Solution structure of the TatB component of the twin-arginine translocation system.
The twin-arginine protein transport (Tat) system translocates fully folded proteins across lipid membranes. In Escherichia coli, the Tat system comprises three essential components: TatA, TatB and TatC. The protein translocation process is proposed to initiate by signal peptide recognition and substrate binding to the TatBC complex. Upon formation of the TatBC-substrate protein complex, the TatA subunits are recruited and form the protein translocation pore. Experimental evidences suggest that TatB forms a tight complex with TatC at 1:1 molar ratio and the TatBC complex contains multiple copies of both proteins. Cross-linking experiments demonstrate that TatB functions in tetrameric units and interacts with both TatC and substrate proteins. However, structural information of the TatB protein is still lacking, and its functional mechanism remains elusive. Herein, we report the solution structure of TatB in DPC micelles determined by Nuclear Magnetic Resonance (NMR) spectroscopy. Overall, the structure shows an extended 'L-shape' conformation comprising four helices: a transmembrane helix (TMH) α1, an amphipathic helix (APH) α2, and two solvent exposed helices α3 and α4. The packing of TMH and APH is relatively rigid, whereas helices α3 and α4 display notably higher mobility. The observed floppiness of helices α3 and α4 allows TatB to sample a large conformational space, thus providing high structural plasticity to interact with substrate proteins of different sizes and shapes.
Beijing Nuclear Magnetic Resonance Center, Peking University, Beijing 100871, China; College of Life Sciences, Peking University, Beijing 100871, China.
Yi
Y
Zhang
Beijing Nuclear Magnetic Resonance Center, Peking University, Beijing 100871, China; College of Life Sciences, Peking University, Beijing 100871, China.
Lei
L
Wang
Beijing Nuclear Magnetic Resonance Center, Peking University, Beijing 100871, China; College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China. Electronic address: yunfei@pku.edu.cn.
Yunfei
Y
Hu
Beijing Nuclear Magnetic Resonance Center, Peking University, Beijing 100871, China; College of Life Sciences, Peking University, Beijing 100871, China; College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China. Electronic address: changwen@pku.edu.cn.
Changwen
C
Jin
D000595:Amino Acid Sequence; D001120:Arginine; D002462:Cell Membrane / Q000737:chemistry; D004926:Escherichia coli / Q000737:chemistry / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry*; D026901:Membrane Transport Proteins / Q000737:chemistry*; D008823:Micelles; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017510:Protein Folding; D021382:Protein Sorting Signals; D017433:Protein Structure, Secondary; D021381:Protein Transport; D016415:Sequence Alignment; D012996:Solutions
D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D008823:Micelles; D021382:Protein Sorting Signals; D012996:Solutions; C473116:TatB protein, E coli; D001120:Arginine
Membrane protein; NMR; Protein dynamics; Protein structure; Protein transport; Twin-arginine translocation (Tat)