The assembly of the export apparatus (YscR,S,T,U,V) of the Yersinia type III secretion apparatus occurs independently of other structural components and involves the formation of an YscV oligomer

Authors

  • Andreas Diepold,

    1. Biozentrum, Universität Basel, Basel, Switzerland
    Search for more papers by this author
    • Present address: Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.

  • Ulrich Wiesand,

    1. Biozentrum, Universität Basel, Basel, Switzerland
    Search for more papers by this author
  • Guy R. Cornelis

    Corresponding author
    1. Biozentrum, Universität Basel, Basel, Switzerland
      E-mail guy.cornelis@unibas.ch; Tel. secretary (+41) 61 267 21 21; Tel. direct (+41) 61 267 21 10; Fax (+41) 61 267 21 18.
    Search for more papers by this author

E-mail guy.cornelis@unibas.ch; Tel. secretary (+41) 61 267 21 21; Tel. direct (+41) 61 267 21 10; Fax (+41) 61 267 21 18.

Summary

YscV (FlhA in the flagellum) is an essential component of the inner membrane (IM) export apparatus of the type III secretion injectisome. It contains eight transmembrane helices and a large C-terminal cytosolic domain. YscV was expressed at a significantly higher level than the other export apparatus components YscR, YscS, YscT, and YscU, and YscV-EGFP formed bright fluorescent spots at the bacterial periphery, colocalizing in most cases with YscC-mCherry. This suggested that YscV is the only protein of the export apparatus that oligomerizes. Oligomerization required the cytosolic domain of YscV, as well as YscR, -S, -T, but no other Ysc protein, indicating that an IM platform can assemble independently from the membrane-ring forming proteins YscC, -D, -J. However, in the absence of YscC, -D, -J, this IM platform moved laterally at the bacterial surface. YscJ, but not YscD could be recruited to the IM platform in the absence of the secretin YscC. As YscJ was shown earlier to be also recruited by the outer membrane (OM) platform made of YscC and YscD, we infer that assembly of the injectisome proceeds through the independent assembly of an IM and an OM platform that merge through YscJ.

Ancillary