Architecture of the major component of the type III secretion system export apparatus

Patrizia Abrusci, Marta Vergara-Irigaray, Steven Johnson, Morgan D. Beeby, David R. Hendrixson, Pietro Roversi, Miriam E. Friede, Janet E. Deane, Grant J. Jensen, Christoph M. Tang, Susan M. Lea

Research output: Contribution to journalArticlepeer-review

163 Scopus citations


Type III secretion systems (T3SSs) are bacterial membrane-embedded nanomachines designed to export specifically targeted proteins from the bacterial cytoplasm. Secretion through T3SS is governed by a subset of inner membrane proteins termed the 'export apparatus'. We show that a key member of the Shigella flexneri export apparatus, MxiA, assembles into a ring essential for secretion in vivo. The ring-forming interfaces are well-conserved in both nonflagellar and flagellar homologs, implying that the ring is an evolutionarily conserved feature in these systems. Electron cryo-tomography revealed a T3SS-associated cytoplasmic torus of size and shape corresponding to those of the MxiA ring aligned to the secretion channel located between the secretion pore and the ATPase complex. This defines the molecular architecture of the dominant component of the export apparatus and allows us to propose a model for the molecular mechanisms controlling secretion.

Original languageEnglish (US)
Pages (from-to)99-104
Number of pages6
JournalNature Structural and Molecular Biology
Issue number1
StatePublished - Jan 2013

ASJC Scopus subject areas

  • Structural Biology
  • Molecular Biology


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