Conserved features in TamA enable interaction with TamB to drive the activity of the translocation and assembly module

• Published in: Scientific reports 2015-08, Vol.5 (1), p.12905-12905, Article 12905
• Main Authors: Selkrig, Joel, Belousoff, Matthew J., Headey, Stephen J., Heinz, Eva, Shiota, Takuya, Shen, Hsin-Hui, Beckham, Simone A., Bamert, Rebecca S., Phan, Minh-Duy, Schembri, Mark A., Wilce, Matthew C.J., Scanlon, Martin J., Strugnell, Richard A., Lithgow, Trevor
• Format: Article
• Language: English
• Subjects: 140/131; 631/326/41; 631/326/88; 631/337; 631/45/535/878/1263; 82; 82/29; Amino Acid Sequence; Bacterial Outer Membrane Proteins - chemistry; Bacterial Outer Membrane Proteins - physiology; Biosynthesis; Conserved Sequence; Docks; Evolution, Molecular; Humanities and Social Sciences; Lipids; Magnetic resonance spectroscopy; Membranes; Models, Molecular; Molecular Sequence Data; multidisciplinary; NMR; Nuclear magnetic resonance; Outer membranes; Periplasm; Protein Binding; Protein folding; Protein Interaction Domains and Motifs; Protein Structure, Quaternary; Protein Structure, Secondary; Proteins; Quartz crystal microbalance; Rigidity; Science; Spectroscopy; Translocation; Virulence; X-ray scattering
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/srep12905

The biogenesis of membranes from constituent proteins and lipids is a fundamental aspect of cell biology. In the case of proteins assembled into bacterial outer membranes, an overarching question concerns how the energy required for protein insertion and folding is accessed at this remote location of the cell. The translocation and assembly module (TAM) is a nanomachine that functions in outer membrane biogenesis and virulence in diverse bacterial pathogens. Here we demonstrate the interactions through which TamA and TamB subunits dock to bridge the periplasm and unite the outer membrane aspects to the inner membrane of the bacterial cell. We show that specific functional features in TamA have been conserved through evolution, including residues surrounding the lateral gate and an extensive surface of the POTRA domains. Analysis by nuclear magnetic resonance spectroscopy and small angle X-ray scattering document the characteristic structural features of these POTRA domains and demonstrate rigidity in solution. Quartz crystal microbalance measurements pinpoint which POTRA domain specifically docks the TamB subunit of the nanomachine. We speculate that the POTRA domain of TamA functions as a lever arm in order to drive the activity of the TAM, assembling proteins into bacterial outer membranes.