Schematic illustration of the topology of PQ-loop proteins.

<p>Helices are shown in red, the termini and connecting loops in black. Arrows indicate the approximate boundaries of the InterPro annotated regions in human proteins: CTNSR (yellow), PQLR (green), MtN3_saliva (blue). The most conserved amino acids are indicated in violet boxes. For the exact sequence positions of these features see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0030876#pone-0030876-g003" target="_blank">Fig. 3</a> in which the same colour scheme is used.