Lim F, Spingola M, Peabody D S
Department of Cell Biology, University of New Mexico School of Medicine, and Cancer Research and Treatment Center, Albuquerque, New Mexico 87131, USA.
J Biol Chem. 1996 Dec 13;271(50):31839-45. doi: 10.1074/jbc.271.50.31839.
The coat proteins of the RNA bacteriophages Qbeta and MS2 are specific RNA binding proteins. Although they possess common tertiary structures, they bind different RNA stem loops and thus provide useful models of specific protein-RNA recognition. Although the RNA-binding site of MS2 coat protein has been extensively characterized previously, little is known about Qbeta. Here we describe the isolation of mutants that define the RNA-binding site of Qbeta coat protein, showing that, as with MS2, it resides on the surface of a large beta-sheet. Mutations are also described that convert Qbeta coat protein to the RNA binding specificity of MS2. The results of these and other studies indicate that, although they bind different RNAs, the binding sites of the two coat proteins are sufficiently similar that each is easily converted by mutation to the RNA binding specificity of the other.
RNA噬菌体Qβ和MS2的外壳蛋白是特异性RNA结合蛋白。尽管它们具有共同的三级结构，但它们结合不同的RNA茎环，因此提供了特异性蛋白质-RNA识别的有用模型。虽然MS2外壳蛋白的RNA结合位点此前已得到广泛表征，但对Qβ却知之甚少。在此，我们描述了定义Qβ外壳蛋白RNA结合位点的突变体的分离，结果表明，与MS2一样，它位于一个大β折叠的表面。还描述了将Qβ外壳蛋白转变为具有MS2 RNA结合特异性的突变。这些研究和其他研究的结果表明，尽管这两种外壳蛋白结合不同的RNA，但它们的结合位点足够相似，以至于通过突变，每种蛋白都很容易转变为另一种蛋白的RNA结合特异性。
