Yersinia enterocolitica type III secretion: Evidence for the ability to transport proteins that are folded prior to secretion
1 Max von Pettenkofer-Institut, Pettenkoferstr. 9a, D-80336 München, Germany
2 Max-Planck-Institut für molekulare Genetik, Ihnestrasse 73, D-14195 Berlin, Germany
3 Limnos, Podlimbarskega 31, SI-1000 Ljubljana, Slovenia
BMC Microbiology 2004, 4:27 doi:10.1186/1471-2180-4-27Published: 12 July 2004
Pathogenic Yersinia species (Y. enterocolitica, Y. pestis, Y. pseudotuberculosis) share a
In this study we have fused YopE secretion signals of various length to the mouse dihydrofolate reductase (DHFR) in order to analyse the DHFR folding state prior to secretion. We could demonstrate that secretion-deficient as well as secretion-competent YopE-DHFR fusions complexed to SycE can be efficiently purified from Yersinia cytosol by affinity chromatography using methotrexate-agarose. This implies the folding of the DHFR fusion moiety despite SycE binding and contradicts the previously presented model of folding inhibition by chaperone binding. Secretion-deficient YopE-DHFR fusions caused severe jamming of the TTSS. This observation contradicts the co-translational secretion model.
We present evidence that the Yersinia TTSS is familiar with the processing of transport substrates which are folded prior to secretion. We therefore predict that an unfoldase is involved in type III secretion.