1hlx
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(New page: 200px<br /><applet load="1hlx" size="450" color="white" frame="true" align="right" spinBox="true" caption="1hlx" /> '''P1 HELIX NUCLEIC ACIDS (DNA/RNA) RIBONUCLEIC...)
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Revision as of 00:38, 25 November 2007
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P1 HELIX NUCLEIC ACIDS (DNA/RNA) RIBONUCLEIC ACID
Overview
The upstream cleavage site of group I self-splicing introns is identified, by an absolutely conserved U.G base-pair within a double helix. Mutant, introns with a wobble C.A substitute are catalytically active, but all, other combinations of nucleotides at these positions abolish splicing, suggesting that an unusual RNA structure generated by the wobble pair is, recognized by the catalytic intron core. The solution structure of a, 20-mer oligonucleotide containing a UUCG tetraloop hairpin and a U.G, wobble pair within a double helix was determined by NMR spectroscopy, without any assumptions on RNA conformation. Isotopically, (15N/13C)-labelled RNA was used to collect an unusually large number of, experimental constraints (703 in total, corresponding to approximately 35, constraints per nucleotide) leading to the determination of a structure, with very high precision (overall root-mean-square-deviation (rmsd), between 20 converged structures 1.22 A, local rmsd 0.6 A for the tetraloop, and 0.85 A for the stem). Analysis of the double helical structure at the, conserved U.G wobble pair reveals local distortions from the regular, A-form pattern, that may constitute the characteristic feature of U.G, wobble pair recognized by the group I intron core and by amino acyl tRNA, synthetases. Re-examination of the previously determined tetraloop, structure reveals a novel U.G base-pair with a syn guanosine and hydrogen, bonding contacts involving both base protons and a sugar 2'-OH. This, explains the great stability of RNA UUCG loops when compared with DNA, loops of identical sequence, and is one of the first NMR observations of, RNA 2'-OH resonances.
About this Structure
1HLX is a Protein complex structure of sequences from [1]. Full crystallographic information is available from OCA.
Reference
Structure of the P1 helix from group I self-splicing introns., Allain FH, Varani G, J Mol Biol. 1995 Jul 14;250(3):333-53. PMID:7608979
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