Duan X, Gimble F S, Quiocho F A
Structural and Computational Biology and Molecular Biophysics Program, Baylor College of Medicine, Houston, Texas 77030, USA.
Cell. 1997 May 16;89(4):555-64. doi: 10.1016/s0092-8674(00)80237-8.
PI-Scel is a bifunctional yeast protein that propagates its mobile gene by catalyzing protein splicing and site-specific DNA double-strand cleavage. Here, we report the 2.4 A crystal structure of the PI-Scel protein. The structure is composed of two separate domains (I and II) with novel folds and different functions. Domain I, which is elongated and formed largely from seven beta sheets, harbors the N and C termini residues and two His residues that are implicated in protein splicing. Domain II, which is compact and is primarily composed of two similar alpha/beta motifs related by local two-fold symmetry, contains the putative nuclease active site with a cluster of two acidic residues and one basic residue commonly found in restriction endonucleases. This report presents prototypic structures of domains with single endonuclease and protein splicing active sites.
PI-Scel是一种双功能酵母蛋白，它通过催化蛋白质剪接和位点特异性DNA双链切割来传播其可移动基因。在此，我们报道了PI-Scel蛋白2.4埃的晶体结构。该结构由两个具有新颖折叠和不同功能的独立结构域（结构域I和结构域II）组成。结构域I呈细长形，主要由七个β折叠组成，包含N端和C端残基以及两个与蛋白质剪接有关的组氨酸残基。结构域II较为紧凑，主要由两个通过局部二重对称相关的相似α/β基序组成，包含推定的核酸酶活性位点，该位点有一组在限制性内切核酸酶中常见的两个酸性残基和一个碱性残基。本报告展示了具有单核酸内切酶和蛋白质剪接活性位点的结构域的原型结构。
