Figure 6.

Mrx2 cluster alignment and active-site interaction. A, alignment of the amino acid sequences of the Mrx2 cluster (salmon and deep purple) proposed by phylogenetic analysis. The figure was prepared with Boxshade, a web-based program hosted by Expasy (www.expasy.org). B, the hydrogen bonding environment of the Cys¹⁹ sulfur is depicted by black dashed lines, and the respective distances between heavy atoms are given in Å. C, by rotating the side chain of Asp¹⁶ (the stereochemistry of this residue was also optimized using the “regularize zone” function in COOT) the carboxylate oxygen forms a close interaction with the sulfur of Cys²². The Rv2466c α-helical bundle is shown in yellow, and the thioredoxin fold is shown in orange.