A potential late stage intermediate of twin-arginine dependent protein translocation in Escherichia coli
- authored by
- Hendrik Geise, Eyleen Sabine Heidrich, Christoph Stefan Nikolin, Denise Mehner-Breitfeld, Thomas Brüser
- Abstract
The twin-arginine translocation (Tat) system transports folded proteins across membranes of prokaryotes, plant plastids, and some mitochondria. According to blue-native polyacrylamide gel electrophoresis after solubilization with digitonin, distinct interactions between the components TatA, TatB, and TatC result in two major TatBC-containing complexes in Escherichia coli that can bind protein substrates. We now report the first detection of a TatABC complex that likely represents the state at which transport occurs. This complex was initially found when the photo cross-linking amino acid p-benzoyl-L-phenylalanine (Bpa) was introduced at position I50 on the periplasmic side of the first trans-membrane domain of TatC. Cross-linking of TatCI50Bpa resulted in TatC-TatC-cross-links, indicating a close proximity to neighboring TatC in the complex. However, the new complex was not caused by cross-links but rather by non-covalent side chain interactions, as it was also detectable without UV-cross-linking or with an I50Y exchange. The new complex did not contain any detectable substrate. It was slightly upshifted relative to previously reported substrate-containing TatABC complexes. In the absence of TatA, an inactive TatBCI50Bpa complex was formed of the size of wild-type substrate-containing TatABC complexes, suggesting that TatB occupies TatA-binding sites at TatCI50Bpa. When substrate binding was abolished by point mutations, this TatBCI50Bpa complex shifted analogously to active TatABCI50Bpa complexes, indicating that a defect substrate-binding site further enhances TatB association to TatA-binding sites. Only TatA could shift the complex with an intact substrate-binding site, which explains the TatA requirement for substrate transport by TatABC systems.
- Organisation(s)
-
Institute of Microbiology
- Type
- Article
- Journal
- Frontiers in Microbiology
- Volume
- 10
- ISSN
- 1664-302X
- Publication date
- 07.2019
- Publication status
- Published
- Peer reviewed
- Yes
- ASJC Scopus subject areas
- Microbiology, Microbiology (medical)
- Electronic version(s)
-
https://doi.org/10.3389/fmicb.2019.01482 (Access:
Open)
https://doi.org/10.15488/5218 (Access: Open)
