1f9l
From Proteopedia
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SOLUTION STRUCTURE OF A 22-NUCLEOTIDE HAIRPIN SIMILAR TO THE P5ABC REGION OF A GROUP I RIBOZYME WITH COBALT(III)HEXAMMINE COMPLEXED TO THE GAAA TETRALOOP
Overview
The solution structure of a 22 nt RNA hairpin and its complex with, Co(NH(3))(6)(3+) bound to the GAAA tetraloop has been determined by NMR, spectroscopy. Co(NH(3))(6)(3+) has a similar geometry to Mg(H(2)O)(6)(2+), and can be used as a probe for binding sites of completely solvated, magnesium ions. The hairpin contains tandem G.A mismatches, similar to the, P5abc region of a group I intron, and is closed by a GAAA tetraloop. The, tandem G.A mismatches are imino hydrogen bonded in contrast with the, sheared G.A mismatches found in a different context in the crystal, structure of the P4-P6 domain. Chemical shift changes of the imino protons, upon titration of the RNA hairpin with Mg(2+) and with Co(NH(3))(6)(3+), were used to identify ion-binding sites. Paramagnetic resonance broadening, upon titration with Mn(2+) was also used. The titration curves gave, dissociation binding constants for the magnesium ions in the millimolar, range, similar to the binding in the major groove of RNA at tandem G.U, base-pairs. Although the largest chemical shift change occurred at an, imino proton of one of the G.A base-pairs, no nuclear Overhauser, enhancement cross-peaks between the cobalt ligand and neighboring RNA, protons were seen, presumably due to the high mobility of the, Co(NH(3))(6)(3+) at this site. Nuclear Overhauser enhancement cross-peaks, between Co(NH(3))(6)(3+) and the GAAA tetraloop were observed, which, allowed the determination of the structure of the tetraloop binding site., The Co(NH(3))(6)(3+) is bound in the major groove of the GAAA tetraloop, with hydrogen bonds to guanine base N7 and to phosphate oxygen atoms of, the tetraloop.
About this Structure
1F9L is a Protein complex structure of sequences from [1]. Full crystallographic information is available from OCA.
Reference
Solution structure of Cobalt(III)hexammine complexed to the GAAA tetraloop, and metal-ion binding to G.A mismatches., Rudisser S, Tinoco I Jr, J Mol Biol. 2000 Feb 4;295(5):1211-23. PMID:10653698
Page seeded by OCA on Sat Nov 24 23:31:54 2007
