GspD is a type II general secretion pathway protein involved in protein export. This is the N0 domain found at the N-terminal of GspD type II secretins and its close homologues [1-5]. These proteins form a dodecameric ring, in which the N0 domain mediate extensive contacts suggesting that dodecameric N0 ring is an important feature of T2SS secretins [4]. This domain is also found in virion export proteins, proteins thought to form a channel across the host outer membrane for the purposes of extruding the bacteriophage.

1: Crystal structure of the N-terminal domain of the secretin GspD from ETEC determined with the assistance of a nanobody. Korotkov KV, Pardon E, Steyaert J, Hol WG; Structure. 2009;17:255-265. PMID:19217396

2: Structural and functional studies on the interaction of GspC and GspD in the type II secretion system. Korotkov KV, Johnson TL, Jobling MG, Pruneda J, Pardon E, Heroux A, Turley S, Steyaert J, Holmes RK, Sandkvist M, Hol WG; PLoS Pathog. 2011;7:e1002228. PMID:21931548

3: New insights into the assembly of bacterial secretins: structural studies of the periplasmic domain of XcpQ from Pseudomonas aeruginosa. Van der Meeren R, Wen Y, Van Gelder P, Tommassen J, Devreese B, Savvides SN; J Biol Chem. 2013;288:1214-1225. PMID:23188826

4: A dodecameric ring-like structure of the N0 domain of the type II secretin from enterotoxigenic Escherichia coli. Korotkov KV, Delarosa JR, Hol WGJ; J Struct Biol. 2013;183:354-362. PMID:23820381

5: Unraveling the Self-Assembly of the Pseudomonas aeruginosa XcpQ Secretin Periplasmic Domain Provides New Molecular Insights into Type II Secretion System Secreton Architecture and Dynamics. Douzi B, Trinh NTT, Michel-Souzy S, Desmyter A, Ball G, Barbier P, Kosta A, Durand E, Forest KT, Cambillau C, Roussel A, Voulhoux R; mBio. 2017; [Epub ahead of print] PMID:29042493