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| {{STRUCTURE_1i3x| PDB=1i3x | SCENE= }} | | {{STRUCTURE_1i3x| PDB=1i3x | SCENE= }} |
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| '''SOLUTION STRUCTURE OF THE A LOOP OF 23S RIBOSOMAL RNA'''
| | ===SOLUTION STRUCTURE OF THE A LOOP OF 23S RIBOSOMAL RNA=== |
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| ==Overview==
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| The A loop is an essential RNA component of the ribosome peptidyltransferase center that directly interacts with aminoacyl (A)-site tRNA. The A loop is highly conserved and contains a ubiquitous 2'-O-methyl ribose modification at position U2552. Here, we present the solution structure of a modified and unmodified A-loop RNA to define both the A-loop fold and the structural impact of the U2552 modification. Solution data reveal that the A-loop RNA has a compact structure that includes a noncanonical base pair between C2556 and U2552. NMR evidence is presented that the N3 position of C2556 has a shifted pKa and that protonation at C2556-N3 changes the C-U pair geometry. Our data indicate that U2552 methylation modifies the A-loop fold, in particular the dynamics and position of residues C2556 and U2555. We compare our structural data with the structure of the A loop observed in a recent 50S crystal structure [Ban, N., Nissen, P., Hansen, J., Moore, P. B. & Steitz, T. A. (2000) Science 289, 905--920; Nissen, P., Hansen, J., Ban, N., Moore, P. B. & Steitz, T. A. (2000) Science 289, 920--930]. The solution and crystal structures of the A loop are dramatically different, suggesting that a structural rearrangement of the A loop must occur on docking into the peptidyltransferase center. Possible roles of this docking event, the shifted pKa of C2556 and the U2552 2'-O-methylation in the mechanism of translation, are discussed. | | The line below this paragraph, {{ABSTRACT_PUBMED_11259644}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 11259644 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_11259644}} |
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| ==About this Structure== | | ==About this Structure== |
| Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1I3X OCA]. | | Full experimental information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1I3X OCA]. |
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| ==Reference== | | ==Reference== |
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| [[Category: A loop]] | | [[Category: A loop]] |
| [[Category: A site]] | | [[Category: A site]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 19:32:32 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 1 10:22:44 2008'' |
