Intimin and invasin export their C-terminus to the bacterial cell surface using an inverse mechanism compared to classical autotransport.
Invasin and intimin are major virulence factors of enteropathogenic Yersiniae and Escherichia coli, mediating invasion into and intimate adherence to host cells, respectively. Several studies have hinted that extracellular portion of these homologous proteins might be exported via an autotransport mechanism, but rigorous experimental proof has been lacking. Here, we present a topology model for invasin and intimin, consistent with the hypothesis that the N-terminal β-barrel domain acts as a translocation pore to secrete the C-terminal passenger domain. We confirmed this topology model by inserting epitope tags into the loops of the β-barrel. We further show that obstructing the pore of β-barrel hinders the export of the passenger domain. As for classical autotransport, the biogenesis of invasin and intimin is dependent on the Bam complex and the periplasmic chaperone SurA, whereas the chaperone/protease DegP is involved in quality control. However, compared to classical autotransporters (Type Va secretion), the domain structure of intimin and invasin is inverted. We conclude that proteins of the intimin and invasin family constitute a novel group of autotransported proteins, and propose that this class of autotransporters be termed Type Ve secretion.
Institut für Medizinische Mikrobiologie und Hygiene, Universität Tübingen, Germany.
Philipp
P
Oberhettinger
Monika
M
Schütz
Jack C
JC
Leo
Nadja
N
Heinz
Jürgen
J
Berger
Ingo B
IB
Autenrieth
Dirk
D
Linke
D018829:Adhesins, Bacterial / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015153:Blotting, Western; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D002942:Circular Dichroism; D019295:Computational Biology; D054308:Enteropathogenic Escherichia coli / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D005434:Flow Cytometry; D006367:HeLa Cells; D006801:Humans; D008856:Microscopy, Fluorescence; D016297:Mutagenesis, Site-Directed; D019696:Peptidylprolyl Isomerase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D037521:Virulence Factors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
D018829:Adhesins, Bacterial; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D037521:Virulence Factors; C053476:invasin, Yersinia; C073819:eaeA protein, E coli; C490900:SurA protein, E coli; D019696:Peptidylprolyl Isomerase