Litjens Sandy H M, Wilhelmsen Kevin, de Pereda José M, Perrakis Anastassis, Sonnenberg Arnoud
Divisions of Cell Biology, and Molecular Carcinogenesis, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands.
J Biol Chem. 2005 Jun 10;280(23):22270-7. doi: 10.1074/jbc.M411818200. Epub 2005 Apr 6.
The binding of plectin to the beta4 subunit of the alpha6beta4 integrin is a critical step in the formation of hemidesmosomes. An important interaction between these two proteins occurs between the actin-binding domain (ABD) of plectin and the first pair of fibronectin type III (FNIII) domains and a small part of the connecting segment of beta4. Previously, a few amino acids, critical for this interaction, were identified in both plectin and beta4 and mapped on the crystal structures of the ABD of plectin and the first pair of FNIII domains of beta4. In the present study, we used this biochemical information and protein-protein docking calculations to construct a model of the binary complex between these two protein domains. The top scoring computational model predicts that the calponin-homology 1 (CH1) domain of the ABD associates with the first and the second FNIII domains of beta4. Our mutational analysis of the residues at the proposed interface of both the FNIII and the CH1 domains is in agreement with the suggested interaction model. Computational simulations to predict protein motions suggest that the exact model of FNIII and plectin CH1 interaction might well differ in detail from the suggested model due to the conformational plasticity of the FNIII domains, which might lead to a closely related but different mode of interaction with the plectin-ABD. Furthermore, we show that Ser-1325 in the connecting segment of beta4 appears to be essential for the recruitment of plectin into hemidesmosomes in vivo. This is consistent with the proposed model and previously published mutational data. In conclusion, our data support a model in which the CH1 domain of the plectin-ABD associates with the groove between the two FNIII domains of beta4.
网蛋白与α6β4整合素的β4亚基结合是半桥粒形成的关键步骤。这两种蛋白质之间的重要相互作用发生在网蛋白的肌动蛋白结合结构域（ABD）与第一对纤连蛋白III型（FNIII）结构域以及β4连接段的一小部分之间。此前，已在网蛋白和β4中鉴定出对这种相互作用至关重要的几个氨基酸，并将其定位在网蛋白ABD和β4的第一对FNIII结构域的晶体结构上。在本研究中，我们利用这些生化信息和蛋白质-蛋白质对接计算构建了这两个蛋白质结构域之间二元复合物的模型。得分最高的计算模型预测，ABD的钙调蛋白同源性1（CH1）结构域与β4的第一和第二个FNIII结构域相关联。我们对FNIII和CH1结构域拟议界面处残基的突变分析与所提出的相互作用模型一致。预测蛋白质运动的计算模拟表明，由于FNIII结构域的构象可塑性，FNIII与网蛋白CH1相互作用的确切模型在细节上可能与所提出的模型有很大差异，这可能导致与网蛋白-ABD形成密切相关但不同的相互作用模式。此外，我们表明β4连接段中的Ser-1325似乎对于体内网蛋白募集到半桥粒中至关重要。这与所提出的模型和先前发表的突变数据一致。总之，我们的数据支持一种模型，即网蛋白-ABD的CH1结构域与β4的两个FNIII结构域之间的凹槽相关联。
