Podocytes are crucial cells of the glomerular filtration unit and playing a vital role at the interface of the blood-urine barrier. Podocyte slit-diaphragm is a modified tight junction that facilitates size and shape-dependent permselectivity. Several proteins including podocin, nephrin, CD2AP, and TRPC6 form a macromolecular assembly and constitute the slit-diaphragm. Podocin is an integral membrane protein attached to the inner membrane of the podocyte via a short transmembrane region (101-125). The cytosolic N- and C-terminus help podocin to attain a hook-like structure. Podocin shares 44% homology with stomatin family proteins and similar to the stomatin proteins, podocin was shown to associate into higher-order oligomers at the site of slit-diaphragm. However, the stoichiometry of the homo-oligomers and how it partakes in the macromolecular assemblies with other slit-diaphragm proteins remains elusive. Here we investigated the oligomeric propensity of a truncated podocin construct (residues:126-350). We show that the podocin domain majorly homo-oligomerize into a 16mer. Circular dichroism and fluorescence spectroscopy suggest that the 16mer oligomer has considerable secondary structure and moderate tertiary packing.

中文翻译：

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人Podocin结构域的结构特征和寡聚性质

足细胞是肾小球滤过单元的关键细胞，在血尿屏障的界面上起着至关重要的作用。足细胞裂-膜是一种改良的紧密连接，可促进大小和形状相关的渗透选择性。包括Podocin，nephrin，CD2AP和TRPC6在内的几种蛋白质形成了大分子装配体，并构成了横slit膜片。Podocin是通过短跨膜区域（101-125）附着在足细胞内膜上的不可或缺的膜蛋白。胞质的N和C端有助于Podocin获得钩状结构。Podocin与Stomatin家族蛋白具有44％的同源性，并且与Stomatin蛋白相似，Podocin被证明在裂膜的部位与高阶寡聚物缔合。然而，均聚物的化学计量以及它如何与其他裂膜片蛋白质一起参与大分子组装仍然难以捉摸。在这里，我们研究了截短的podocin构建体的寡聚倾向（残基：126-350）。我们显示，podocin域主要是同源齐聚成16mer。圆二色性和荧光光谱表明16聚体低聚物具有相当大的二级结构和中等的三级堆积。