Buelt M K, Glidden B J, Storm D R
Department of Pharmacology, University of Washington, Seattle 98195.
J Biol Chem. 1994 Nov 25;269(47):29367-70.
Human p68 RNA helicase is a nuclear RNA-dependent ATPase that belongs to a family of putative helicases known as the DEAD box proteins. These proteins have been implicated in aspects of RNA function including translation initiation, splicing, and ribosome assembly in a variety of organisms ranging from Escherichia coli to humans. While members of this family are believed to function in the manipulation of RNA secondary structure, little is known about the regulation of these enzymes. By immunological methods and sequence comparison, we have found that p68 possesses a region of sequence similarity to the conserved protein kinase C phosphorylation site and calmodulin binding domain (also known as the IQ domain) of the neural-specific proteins neuromodulin (GAP-43) and neurogranin (RC3). We report that p68 is phosphorylated by protein kinase C in vitro and binds calmodulin in a Ca(2+)-dependent manner. Both phosphorylation and calmodulin binding inhibited p68 ATPase activity, suggesting that the RNA unwinding activity of p68 may be regulated by dual Ca2+ signal transduction pathways through its IQ domain.
人p68 RNA解旋酶是一种依赖于核RNA的ATP酶，属于一类被称为DEAD盒蛋白的假定解旋酶家族。这些蛋白在RNA功能的多个方面发挥作用，包括从大肠杆菌到人类等多种生物体中的翻译起始、剪接和核糖体组装。虽然该家族成员被认为在RNA二级结构的调控中发挥作用，但对这些酶的调节机制知之甚少。通过免疫学方法和序列比较，我们发现p68具有与神经特异性蛋白神经调节蛋白（GAP-43）和神经颗粒素（RC3）的保守蛋白激酶C磷酸化位点及钙调蛋白结合结构域（也称为IQ结构域）相似的序列区域。我们报道p68在体外被蛋白激酶C磷酸化，并以Ca(2+)依赖的方式结合钙调蛋白。磷酸化和钙调蛋白结合均抑制p68的ATP酶活性，这表明p68的RNA解旋活性可能通过其IQ结构域由双Ca2+信号转导途径调节。
