Strunk, Timo; Hamacher, Kay; Hoffgaard, Franziska; Engelhardt, Harald; Zillig, Martina Daniela; Faist, Karin; Wenzel, Wolfgang; Pfeifer, Felicitas
Structural model of the gas vesicle protein GvpA and analysis of GvpA mutants in vivo
MOLECULAR MICROBIOLOGY, 81:56-68, JUL 2011

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-alpha-beta-beta-alpha-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 beta-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 a-helix I and alpha-helix II, but also in the beta-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.

DOI:10.1111/j.1365-2958.2011.07669.x

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