Interactions at the Symmetric Mad2 Dimer Interface

<div><p>(A and B) Interactions between Mad2<sup>A</sup> and Mad2<sup>B</sup>. The side chains of contacting residues are shown as sticks. Nitrogen and oxygen atoms are colored blue and red, respectively. Mad2<sup>A</sup> carbons are colored yellow; Mad2<sup>B</sup> carbons are colored gray and labeled in italics. The tightly bound water molecules are drawn as red spheres.</p> <p>(C) Surface diagram of the Mad2<sup>L13A</sup> dimer. Same color scheme is used as in <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0060050#pbio-0060050-g003" target="_blank">Figure 3</a>A–<a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0060050#pbio-0060050-g003" target="_blank">3</a>C.</p> <p>(D) Hydrogen bonds with Q134 in Mad2<sup>A</sup>. Hydrogen bonds are indicated by red dashed lines.</p> <p>(E) Mad2<sup>R184E</sup> adopts the monomeric C-Mad2 conformation<b>.</b> Gel filtration chromatogram of the high-salt peak (275 mM salt, Q2) of Mad2<sup>R184E</sup> obtained with anion exchange chromatography is shown. Mad2<sup>R184E</sup> has an apparent molecular mass of about 30 kDa, which is consistent with it being a monomer. The elution profile for Mad2<sup>R184E</sup> is shown in red, and the elution profile for molecular weight standards is shown in gray. The positions for 44 kDa and 17 kDa markers are indicated.</p> <p>(F) The high-field methyl region of the 1D <sup>1</sup>H spectrum of Mad2<sup>R184E</sup>. The V197γ2 peak (−0.34 ppm) specific to C-Mad2 is labeled. The line width of the methyl peaks is consistent with C-Mad2<sup>R184E</sup> being monomeric.</p></div>