title: Structural basis for TatA oligomerization: an NMR study of Escherichia coli TatA dimeric structure.
abstract: Many proteins are transported across lipid membranes by protein translocation systems in living cells. The twin-arginine transport (Tat) system identified in bacteria and plant chloroplasts is a unique system that transports proteins across membranes in their fully-folded states. Up to date, the detailed molecular mechanism of this process remains largely unclear. The Escherichia coli Tat system consists of three essential transmembrane proteins: TatA, TatB and TatC. Among them, TatB and TatC form a tight complex and function in substrate recognition. The major component TatA contains a single transmembrane helix followed by an amphipathic helix, and is suggested to form the translocation pore via self-oligomerization. Since the TatA oligomer has to accommodate substrate proteins of various sizes and shapes, the process of its assembly stands essential for understanding the translocation mechanism. A structure model of TatA oligomer was recently proposed based on NMR and EPR observations, revealing contacts between the transmembrane helices from adjacent subunits. Herein we report the construction and stabilization of a dimeric TatA, as well as the structure determination by solution NMR spectroscopy. In addition to more extensive inter-subunit contacts between the transmembrane helices, we were also able to observe interactions between neighbouring amphipathic helices. The side-by-side packing of the amphipathic helices extends the solvent-exposed hydrophilic surface of the protein, which might be favourable for interactions with substrate proteins. The dimeric TatA structure offers more detailed information of TatA oligomeric interface and provides new insights on Tat translocation mechanism.
authors.affiliation: Beijing Nuclear Magnetic Resonance Center, Peking University, Beijing, China; College of Life Sciences, Peking University, Beijing, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Beijing Nuclear Magnetic Resonance Center, Peking University, Beijing, China; College of Life Sciences, Peking University, Beijing, China; College of Chemistry and Molecular Engineering, Peking University, Beijing, China.
authors.forename: Yunfei
authors.initials: Y
authors.lastname: Hu
authors.affiliation: Beijing Nuclear Magnetic Resonance Center, Peking University, Beijing, China; College of Chemistry and Molecular Engineering, Peking University, Beijing, China.
authors.forename: Hongwei
authors.initials: H
authors.lastname: Li
authors.affiliation: Beijing Nuclear Magnetic Resonance Center, Peking University, Beijing, China; College of Life Sciences, Peking University, Beijing, China; College of Chemistry and Molecular Engineering, Peking University, Beijing, China; Beijing National Laboratory for Molecular Sciences, Peking University, Beijing, China.
authors.forename: Changwen
authors.initials: C
authors.lastname: Jin
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism*; D057927:Hydrophobic and Hydrophilic Interactions; D009682:Magnetic Resonance Spectroscopy; D026901:Membrane Transport Proteins / Q000737:chemistry* / Q000378:metabolism*; D008823:Micelles; D055503:Protein Multimerization; D055550:Protein Stability; D017433:Protein Structure, Secondary; D012996:Solutions
chemical_list: D000596:Amino Acids; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D008823:Micelles; D012996:Solutions; C499697:TatA protein, E coli
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