1p20

[[Image:1p20.gif|left|200px]]<br /><applet load="1p20" size="450" color="white" frame="true" align="right" spinBox="true"

caption="1p20, resolution 1.34&Aring;" />

'''Surprising Roles of Electrostatic Interactions in DNA-Ligand Complexes'''<br />

==Overview==

The positions of cations in x-ray structures are modulated by sequence, conformation, and ligand interactions. The goal here is to use x-ray, diffraction to help resolve structural and thermodynamic roles of, specifically localized cations in DNA-anthracycline complexes. We describe, a 1.34 A resolution structure of a CGATCG(2)-adriamycin(2) complex, obtained from crystals grown in the presence of thallium (I) ions. Tl(+), can substitute for biological monovalent cations, but is readily detected, by distinctive x-ray scattering, obviating analysis of subtle differences, in coordination geometry and x-ray scattering of water, sodium, potassium, and ammonium. Six localized Tl(+) sites are observable adjacent to each, CGATCG(2)-adriamycin(2) complex. Each of these localized monovalent, cations are found within the G-tract major groove of the intercalated, DNA-drug complex. Adriamycin appears to be designed by nature to interact, favorably with the electrostatic landscape of DNA, and to conserve the, distribution of localized cationic charge. Localized inorganic cations in, the major groove are conserved upon binding of adriamycin. In the minor, groove, inorganic cations are substituted by a cationic functional group, of adriamycin. This partitioning of cationic charge by adriamycin into the, major groove of CG base pairs and the minor groove of AT base pairs may be, a general feature of sequence-specific DNA-small molecule interactions and, a potentially useful important factor in ligand design.

 

==About this Structure==

1P20 is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/ ] with DM2 and TL as [http://en.wikipedia.org/wiki/ligands ligands]. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1P20 OCA].

 

==Reference==

Surprising roles of electrostatic interactions in DNA-ligand complexes., Howerton SB, Nagpal A, Williams LD, Biopolymers. 2003 May;69(1):87-99. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=12717724 12717724]

[[Category: Protein complex]]

[[Category: Howerton, S.B.]]

[[Category: Nagpal, A.]]

[[Category: Williams, L.D.]]

[[Category: adriamycin]]

[[Category: electrostatics]]

[[Category: intercalation]]

[[Category: thallium]]