Type III Secretion: Building and Operating a Remarkable Nanomachine

Trends Biochem Sci. 2016 Feb;41(2):175-189. doi: 10.1016/j.tibs.2015.09.005. Epub 2015 Oct 28.


The Type III secretion system (T3SS) is a protein export pathway that is widespread in Gram-negative bacteria and delivers effector proteins directly into eukaryotic cells. At its core lie the injectisome (a sophisticated transmembrane secretion apparatus) and a complex network of specialized chaperones that target secretory proteins to the antechamber of the injectisome. The assembly of the system, and the subsequent secretion of proteins through it, undergo fine-tuned, hierarchical regulation. Here, we present the current understanding of the injectisome assembly process, secretion hierarchy, and the role of chaperones. We discuss these events in light of available structural and biochemical dissection and propose future directions essential to revealing mechanistic insight into this fascinating nanomachine.

Keywords: Type III secretion (T3S); Type III secretion system (T3SS); chaperones; energy requirements; injectisome assembly; secretion regulation.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Bacterial Proteins / metabolism
  • Gram-Negative Bacteria / metabolism*
  • Nanotechnology*


  • Bacterial Proteins