期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 100, 期 26, 页码 15469-15474出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.2536698100
关键词
catalytic magnesium; Gre proteins
资金
- NIGMS NIH HHS [GM49242, R01 GM030717, GM30717] Funding Source: Medline
During transcription elongation, RNA polymerase (RNAP) occasionally loses its grip on the growing RNA end and backtracks on the DNA template. Prokaryotic Gre factors rescue the backtracked ternary elongating complex through stimulation of an intrinsic endonuclease activity, which removes the disengaged 3' RNA segment. By using RNA-protein crosslinking in defined ternary elongating complexes, site-directed mutagenesis, discriminative biochemical assays, and docking of the two protein structures, we show that Gre acts by providing two carboxylate residues for coordination of catalytic Mg2+ ion in the RNAP active center. A similar mechanism is suggested for the functionally analogous eukaryotic SII factor. The results expand the general two-metal model of RNAP catalytic mechanism whereby one of the Mg2+ ions is permanently retained, whereas the other is recruited ad hoc by an auxiliary factor.
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