Structural Dynamics of the Functional Nonameric Type III Translocase Export Gate

Structural and Functional Analysis of SsaV Cytoplasmic Domain and Variable Linker States in the Context of the InvA-SsaV Chimeric Protein

“…However, we were unable to obtain a stably-assembled InvA sample for the cryo-EM structural study, even after several rounds of high-throughput detergent screening. It has been shown that SctV C makes a significant contribution in maintaining the SctV nonamer ( 46 ). Previous structural studies suggested that InvA C tends to be a monomer in solution ( 51 ).…”

“…However, SctV was missing in all these trials, even though all other export apparatus components could be captured; this suggests a loose interaction between SctV and other components of the export apparatus and the basal body. The structure of SctV C has been identified as a homo-nonamer through crystal and cryo-electron microscopy (cryo-EM) structural studies, and the intermolecular polar interactions between monomers are thought to be the leading force maintaining the SctV C oligomeric state ( 26 , 44 – 46 ). Recently, an in situ cryo-electron tomography (cryo-ET) study identified the location of InvA in the bacterial inner membrane and showed a high-order oligomeric state of the TM domain of InvA ( 12 ).…”

TypeIIIsecretion byYersinia pseudotuberculosisis reliant upon an authentic N‐terminalYscXsecretor domain

“…Thus, it is utterly intriguing that the Ysc‐T3SS clade has evolved a unique system in YscX–YscY‐SctV for coordinating early substrate secretion. Several structural studies have proposed a conserved region in the cytoplasmic domain of SctV that is thought to recognize a chaperone‐substrate complex and prepare substrates for secretion (Erhardt et al, 2017; Kuhlen et al, 2021; Majewski et al, 2020; Matthews‐Palmer et al, 2021; Xing et al, 2018; Yuan et al, 2021). Hence, SctV has a conserved universal role in all T3SSs, although bacteria producing the Ysc‐T3SS clade seems to have customized this function in a way that relies on the YscX–YscY complex.…”

Virulence-associated type III secretion systems in Gram-negative bacteria

“…The cytoplasmic domain forms a nonameric ring with a pore size of 50 Å [9,[20][21][22]. It is postulated to serve as a docking platform for substrates and chaperones and to be involved in the specificity switching of secretion [9,23,24].…”

“…It is difficult to match these different figures, questioning the relevance of this targeting hypothesis. Moreover, it was observed that chaperone-substrate pairs were capable of binding SctN and SctV [24,50,54,138,139]. It is not understood whether these interactions required a previous interaction with the SctKQL complex (multi-step targeting) or occur directly (one-step targeting).…”