Biomedical subjects

Emmanuel Jamet

Publications and source records attributed to Emmanuel Jamet.

3 recordsLinked to original sources

PubMed2004

A xylose-inducible expression system for Lactococcus lactis.

A new controlled production system to target heterologous proteins to cytoplasm or extracellular medium is described for Lactococcus lactis NCDO2118. It is based on the use of a xylose-inducible lactococcal promoter, P(xylT). The capacities of this system to produce cytoplasmic and secreted proteins were tested using the Staphylococcus aureus nuclease gene (nuc) fused or not to the lactococcal Usp45 signal peptide. Xylose-inducible nuc expression is tightly controlled and resulted in high-level and long-term protein production, and correct targeting either to the cytoplasm or to the extracellular medium. Furthermore, this expression system is versatile and can be switched on or off easily by adding either xylose or glucose, respectively. These results confirm the potential of this expression system as an alternative and useful tool for the production of proteins of interest in L. lactis.

Gene Expression Regulation, Bacterial↗

PubMed2003

Transmembrane modulator-dependent bacterial tyrosine kinase activates UDP-glucose dehydrogenases.

Protein-tyrosine kinases regulating bacterial exopolysaccharide synthesis autophosphorylate on tyrosines located in a conserved C-terminal region. So far no other substrates have been identified for these kinases. Here we demonstrate that Bacillus subtilis YwqD not only autophosphorylates at Tyr-228, but that it also phosphorylates the two UDP-glucose dehydrogenases (UDP-glucose DHs) YwqF and TuaD at a tyrosine residue. However, phosphorylation of YwqF and TuaD occurs only in the presence of the transmembrane protein YwqC. The presumed intracellular C-terminal part of YwqC (last 50 amino acids) seems to interact with the tyrosine-kinase and to allow YwqD-catalysed phosphorylation of the two UDP-glucose DHs, which are key enzymes for the synthesis of acidic polysaccharides. However, only when phosphorylated by YwqD do the two enzymes exhibit detectable UDP-glucose DH activity. Dephosphorylation of P-Tyr-YwqF and P-Tyr-TuaD by the P-Tyr-protein phosphatase YwqE switched off their UDP-glucose DH activity. YwqE, which is encoded by the fourth gene of the B.subtilis ywqCDEF operon, also dephosphorylates P-Tyr-YwqD.

Amino Acid Sequence↗

PubMed2002

Gene regulation in Lactococcus lactis: the gap between predicted and characterized regulators.

The genome sequence of Lactococcus lactis IL 1403 was previously determined with high quality, allowing a reliable determination of the potential ORFs present in the genome. It encodes 2310 proteins, and 138 of them were assigned as potential regulators, half of which being further classified by their similarity to known protein families. Among these regulators, most could have a direct role as transcriptional regulators, while the others may have less well defined functions in transcriptional regulation or more general functions, such as the GTP binding protein family. Current knowledge related to the regulators controlling gene expression in L. lactis will be confronted to data obtained in other bacteria. For example, comparison of the L. lactis regulators with those of B. subtilis reveals many orthologous regulators and also some clear differences in the type of regulator used in the two bacteria. Further comparison of the role and the effectors of orthologous regulators shows that direct transposition of a 'heterologous model' does not allow to build a reliable regulatory network in L. lactis. Moreover, many L. lactis regulators have functions that could not be proposed by transposition of the knowledge currently available in other bacteria. A considerable amount of work will be necessary to assess the function of L. lactis regulators and build a comprehensive model of the regulatory network. This would provide invaluable information on L. lactis biology and the way this bacterium interacts with the environment.

Bacterial Proteins↗