In vivo studies of the role of SecA during protein export in Escherichia coli

Chun, Sang-Yearn; Randall, Linda L.

doi:10.1128/jb.176.14.4197-4203.1994

Cited by 39 publications

(36 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This has been interpreted to mean that no sorting factors are required for post-translational translocation, because as noted above, SecA must act at the membrane to effect translocation. Yet the fact that 50 -75% of cellular SecA is found in the cytosol (16,58) suggests that it does not function solely at the membrane. Instead, there may be two alternatives for secretory protein targeting to the translocon, one that occurs post-translationally and without any sorting factor assistance and one that is mediated cotranslationally by SecA.…”

Section: Discussionmentioning

confidence: 99%

“…Because 50 -75% of the SecA in the cell are found in the cytosol and are not membrane-bound (16,58), the total cellular concentration of SecA is apparently sufficient to allow it to function both in events at the membrane and in selecting RNCs and targeting them to the translocon. Another functional difference between SecA and mammalian SRP is that the latter targets both nascent secretory and membrane proteins to the endoplasmic reticulum translocon (57).…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Selective SecA Association with Signal Sequences in Ribosome-bound Nascent Chains

Karamyshev

Johnson

2005

Journal of Biological Chemistry

View full text Add to dashboard Cite

The role of SecA in selecting bacterial proteins for export was examined using a heterologous system that lacks endogenous SecA and other bacterial proteins. This approach allowed us to assess the interaction of SecA with ribosome-bound photoreactive nascent chains in the absence of trigger factor, SecB, Ffh (the bacterial protein component of the signal recognition particle), and the SecYEG translocon in the bacterial plasma membrane. In the absence of membranes, SecA photocross-linked efficiently to nascent translocation substrate OmpA in ribosome-nascent chain (RNC) complexes in an interaction that was independent of both ATP and SecB. However, no photocross-linking to a nascent membrane protein that is normally targeted by a signal recognition particle was observed. Modification of the signal sequence revealed that its affinity for SecA and Ffh varied inversely. Gel filtration showed that SecA binds tightly to both translating and non-translating ribosomes. When purified SecA⅐RNC complexes containing nascent OmpA were exposed to inner membrane vesicles lacking functional SecA, the nascent chains were successfully targeted to SecYEG translocons. However, purified RNCs lacking SecA were unable to target to the same membranes. Taken together, these data strongly suggest that cytosolic SecA participates in the selection of proteins for export by co-translationally binding to the signal sequences of non-membrane proteins and directing those nascent chains to the translocon.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Selective SecA Association with Signal Sequences in Ribosome-bound Nascent Chains

Karamyshev

Johnson

2005

Journal of Biological Chemistry

View full text Add to dashboard Cite

show abstract

“…SecA has been reported to interact with the precursor proteins (22,23,58). Additionally, soluble SecA/SecB complex has been detected in vivo and was shown to be involved in targeting precursor proteins to the membrane (59).…”

Section: A 48-kda Domain Is Constantly Embedded In the Membrane Regarmentioning

confidence: 99%

A Significant Fraction of Functional SecA Is Permanently Embedded in the Membrane

Chen

Tai

1996

Journal of Biological Chemistry

View full text Add to dashboard Cite

SecA has been suggested to cycle on and off the cytoplasmic membrane of Escherichia coli during protein translocation. We have reconstituted 35 S-SecA onto SecA-depleted membrane vesicles and followed the fate of the membrane-associated 35 S-SecA during protein translocation. Some 35 S-SecA was released from the membranes in a translocation-independent manner. However, a significant fraction of 35 S-SecA remained on the membranes even after incubation with excess SecA. This fraction of 35 S-SecA was shown to be integrated into the membrane and was active in protein translocation, indicating that SecA cycling on and off membrane is not required for protein translocation. Proteolysis experiments did not support the model of SecA insertion and deinsertion during protein translocation; instead, a major 48-kDa domain was found persistently embedded in the membrane regardless of translocation status. Thus, in addition to catalyzing ATP hydrolysis, certain domains of SecA probably play an important structural role in the translocation machinery, perhaps forming part of the protein-conducting channels.

show abstract

“…Preprotein translocase is a multimeric membrane protein complex that in addition to SecA consists of the integral membrane proteins SecY, SecE, and SecG as stable subunits (3)(4)(5), and SecD and SecF as accessory proteins (6,7). The dynamic distribution of SecA between the cytosol and the membrane is determined by the amount of integral translocase subunits present in the membrane and by growth conditions (8)(9)(10)(11). The heterotrimeric SecYEG complex constitutes a high-affinity membrane binding site for SecA (3,12), and the SecA bound at these sites exposes a carboxyterminal domain to the periplasmic face of the membrane (8).…”

mentioning

confidence: 99%

Inhibition of Preprotein Translocation and Reversion of the Membrane Inserted State of SecA by a Carboxyl Terminus Binding MAb

et al. 1997

View full text Add to dashboard Cite

Inhibition of preprotein translocation and reversion of the membrane inserted state of SecA by a carboxyl terminus binding MAb den Blaauwen, T; de Wit, J.G; Gosker, H.; van der Does, C.; Breukink, E.J.; de Leij, Lou; Driessen, A.J.M. Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum.

show abstract

In vivo studies of the role of SecA during protein export in Escherichia coli

Abstract: . Rev. Biochem. 60:101-124, 1991 With the aim of eventual elucidation of the role of ATP binding and hydrolysis in the export cycle, we compared the effects of treating a growing culture with sodium azide and the expression of an allele of SecA that has an altered ATPbinding site.

Cited by 39 publications

References 35 publications

Selective SecA Association with Signal Sequences in Ribosome-bound Nascent Chains

Selective SecA Association with Signal Sequences in Ribosome-bound Nascent Chains

A Significant Fraction of Functional SecA Is Permanently Embedded in the Membrane

Inhibition of Preprotein Translocation and Reversion of the Membrane Inserted State of SecA by a Carboxyl Terminus Binding MAb

Contact Info

Product

Resources

About