A conserved α-helix essential for a type VI secretion-like system of Francisella tularensis
2009 (English)In: Journal of Bacteriology, ISSN 0021-9193, E-ISSN 1098-5530, Vol. 191, no 8, 2431-2446 p.Article in journal (Refereed) Published
Francisella tularensis harbors genes with similarity to genes encoding components of a type VI secretion system (T6SS) recently identified in several gram-negative bacteria. These include iglA and iglB, the homologues of which are conserved in most T6SSs. We used a yeast two-hybrid system to study the interaction of the Igl proteins of F. tularensis LVS. We identified a region of IglA, encompassing residues 33-132, necessary for efficient binding to IglB as well as for IglAB protein stability and intra-macrophage growth. In particular, residues 103-122, overlapping with a highly conserved alpha-helix, played an absolutely essential role. Point mutations within this domain caused modest defects in IglA-IglB binding in yeast, but markedly impaired intra-macrophage replication and phagosomal escape, resulting in severe attenuation of LVS in mice. Thus, IglA-IglB complex formation is clearly crucial for Francisella pathogenicity. This interaction may be universal to T6S, since IglAB homologues of Yersinia pseudotuberculosis, Pseudomonas aeruginosa, Vibrio cholerae, Salmonella typhimurium and Escherichia coli were also shown to interact in yeast and the interaction was dependent on the preservation of the same alpha-helix. Heterologous interactions formed between non-native IglAB proteins further supported the notion of a conserved binding site. Thus, IglA-IglB complex formation is clearly crucial for Francisella pathogenicity and the same interaction is conserved in other human pathogens.
Place, publisher, year, edition, pages
2009. Vol. 191, no 8, 2431-2446 p.
pathogenicity island; protein secretion; escherichia-coli; yersinia-pestis; pseudomonas-aeruginosa; edwardsiella-tarda; virulence factors; vibrio-cholerae; live vaccine; escape
IdentifiersURN: urn:nbn:se:umu:diva-19549DOI: 10.1128/JB.01759-08PubMedID: 19201795OAI: oai:DiVA.org:umu-19549DiVA: diva2:202024