Our previous calculations of ionic interactions indicated that the Caenorhabditis elegans intermediate filament (IF) IFA proteins, in addition to IFA/IFB-1 heterodimers, may also form homodimers. In order to prove the significance of these calculations, we analysed the dimerization potential of the IFA chains in blot overlays. Unexpectedly, we found here that the dimerization of the IFA-1 protein was of both homotypic and heterotypic nature, and involved all proteins immobilized on the membrane (IFA-1, IFA-2, IFA-4, IFB-1, IFB-2, IFC-1, IFC-2, IFD-1, IFD-2 and IFP-1). A similar interaction profile, though less complex, was observed for two biotinylated proteins (IFA-2 and IFA-4). These and previous results indicate that the IFA proteins are able to form many different heteropolymeric and homopolymeric complexes in the C. elegans tissue, but that only those triggered by the IFA-specific IFB-1 protein result in mature IFs. Moreover, the calculations of the possible ionic interactions between the individual rod sequences as well as their various deletion variants indicated a special role in this process for the middle part of the C. elegans IF coil 1B segment that is deleted in all vertebrate cytoplasmic IFs. We hypothesized here, therefore, that the striking promiscuity of the C. elegans IFs originally involved a nuclear lamin which, due to a two-heptad-long rod deletion, prevented formation of a functional lamin/cIF dimer. This, in concert with an efficient dimerization and a strict tissue-specific co-expression, may allow expansion and maintenance of the multiple Caenorhabditis IFs. A possible implication for evolution of chordate IFs proteins is also discussed.

中文翻译：

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秀丽隐杆线虫IF蛋白之间的混杂二聚化和解释多个IF如何在进化时间内持续存在的假说。

我们以前的离子相互作用计算表明，秀丽隐杆线虫中间丝（IF）IFA蛋白除IFA / IFB-1异二聚体外，还可能形成同型二聚体。为了证明这些计算的重要性，我们分析了印迹重叠中IFA链的二聚化潜力。出乎意料的是，我们在这里发现IFA-1蛋白的二聚化具有同型和异型性质，并且涉及固定在膜上的所有蛋白（IFA-1，IFA-2，IFA-4，IFB-1，IFB-2 ，IFC-1，IFC-2，IFD-1，IFD-2和IFP-1）。对于两种生物素化的蛋白质（IFA-2和IFA-4），观察到了相似的相互作用谱，尽管复杂程度较低。这些结果和先前的结果表明，IFA蛋白能够在秀丽隐杆线虫组织中形成许多不同的杂聚合和均聚合复合物，但是只有那些由IFA特定的IFB-1蛋白触发的蛋白才会导致成熟的IF。此外，对单个杆序列及其各种缺失变体之间可能的离子相互作用的计算表明，对于秀丽隐杆线虫IF线圈1B段的中间部分，在所有脊椎动物细胞质IFs中均被删除，在该过程中具有特殊作用。因此，我们在这里假设，秀丽隐杆线虫IFs的惊人混杂性最初涉及核纤层蛋白，由于两七长的棒缺失，阻止了功能性lamin / cIF二聚体的形成。这与有效的二聚化和严格的组织特异性共表达相结合，可允许扩展和维持多种秀丽隐杆线虫IF。还讨论了可能对含氟IFs蛋白的进化的影响。