A model of the effect of methylation on Arg38 in the DBD3 AT-hook.

<p>Only the guanidinium group of Arg38 (in blue) is visible in this orientation. DNA is shown in grey. In this model the hydrogen bonds between the arginine guanidinium group and the minor groove of DNA are maintained, whereas the methyl group (in red) has an external position. In the side facing DNA there is no room for the methyl group, without disturbing the guanidinium-DNA hydrogen bonds.</p

In this figure the DNA duplex is shown as space filling atoms with their van der Waals radii.

<p>The strong association of the inner PRGRP sequence with the duplex is clearly visible. The terminal basic amino acids (34, 40 and 41) interact with phosphates in the same duplex, with the exception of Arg33 which does not show any apparent interactions.</p

Crystal data and refinement statistics.

<p>Values in parentheses are for the last shell.</p>a<p>.</p>b<p><i>R</i> factor of reflections used for cross validation in the refinement.</p

Electron density map (2F_o-F_c at 1σ level) of a segment of the AT-hook in the minor groove of DNA.

<p>Hydrogen bonds between main chain peptide NH atoms (Gly37 and Arg38) and thymine oxygen atoms are indicated as red dashed lines.</p

Comparison of the structures of the central PRGRP sequence of the AT-hook obtained by either X-ray diffraction (in grey, this work) or NMR [<b>10</b>].

<p>The overall conformation is similar, but the X-ray structure has significant changes in the position of the main chain NH groups, which allow the formation of hydrogen bonds with minor groove thymine oxygen atoms of DNA. This figure has been prepared with Cerius2.</p