327d

[[Image:327d.gif|left|200px]]<br /><applet load="327d" size="350" color="white" frame="true" align="right" spinBox="true"

caption="327d, resolution 1.940&Aring;" />

'''CRYSTAL STRUCTURES OF D(GM5CGM5CGCGCGC)'''<br />

==Overview==

It is well known that methylation of alternating Py x Pu sequences, potentiates the formation of Z-DNA. However, we have now observed that, methylation of the alternating Z-DNA oligomer d(GCGCGCGCGC), which starts, with a 5'-purine, unexpectedly stabilizes the A-DNA conformation. The, double methyl derivative d(Gm5CGm5CGCGCGC), which crystallizes as duplex, A-DNA in the hexagonal space group P6(1)22, a = b = 39.33 A and c = 77.93, A with one strand per asymmetric unit and six duplexes in the unit cell, refined to an R factor of 19.1 for 204 DNA atoms and 43 solvent molecules., This is the first report of a DNA sequence crystallized in both right and, left-handed conformations, allowing structural comparisons not previously, possible and, more importantly, this is the first time that methylation, has been shown to potentiate the formation of A-DNA from a sequence known, to crystallize as Z-DNA. From this study, ten base-pairs appear to be the, critical length in determining the handedness of d(GC)n-type sequences in, the crystalline state. Because methylation of nuclear DNA is linked to a, number of cellular processes, including transcriptional inactivation, this, study has important implications for the role of A-DNA in methylated, regions of genomic DNA and, thus, in the regulation of gene expression. In, this context, the structure of d(Gm5Cm5CGCGCGC) will be compared with that, of the alternating A-DNA decamer d(GCACGCGTGC) and the alternating Z-DNA, decamer d(GCGCGCGCGC) and discussed in terms of the forces that govern the, handedness of duplex DNA oligomers.

 

==About this Structure==

327D 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://oca.weizmann.ac.il/oca-bin/ocashort?id=327D OCA].

 

==Reference==

Methylation of the Z-DNA decamer d(GC)5 potentiates the formation of A-DNA: crystal structure of d(Gm5CGm5CGCGCGC)., Tippin DB, Ramakrishnan B, Sundaralingam M, J Mol Biol. 1997 Jul 11;270(2):247-58. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=9236126 9236126]

[[Category: Protein complex]]

[[Category: Ramakrishnan, B.]]

[[Category: Sundaralingam, M.]]

[[Category: Tippin, D.B.]]

[[Category: a-dna]]

[[Category: double helix]]

[[Category: modified]]

 

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