Multipart Chaperone-Effector Recognition in the Type III Secretion System of Chlamydia trachomatis

Abstract

Background:The type III secretion (T3S) chaperone Scc4 modulates Chlamydia RNA polymerase holoenzyme activity and is also required for secretion of the gatekeeper CopN. Results: Interactions between the Scc4 and Scc1 chaperones and CopN are characterized. Conclusion: Scc4 forms a ternary complex with Scc1 and CopN to promote CopN secretion during infection. Significance: Scc4 is an important link between the T3S system and transcription.

Novel T3SS effector EseK in Edwardsiella piscicida is chaperoned by EscH and EscS to express virulence

“…(a) MBP pull-down assays using purified proteins MBP-EscS (full-length) and His sumo-EseK-His incubated with MBP beads. Chaperones usually bind effectors directly; therefore, understanding the dynamic interactions between T3SCs and their process (Shen et al, 2015). (b) Predicted αhelices of EscS.…”

“…Here, we show that T3SS effector EseK has two class I chaperones that we Unlike many other class I T3SCs that share a common secondary structure fold that is characterised by an α-β-β-β-α-β-β-α topology (e.g.,YopE, SptP, CesT, SrcA, SicP, and SycE) (Birtalan, Phillips, & Ghosh, 2002;Brinkworth et al, 2011;Cooper et al, 2010), EscH and EscS have predicted secondary structure topologies of α-β-β-β-β-α and α-α-α, respectively, representing possible exceptions among class I chaperones. Chaperones usually bind effectors directly; therefore, understanding the dynamic interactions between T3SCs and their binding partners is a necessary step in elucidating the regulated T3SS process (Shen et al, 2015). Despite the high degree of structural and functional conservation among chaperones, only a few chaperones have had their binding domains mapped to understand their interactions with their subjects.…”

“…Class I T3SCs can bind T3SS effectors directly. Class IA T3SCs, such as SicP (Button & Galán, 2011), SycE (Rodgers, Gamez, Riek, & Ghosh, 2008), and CesT (Thomas et al, 2005), bind a single effector and are often encoded by a gene adjacent to an effector gene (Locher et al, 2005).Whereas class IB T3SCs, such as Spa15 (van Eerde, Hamiaux, Perez, Parsot, & Dijkstra, 2004) and Mcsc (Spaeth, Chen, & Valdivia, 2009), bind multiple effectors and are often encoded in an operon that carries genes encoding components of T3SS secretion apparatus (Locher et al, 2005;Shen et al, 2015). Class III T3SCs (CdsE and CdsG; Betts, Twiggs, Sal, Wyrick, & Fields, 2008) bind needle and filament proteins, and they are thought to prevent premature association or polymerisation of monomeric needle and filament proteins within the bacterial cytoplasm.…”

Chlamydia cell biology and pathogenesis

“…Late genes are regulated either by a stage-specific sigma factor (σ 28 ) 19 or through the relief of transcriptional repression of σ 66 -dependent promoters by the repressor early upstream open reading frame (EUO) 19,23 . Transcriptional regulation is also coupled to the T3SS 24–26 . Much of this insight comes from in vitro studies; advances in chlamydial genetics (BOX 2) will enable the analysis of current models in vivo .…”

Potency of Solithromycin against Fast- and Slow-Growing Chlamydial Organisms

“…Sol-mediated suppression of the T3S system has also been reported in enterohemorrhagic Escherichia coli strains (29). The precise details of the T3S process remain unclear in C. trachomatis, but they are developmentally regulated (30)(31)(32), and EBs have the assembled T3S apparatus (33). Our data, indicating that Sol does not prevent EBs from infection, suggest that direct blockage of the T3S apparatus in EBs is unlikely the main mechanism for Sol-induced T3S perturbation.…”