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== Publication Abstract from PubMed ==

The crystal structure of the RNA dodecamer 5'-GGCC(GAAA)GGCC-3' has been determined from x-ray diffraction data to 2.3-A resolution. In the crystal, these oligomers form double helices around twofold symmetry axes. Four consecutive non-Watson-Crick base pairs make up an internal loop in the middle of the duplex, including sheared G.A pairs and novel asymmetric A.A pairs. This internal loop sequence produces a significant curvature and narrowing of the double helix. The helix is curved by 34 degrees from end to end and the diameter is narrowed by 24% in the internal loop. A Mn2+ ion is bound directly to the N7 of the first guanine in the Watson-Crick region following the internal loop and the phosphate of the preceding residue. This Mn2+ location corresponds to a metal binding site observed in the hammerhead catalytic RNA.

A curved RNA helix incorporating an internal loop with G.A and A.A non-Watson-Crick base pairing.,Baeyens KJ, De Bondt HL, Pardi A, Holbrook SR Proc Natl Acad Sci U S A. 1996 Nov 12;93(23):12851-5. PMID:8917508<ref>PMID:8917508</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>

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== References ==

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