Figure 5

Interactions of the Lys 46 sidechain in the NMR-derived metal binding site-swapped rubredoxin structures. As observed in the X-ray crystal structures of both Cp and Pf rubredoxins, the ε-amino group of Lys 46 hydrogen bonds to the backbone carbonyl oxygens of residues 30 and 33. An additional interaction with the carboxyl sidechain of Asp 35 is observed in the metal binding site-swapped Cp rubredoxin (thick-line structure). In contrast, the Asp 35 carboxyl of the metal binding site-swapped Pf rubredoxin (thin-line structure) is rotated away toward the aqueous phase, more closely approaching the solvent-exposed Asp 35 H^N.