The structure and mechanism of the bacterial type II secretion system

Abstract

The T2SS is a macromolecular complex that spans the cell envelope of many Gram-negative bacteria. It is part of a much larger superfamily of type IV filament containing systems all of which share homologous components and conserved mechanistic principles. These include the type 4a and 4b pilus (Craig et al., 2019), tight adherence (Tad) pilus (Tomich et al., 2007), mannose-sensitive hemagglutinin pilus (Marsh and Taylor, 1999), competence pilus (Piepenbrink, 2019) and archaeal T4 pilus and flagellum (Makarova et al., 2016). These systems are ancient and fundamental to both bacterial and archaeal kingdoms with phylogeny analyses suggesting a lineage split from within the last universal common ancestor (LUCA) (Denise et al., 2019). The T2SS is particularly concentrated in the Alpha-, Beta-, Gamma-and Delta-proteobacteria, as well as the Bacteroidetes and Deferribacteres (Denise et al., 2019).

Budowa i znaczenie II systemu sekrecji białek w ekologii i patogenezie Legionella pneumophila

“…sekretyna -białka OM, które oligomeryzują, tworząc pory wydzielnicze) [4,31]. Sekretyna złożona jest z czterech N-końcowych domen peryplazmatycznych (N0, N1, N2 i N3), rdzenia oraz C-końcowej domeny S [32]. Zakotwiczony w błonie wewnętrznej (IM) kompleks składający się z białek T2S F, -L oraz -M tworzy obejmujący peryplazmę kanał, powstały na skutek oddziaływania z sekretyną.…”

CryoEM structure of the outer membrane secretin channel pIV from the f1 filamentous bacteriophage

“…Reports of stoichiometry range between twelve and fifteen monomers per complex, divided into a number of different domains. The C-terminal domain integrates into the bacterial outer membrane and forms a double-walled ß-barrel with a central gate forming a stricture at the centre 21 . Varying numbers of soluble N-domains connect to the ß-barrel and project into the periplasm.…”

“…The C-terminal domain integrates into the bacterial outer membrane and forms a doublewalled ß-barrel with a central gate forming a stricture at the centre 17 . Varying numbers of soluble N-domains connect to the ß-barrel and project into the periplasm.…”

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Secretin channel-interactors prevent antibiotic influx during type IV pili assembly in Pseudomonas aeruginosa

“…Cryo-electron microscopy (cryo-EM) of the secretin complexes revealed that these proteins share a similar architecture. A less-conserved N-terminal domain forms a periplasmic vestibule that interacts with the IM components of the virulence system, and a well-conserved C-terminal domain forms an OM channel with one or two gate structures (Weaver et al, 2020;Hu et al, 2018;D'Imprima et al, 2017;Naskar et al, 2021). Although secretin channels form much larger pore structures than the channels formed by a single polypeptide, it has been assumed that the gate structures of secretins prevent leakage of periplasmic contents and permeation of extracellular chemicals when they are not in use for protein secretion or pilus assembly (Majewski et al, 2018;Korotkov et al, 2011).…”