Mereghetti Paolo, Wade Rebecca C
Heidelberg Institute for Theoretical Studies (HITS) gGmbH, Schloß-Wolfsbrunnenweg 35, 69118 Heidelberg, Germany.
BMC Biophys. 2011 Apr 21;4:9. doi: 10.1186/2046-1682-4-9.
Hydrophobins are small proteins produced by filamentous fungi that have a variety of biological functions including coating of spores and surface adhesion. To accomplish these functions, they rely on unique interface-binding properties. Using atomic-detail implicit solvent rigid-body Brownian dynamics simulations, we studied the diffusion of HFBI, a class II hydrophobin from Trichoderma reesei, in aqueous solution in the presence and absence of a graphite surface.
In the simulations, HFBI exists in solution as a mixture of monomers in equilibrium with different types of oligomers. The oligomerization state depends on the conformation of HFBI. When a Highly Ordered Pyrolytic Graphite (HOPG) layer is present in the simulated system, HFBI tends to interact with the HOPG layer through a hydrophobic patch on the protein.
From the simulations of HFBI solutions, we identify a tetrameric encounter complex stabilized by non-polar interactions between the aliphatic residues in the hydrophobic patch on HFBI. After the formation of the encounter complex, a local structural rearrangement at the protein interfaces is required to obtain the tetrameric arrangement seen in HFBI crystals. Simulations performed with the graphite surface show that, due to a combination of a geometric hindrance and the interaction of the aliphatic sidechains with the graphite layer, HFBI proteins tend to accumulate close to the hydrophobic surface.
疏水蛋白是丝状真菌产生的小蛋白质，具有多种生物学功能，包括孢子包被和表面粘附。为实现这些功能，它们依赖独特的界面结合特性。我们使用原子细节隐式溶剂刚体布朗动力学模拟，研究了来自里氏木霉的II类疏水蛋白HFBI在有无石墨表面存在的情况下在水溶液中的扩散。
在模拟中，HFBI以单体与不同类型寡聚体处于平衡的混合物形式存在于溶液中。寡聚化状态取决于HFBI的构象。当模拟系统中存在高度有序热解石墨（HOPG）层时，HFBI倾向于通过蛋白质上的疏水区域与HOPG层相互作用。
通过对HFBI溶液的模拟，我们确定了一种由HFBI疏水区域中脂肪族残基之间的非极性相互作用稳定的四聚体相遇复合物。相遇复合物形成后，需要在蛋白质界面进行局部结构重排以获得HFBI晶体中所见的四聚体排列。在有石墨表面的情况下进行的模拟表明，由于几何位阻以及脂肪族侧链与石墨层的相互作用，HFBI蛋白倾向于在疏水表面附近聚集。
