The α-carbon trace models of monomeric XOR.

<p>Panel A shows buffalo XOR while Panel B shows cattle XOR. The solid green color surface indicates the FAD molecule, the two 2Fe-2S (Fe/S) cofactor have been shown in space filling atomic representation in green (sulfur) and magenta (iron) color, while the Molybdenum cofactor (Moco) has been shown in ball and stick representation. The magenta color loop in buffalo XOR model, which is absent in electron density map of template cattle model (PDB ID: 3AMZ), connects the Fe/S domain (red color) with FAD domain (yellow color). The extended loop (residues 528–589) shown in green color connects the FAD domain with Moco domain (blue color). The residues shown with labels in buffalo XOR (Panel A) are only those which differed from corresponding residues in cattle XOR (Panel B) and also shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0087618#pone-0087618-t003" target="_blank">Table 3</a>. In case of template cattle XOR model, several loop structures were missing, which were built for buffalo XOR as described in the text.