Estimated number of proteins associated with protein transport

Range Table - link
Organism Bacteria Escherichia coli
Reference Kudva R, Denks K, Kuhn P, Vogt A, Müller M, Koch HG. Protein translocation across the inner membrane of Gram-negative bacteria: the Sec and Tat dependent protein transport pathways. Res Microbiol. 2013 Jul-Aug164(6):505-34. doi: 10.1016/j.resmic.2013.03.016 p.514 table 2PubMed ID23567322
Primary Source See refs beneath table
Comments P.513 right column bottom paragraph: "GTP hydrolysis leads to the dissociation of the two proteins and binding of the ribosome-nascent chain complex to the SecYEG translocon (Miller et al., 1994, Grudnik et al., 2009). Due to the limited number of SecYEG translocons in E. coli (Table 2, Drew et al., 2003), only approx. 5% of all FtsY molecules can be in contact with SecY, while the majority are bound to the negatively charged phospholipid surface of the membrane." P.524 right column 3rd paragraph: "An interesting and yet puzzling issue has developed recently from data showing that many multi-spanning membrane proteins can be delivered by SRP [signal recognition particle] to either SecYEG or YidC for insertion (Welte et al., 2012). As the concentration of YidC exceeds that of SecYEG (Table 2), membrane protein insertion via YidC may be more prevalent than previously anticipated. This would also explain why the limited number of SecYEG molecules is sufficient for handling both secretory proteins and a sub-set of inner membrane proteins. However, the mechanism of dual targeting of substrates to either SecYEG or YidC has to be confirmed in live cells." See note above table
Entered by Uri M
ID 113764