The dawn of dominance by the mature domain in tRNA splicing
- *Istituto di Biologia Cellulare, Consiglio Nazionale delle Ricerche, Campus A, Buzzati-Traverso, Via Ramarini 32, Monterotondo Scalo, 00016 Rome, Italy; and
- †Istituto di Genetica Molecolare, Consiglio Nazionale delle Ricerche, Via Abbiategrasso 207, I-27100 Pavia, Italy
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Communicated by Robert Haselkorn, University of Chicago, Chicago, IL, June 13, 2007 (received for review May 23, 2007)
Abstract
The relationship between enzyme architecture and substrate specificity among archaeal pre-tRNA splicing endonucleases has been investigated more deeply, by using biochemical assays and model building. The enzyme from Archeoglobus fulgidus (AF) is particularly interesting: it cleaves the bulge–helix–bulge target without requiring the mature tRNA domain, but, when the target is a bulge–helix–loop, the mature domain is required. A model of AF based on its electrostatic potential shows three polar patches interacting with the pre-tRNA substrate. A simple deletion mutant of the AF endonuclease lacking two of the three polar patches no longer cleaves the bulge–helix–loop substrate with or without the mature domain. This single deletion shows a possible path for the evolution of eukaryal splicing endonucleases from the archaeal enzyme.
Footnotes
- ‡To whom correspondence should be addressed. E-mail: gtocchini{at}ibc.cnr.it
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Author contributions: G.D.T.-V., P.F., and G.P.T.-V. designed research, performed research, contributed new reagents/analytic tools, analyzed data, and wrote the paper.
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The authors declare no conflict of interest.
- Abbreviations:
- NAF,
- N-terminal repeat;
- CAF,
- C-terminal repeat;
- BHB,
- bulge–helix–bulge;
- BHL,
- bulge–helix–loop;
- SS,
- Sulfolobus solfataricus;
- AF,
- Archeoglobus fulgidus;
- MJ,
- Methanocaldococcus jannaschii.
- © 2007 by The National Academy of Sciences of the USA
