1sk5: Difference between revisions

[[Image:1sk5.gif|left|200px]]

'''The ultra-high resolution structure of d(CTTTTAAAAG)2: modulation of bending by T-A steps and its role in DNA recognition'''

For the first time, ab initio direct methods have been used to solve the crystal structure of an RNA/DNA hybrid decamer. The RNA/DNA sequence corresponds to the leftmost two-thirds of the polypurine tract (PPT), the primer for second-strand DNA synthesis by HIV-1 reverse transcriptase (RT). Direct methods using Shake-and-Bake (SnB) yielded solutions for the RNA/DNA decamer molecule using 1.15 A data, which is just on the resolution edge of what might work with direct methods. Atomic positions for 96% of the entire molecule, containing 514 non-H atoms including three Ca(2+) ions, were easily interpreted from a Fourier map based on the 'Shake-and-Bake' minimal function and CROQUE phase-refinement program. Only six atoms, primarily in the sugar linkage, were missing in this Fourier map. At present, the R factor of the model is 0.143 (R(free) = 0.186) for the 562 non-H atom sites located. The conformation of the RNA/DNA helix is A-form, with a typical A-helix minor-groove width. This paper presents the methodology used in solving this structure.

Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1SK5 OCA].  

Direct-methods determination of an RNA/DNA hybrid decamer at 1.15 A resolution., Han GW, Acta Crystallogr D Biol Crystallogr. 2001 Feb;57(Pt 2):213-8. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/11173466 11173466]