability of the H. pylori secD (HP1550) and secG (HP1255) homologues to facilitate inner membrane translocation of the maltose-binding protein MalE, by complementation of the respective secretion-deficient Escherichia coli mutants, thus providing evidence of their functionality.

Amino Acid Sequence↗

PubMed2003

Electrostatic sensor for identifying interactions between peptides and bacterial membranes.

The use of the membrane probe fluorescein phosphatidylethanolamine (FPE) to investigate membrane binding is well established. However, until now, its use has been restricted to studies involving peptides and eukaryotic membranes. This useful tool has been developed to interrogate peptide:prokaryotic membrane interactions by introducing novel methodology to incorporate FPE into the membranes of UV killed, whole bacterial cells. The electrostatic potential of the membrane in the immediate vicinity of the probe affects the protonation state of the xanthene ring system in the fluorescein head group, which is held close to the membrane surface. When altered, e.g. by peptide binding and insertion, a change in fluorescence results, which can be measured spectrophotometrically. Applicability of this technique to bacterial surface interactions was confirmed by production of a binding curve for both a synthetic peptide and a 37kDa protein. Future investigations are anticipated to utilize this technology to characterize interactions of other toxins plus antimicrobial peptides such as lactoferricin and defensins with their target membranes.

Bacteria↗