Zwieb C, Müller F, Larsen N
Department of Molecular Biology, University of Texas Health Science Center, Tyler 75710, USA.
Fold Des. 1996;1(4):315-24. doi: 10.1016/S1359-0278(96)00044-2.
The signal recognition particle (SRP) is a ribonucleoprotein complex that associates with ribosomes to promote co-translational translocation of proteins across biological membranes. We have used comparative analysis of a large number of bacterial, archaeal, and eukaryotic SRP RNA sequences to derive shared tertiary SRP RNA structure elements.
A representative three-dimensional model of the human SRP RNA is shown that includes single-stranded intrahelical and interhelical RNA loops and incorporates data from enzymatic and chemical modification, electron microscopy, and site-directed mutagenesis. Properties of the SRP RNA model are an overall extended dumbbell-shaped structure (260 A x 70 A) with a pseudoknot in the small SRP domain (a pairing of 12-UGGC-15 with 33-GCUA-36), and a tertiary interaction in the large SRP domain (198-GA-199 with 232-GU-233).
The RNA 'knuckle' formed in helix 8 of SRP RNA appears to constitute the binding site for protein SRP54 or its bacterial equivalent, protein P48. A dynamic property of this feature may explain the hierarchial assembly of proteins SRP19 and SRP54 in the large SRP domain. Furthermore, the human SRP RNA model serves as a framework to understand details of the structure and function of SRP in all organisms and is presented to stimulate further experimentation in this area.
信号识别颗粒（SRP）是一种核糖核蛋白复合体，它与核糖体结合以促进蛋白质跨生物膜的共翻译转运。我们通过对大量细菌、古细菌和真核生物的SRP RNA序列进行比较分析，得出了共享的三级SRP RNA结构元件。
展示了人类SRP RNA的一个代表性三维模型，该模型包括单链螺旋内和螺旋间RNA环，并纳入了酶促和化学修饰、电子显微镜及定点诱变的数据。SRP RNA模型的特性是整体呈伸展的哑铃形结构（260 Å×70 Å），在小SRP结构域有一个假结（12 - UGGC - 15与33 - GCUA - 36配对），在大SRP结构域有一个三级相互作用（198 - GA - 199与232 - GU - 233）。
SRP RNA螺旋8中形成的RNA“关节”似乎构成了蛋白质SRP54或其细菌等效物蛋白质P48的结合位点。这一特征的动态特性可能解释了大SRP结构域中蛋白质SRP19和SRP54的层级组装。此外，人类SRP RNA模型为理解所有生物体中SRP的结构和功能细节提供了一个框架，并旨在激发该领域的进一步实验。
