T3SS_needle_E is a family of proteins from the operon that builds and controls the needle of the injection system of type III secretion. The YscE protein, produced by the pathogen Yersinia, assumes a secondary structure composed of two anti-parallel alpha-helices separated by a flexible loop [1]. The family is cytoplasmic and may help to stabilise and prevent early polymerisation of the needle-protein F [2,3].

1: The PscE-PscF-PscG complex controls type III secretion needle biogenesis in Pseudomonas aeruginosa. Quinaud M, Chabert J, Faudry E, Neumann E, Lemaire D, Pastor A, Elsen S, Dessen A, Attree I; J Biol Chem. 2005;280:36293-36300. PMID:16115870

2: Structural characterization of the Yersinia pestis type III secretion system needle protein YscF in complex with its heterodimeric chaperone YscE/YscG. Sun P, Tropea JE, Austin BP, Cherry S, Waugh DS; J Mol Biol. 2008;377:819-830. PMID:18281060

3: The Pseudomonas aeruginosa type III secretion system has an exotoxin S/T/Y independent pathogenic role during acute lung infection. Galle M, Jin S, Bogaert P, Haegman M, Vandenabeele P, Beyaert R; PLoS One. 2012;7:e41547. PMID:22844497