Etude du système de sécrétion de type VI chez Escherichia coli entéro-agrégatif : Caractérisation d'un sous complexe d'ancrage membranaires

• Auteur / Autrice : Marie-Stéphanie Aschtgen
• Direction : Eric Cascales
• Type : Thèse de doctorat
• Discipline(s) : Biologie, Spécialité Microbiologie
• Date : Soutenance le 16/12/2011
• Etablissement(s) : Aix-Marseille 2
• Ecole(s) doctorale(s) : École Doctorale Sciences de la vie et de la santé (Marseille)
• Partenaire(s) de recherche : Laboratoire : Laboratoire d’Ingénierie des Systèmes Macromoléculaires (Marseille)
• Jury : Président / Présidente : Cheng-Cai Zhang
• Jury : Examinateurs / Examinatrices : Eric Cascales, Cheng-Cai Zhang, Françoise Jacob-Dubuisson, Joseph Mougous, Ivo Gomperts-Boneca, Andréa Dessen
• Jury : Rapporteurs / Rapporteuses : Françoise Jacob-Dubuisson, Joseph Mougous

Mots clés

Mots clés contrôlés

Paroi bactérienne

Escherichia coli

Bactéries Gram négatives

Mots clés libres

Système de sécrétion de type VI

Eaec

Complex membranaire

Type VI secretion system

Eaec

Membrane complex

Résumé

Bacterial pathogenesis relies on a subset of mechanisms including adhesion to various matrices, antibiotic resistance, defence and action against surrounding microorganisms, and secretion of virulence factors. Among the secretion systems, the recently identified Type VI secretion system (T6SS) has been shown to be involved in both virulence against eukaryotic cells and inter-bacterial warfare. T6SS are composed of a minimum of 13 proteins called ''core components''. It is believe to form a macromolecular system that spans the envelope to assemble an extracellular structure composed of the Hcp protein with a trimer of VgrG located at the tip. This model has been built following in silico and structural analyses demonstrating the link between several T6SS subunits and bacteriophage T4 baseplate and tail elements. Other T6SS subunits include membrane proteins. Using enteroaggregative Escherichia coli as a bacterial model, the aim of my work is to understand how this system assembles in the cell envelope. I recently showed that four of these membrane proteins, SciP, SciS, SciN and SciZ make contact to form a complex [1]. These four subunits are critical components of the T6SS. I then delineated the interaction network, demonstrating that SciZ interacts with SciP, and that SciS interacts with both SciP and SciN. Further characterization of these subunits showed that SciN is a lipoprotein associated with the outer membrane [2, 4], whereas SciP and SciS are inner membrane proteins anchored through a single and three transmembrane segments respectively. SciZ is a polytopic inner membrane protein carrying a peptidoglycan-binding motif within its periplasmic domain. Mutagenesis and peptidoglycan binding experiments demonstrated that SciZ anchors the T6SS to the cell wall [1, 3]. Overall, we have identified and characterized a trans-envelope complex anchored in both membrane and to the peptidoglycan layer.