3.A.5.1.1
General secretory pathway (Sec-SRP) complex.  A biphasic pulling force may act on TMSs during translocon-mediated membrane integration (Ismail et al. 2012).  Intermediate structures for the insertion of integral membrane proteins have been visualized (Bischoff et al. 2014).  Insertion of the Type II single span (N-terminus, in, C-terminus, out) protein, RodZ, requires only SecYEG, SecA and the pmf, but not SecB, SecDF, YidC or FtsY (Rawat et al. 2015).  The combined effects of ribosome and peptide binding to SecYEG may allow for co-translational membrane insertion of successive transmembrane segments (Ge et al. 2014). SecA penetrates deeply into the SecYEG channel during insertion, contacting transmembrane helices and periplasmic loops (Banerjee et al. 2017). A partially inserted nascent chain unzips the Sec translocon's lateral gate (Kater et al. 2019). Cardiolipin (CL) is required in vivo for the stability of the bacterial translocon (SecYEG) as well as its efficient function in co-translational insertion into and translocation across the inner membrane of E. coli (Ryabichko et al. 2020). PpiD (623 aas and 1 N-terminal TMS), a peptidyl-prolyl cis-trans isomerase D, and YfgM (206 aas and 1 N-terminal TMS) facilitate the transport of toxins into the E. coli cell in a SecY-dependent process (Jones et al. 2021). Synchronized real-time measurement of Sec-mediated protein translocation has been described (Gupta et al. 2021). An extracellular cutinase from Amycolatopsis mediterranei (AmCut) is able to degrade the plastics, polycaprolactone and polybutylene succinate (Tan et al. 2022). It is secreted from E. coli using the Sec system for export across the inner membrane, and possibly, a non-classical secretion pathway for export across the outer membrane (Tan et al. 2022). The inner membrane YfgM-PpiD heterodimer, both proteins with N-terminal transmembrane segments and C-terminal periplasmic domains, acts as a functional unit that associates with the SecY/E/G translocon and promotes protein translocation (Miyazaki et al. 2022). Helicobacter pylori SecA Inhibitors have been identified (Jian et al. 2023).

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