Institute for Nanotechnology, Karlsruhe Institute of Technology, PO Box 3640, D-76021 Karlsruhe, Germany.
Mol Microbiol. 2011 Jul;81(1):56-68. doi: 10.1111/j.1365-2958.2011.07669.x. Epub 2011 May 27.
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.
气室是充满气体的蛋白质结构，可增加细胞的浮力。气室包膜主要由 8 kDa 蛋白 GvpA 组成，形成具有排斥水的内表面的壁。目前还没有 GvpA 的结构；最近的固态 NMR 结果表明它具有螺旋-α-β-β-α-螺旋折叠。我们通过高性能从头建模获得了 GvpA 的第一个结构模型。衰减全反射（ATR）-傅里叶变换红外光谱（FTIR）支持该结构。推导了 GvpA 的二聚体，它可以解释气室壁中蛋白质单层的形成。疏水性的内表面主要由反平行的β-折叠组成。所提出的结构可以确定突变的接触位点，并测试其在盐杆菌中形成气室的能力。α-螺旋 I 和 α-螺旋 II 中的突变，以及β-转角中的突变，都会影响气室的形成，而其他改变则没有影响。所有的突变体都支持从模型中推断出的结构特征。所提出的 GvpA 二聚体允许形成单层蛋白质壁，这也与分离气室的蛋白酶处理一致。
