Structural model of the gas vesicle protein GvpA and analysis of GvpA mutants in vivo |
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Authors: | Strunk Timo Hamacher Kay Hoffgaard Franziska Engelhardt Harald Zillig Martina Daniela Faist Karin Wenzel Wolfgang Pfeifer Felicitas |
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Affiliation: | Institute for Nanotechnology, Karlsruhe Institute of Technology, PO Box 3640, D-76021 Karlsruhe, Germany. |
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Abstract: | Gas vesicles are gas-filled protein structures increasing the buoyancy of cells. The gas vesicle envelope is mainly constituted by the 8 kDa protein GvpA forming a wall with a water excluding inner surface. A structure of GvpA is not available; recent solid-state NMR results suggest a coil-α-β-β-α-coil fold. We obtained a first structural model of GvpA by high-performance de novo modelling. Attenuated total reflection (ATR)-Fourier transform infrared spectroscopy (FTIR) supported this structure. A dimer of GvpA was derived that could explain the formation of the protein monolayer in the gas vesicle wall. The hydrophobic inner surface is mainly constituted by anti-parallel β-strands. The proposed structure allows the pinpointing of contact sites that were mutated and tested for the ability to form gas vesicles in haloarchaea. Mutations in α-helix I and α-helix II, but also in the β-turn affected the gas vesicle formation, whereas other alterations had no effect. All mutants supported the structural features deduced from the model. The proposed GvpA dimers allow the formation of a monolayer protein wall, also consistent with protease treatments of isolated gas vesicles. |
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