Science：新发现为生命的第一个遗传分子研究提供线索
新研究为生命的第一个遗传分子可能是什么样的提供了线索。生物都靠由DNA组成的基因和蛋白质酶来实现细胞功能的。大约40年前，研究人员提出“RNA世界”的假说，他们认为在生命的最初，RNA可能出现在基因和酶之前，因为RNA既能催化反应也包含遗传信息，所以第一个遗传分子是能自我拷贝的RNA。虽然自然界中没有能将RNA分子连接起来的RNA酶，而这是RNA世界的一个关键的必要条件，但是研究人员合成了这样一个酶。现在Michael P. Robertson和William G. Scott确定出这个被称为“连接核酶”的结构。其活性点的结构提示，该核酶用已知的自然界核酶所用的生物化学战略。一篇相关的研究评述进一步讨论了这些发现。
部分英文原文：
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Science 16 March 2007: |
The Structural Basis of Ribozyme-Catalyzed RNA Assembly
Life originated, according to the RNA World hypothesis, from self-replicating ribozymes that catalyzed ligation of RNA fragments. We have solved the 2.6 angstrom crystal structure of a ligase ribozyme that catalyzes regiospecific formation of a 5' to 3' phosphodiester bond between the 5'-triphosphate and the 3'-hydroxyl termini of two RNA fragments. Invariant residues form tertiary contacts that stabilize a flexible stem of the ribozyme at the ligation site, where an essential magnesium ion coordinates three phosphates. The structure of the active site permits us to suggest how transition-state stabilization and a general base may catalyze the ligation reaction required for prebiotic RNA assembly.
The Center for the Molecular Biology of RNA and Department of Chemistry and Biochemistry, Robert L. Sinsheimer Laboratories, University of California, Santa Cruz, Santa Cruz, CA 95064, USA.
* To whom correspondence should be addressed. E-mail: wgscott@chemistry.ucsc.edu
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