Structural similarity of secretins from type II and type III secretion systems - PubMed (original) (raw)

. 2014 Sep 2;22(9):1348-1355.

doi: 10.1016/j.str.2014.07.005. Epub 2014 Aug 21.

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Structural similarity of secretins from type II and type III secretion systems

Tommaso Tosi et al. Structure. 2014.

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Abstract

Secretins, the outer membrane components of several secretion systems in Gram-negative bacteria, assemble into channels that allow exoproteins to traverse the membrane. The membrane-inserted, multimeric regions of PscC, the Pseudomonas aeruginosa type III secretion system secretin, and PulD, the Klebsiella oxytoca type II secretion system secretin, were purified after cell-free synthesis and their structures analyzed by single particle cryoelectron microscopy. Both homomultimeric, barrel-like structures display a "cup and saucer" architecture. The "saucer" region of both secretins is composed of two distinct rings, with that of PulD being less segmented than that of PscC. Both secretins have a central chamber that is occluded by a plug linked to the chamber walls through hairpin-like structures. Comparisons with published structures from other bacterial systems reveal that secretins have regions of local structural flexibility, probably reflecting their evolved functions in protein secretion and needle assembly.

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