Figure 6.

Genetic variants have demonstrated the importance of a conserved arginine (R) residue for H₂ activation by E. coli Hyd-1. (A) X-ray crystal structure of wild type Hyd-1, with a guanidinium group of arginine (R) 509 positioned above the active site. (B) Activity assays for wild type and variant Hyd-1, showing the effect of different mutations in the active site canopy. The aspartic acid (D) 118 and 574 variants are discussed later. (C) X-ray crystal structure of the R509K variant. Adapted with permission from ref (54). Copyright 2015 Nature Publishing Group.