1fix

<StructureSection load='1fix' size='340' side='right' caption='[[1fix]], [[Resolution|resolution]] 2.30&Aring;' scene=''>

<table><tr><td colspan='2'>[[1fix]] is a 2 chain structure. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1FIX OCA]. For a <b>guided tour on the structure components</b> use [http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1FIX FirstGlance]. <br>

</td></tr><tr><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1fix FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1fix OCA], [http://www.rcsb.org/pdb/explore.do?structureId=1fix RCSB], [http://www.ebi.ac.uk/pdbsum/1fix PDBsum]</span></td></tr>

The structure of a complementary hybrid duplex of RNA and DNA has been determined by X-ray crystallography. A ten residue DNA oligonucleotide of sequence 5'-G-G-C-G-C-C-C-G-A-A-3' was annealed to complementary RNA (5'-u-u-c-g-g-g-c-g-c-c-3') and crystallized, producing tetragonal crystals that diffract to 2.3 A resolution. The hybrid adopts a geometry that is neither strictly A nor B-form, rather the helix possesses qualities of both, reminiscent of spectroscopic descriptions of a hybrid conformation, or H-form. All of the ribonucleotides maintain the C3'-endo conformation seen in A-form, while both C3'-endo and C2'-endo conformations are found in the deoxyribonucleotides. The minor groove width (8.5 to 10.5 A) is intermediate between standard values for A (11 A) and B-form (7.4 A) DNA. The global parameters rise and base-pairs tilt (or inclination) are like that of A-DNA, however the slide and x displacement (Dx) are more like that of A-RNA, thus giving the hybrid a unique conformation. In addition, the 10-mer crystallizes in a manner that allows the formation of dimers that stack end-to-end, thereby providing a glimpse of how an extended (20 base-pair) helix of RNA-DNA hybrid might appear. This duplex sequence was selected for study because it is specifically recognized by the ribonuclease H function of HIV reverse transcriptase. A structure of a substrate of this enzyme is of potential value in understanding requirements for the selectivity of this important drug target. The minor groove of the hybrid duplex, lined with the 2-OH of the ribose rings, is the single distinguishing characteristic of the RNA/DNA hybrid, undoubtedly an important structural feature conferring selectivity.

 

The structure of an RNA/DNA hybrid: a substrate of the ribonuclease activity of HIV-1 reverse transcriptase.,Horton NC, Finzel BC J Mol Biol. 1996 Dec 6;264(3):521-33. PMID:8969302<ref>PMID:8969302</ref>

 

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<references/>

[[Category: Finzel, B C.]]

[[Category: Horton, N C.]]

[[Category: Dna-rna hybrid]]

[[Category: Right handed dna/rna hybrid]]