1jb8

[[Image:1jb8.gif|left|200px]]<br />

<applet load="1jb8" size="450" color="white" frame="true" align="right" spinBox="true"

caption="1jb8, resolution 2.38&Aring;" />

'''The Crystal Structure of an RNA/DNA Hybrid Reveals Novel Intermolecular Intercalation'''<br />

==Overview==

An intermolecular intercalation of base pairs was found at the CA step in, the I222 crystal structure of the RNA.DNA hybrid, r(CAAAGAAAAG).d(CTTTTCTTTG), which contains two-thirds of the polypurine, tract sequence of HIV-1 with a substitution of cytosine for the initial, adenine. This sequence crystallized in both P212121 and I222 space groups, with an rms difference of only 0.63 A between residues 3 to 18 of the two, forms. P212121 and I222 helices are both A-like, but intercalation occurs, only in the I222 crystal form. The present structure shows bases stacked, in parallel rather than perpendicular as in intercalated DNA (I-DNA). The, base intercalation is also different from zipper-like meshing of bases, seen in the center of the crystal structure of d(GCGAAAGCT), which does, not have Watson-Crick base pairing. The base-step intercalation seen here, is reminiscent of domain swapping in proteins; therefore, we call this, phenomenon "base-pair swapping." It involves a highly mobile CA step and, seems to be sequence-specific and electrostatically stable without, disrupting Watson-Crick interactions. It also exhibits a large rise, concurrent with unwinding of the helix (low twist). We present a base-pair, swapping dimer in nucleic acids.

 

==About this Structure==

1JB8 is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/ ]. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1JB8 OCA].

 

==Reference==

Crystal structure of an RNA.DNA hybrid reveals intermolecular intercalation: dimer formation by base-pair swapping., Han GW, Kopka ML, Langs D, Sawaya MR, Dickerson RE, Proc Natl Acad Sci U S A. 2003 Aug 5;100(16):9214-9. Epub 2003 Jul 18. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=12872000 12872000]

[[Category: Protein complex]]

[[Category: Dickerson, R.E.]]

[[Category: Han, G.W.]]

[[Category: Kopka, M.L.]]

[[Category: Langs, D.]]

[[Category: dna/dna intercalation]]

[[Category: rna/dna hybrid]]

[[Category: rna/dna polypurine tract]]

 

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