Schultz Jörg, Terhoeven Niklas
Department of Bioinformatics, Biocenter, University Würzburg, Am Hubland, Würzburg 97074, Germany.
BMC Res Notes. 2013 Sep 30;6:393. doi: 10.1186/1756-0500-6-393.
The actin cytoskeleton is essential for many physiological processes of eukaryotic cells. The emergence of new actin fibers is initiated by actin nucleators. Whereas most of them are evolutionary old, the cordon-bleu actin nucleator is classified as vertebrate specific.
Using sensitive methods for sequence similarity detection, we identified homologs of cordon-bleu not only in non-vertebrate chordates but also in arthropods, molluscs, annelids and platyhelminthes. These genes contain only a single WH2 domain and therefore resemble more the vertebrate cordon-bleu related 1 protein than the three WH2 domain containing cordon-bleu. Furthermore, we identified a homolog of the N-terminal, ubiquitin like, cobl domain of cordon-bleu in the cnidarian Nematostella vectensis.
Our results suggest that the ur-form of the cordon-bleu protein family evolved already with the emergence of the bilateria by the combination of existing cobl and WH2 domains. Following a vertebrate specific gene-duplication, one copy gained two additional WH2 domains leading to the actin nucleating cordon-bleu. The function of the ur-form of the cordon-bleu protein family is so far unknown. The identification of a homolog in the model organism Drosophila melanogaster could facilitate its experimental characterization.
肌动蛋白细胞骨架对于真核细胞的许多生理过程至关重要。新的肌动蛋白纤维的出现由肌动蛋白成核剂引发。虽然它们中的大多数在进化上较为古老，但蓝带肌动蛋白成核剂被归类为脊椎动物特有的。
使用敏感的序列相似性检测方法，我们不仅在非脊椎动物脊索动物中，还在节肢动物、软体动物、环节动物和扁形动物中鉴定出了蓝带的同源物。这些基因仅包含一个WH2结构域，因此与脊椎动物蓝带相关1蛋白更相似，而不是含有三个WH2结构域的蓝带。此外，我们在刺胞动物星状海葵中鉴定出了蓝带N端类似泛素的cobl结构域的同源物。
我们的结果表明，蓝带蛋白家族的原始形式在两侧对称动物出现时就已经通过现有cobl和WH2结构域的组合进化而来。在一次脊椎动物特有的基因复制之后，一个拷贝获得了另外两个WH2结构域，从而产生了肌动蛋白成核的蓝带。目前尚不清楚蓝带蛋白家族原始形式的功能。在模式生物黑腹果蝇中鉴定出同源物可能有助于对其进行实验表征。
