High resolution crystal structures of oxidized and semi-reduced S35C flavodoxin mutant from Desulfovibrio vulgaris

Engineered flavodoxins in which a surface residue has been replaced by an exposed cysteine are useful modules to link multi-domain redox proteins to electrode surfaces [1] [2] [3]. The crystal structure of the S35C mutant of Desulfovibrio vulgaris flavodoxin in the oxidized state [4] has been compared with the structure of the semi-reduced form (semiquinone) obtained with sodium dithionite as reducing agent. The structure of S35C oxidized form (P43212, a=50.65Å, b=50.65Å, c=138.08Å) at 1.2 Å resolution has been refined to R=0.16 and Rfree=0.18. The structure of the reduced S35C mutant (P43212, a=50.86Å, b=50.86Å, c=138Å) at 1.4 Å resolution has been refined to R=0.20 and Rfree=0.24. Data sets were collected with synchrotron radiation at 100 K on ELETTRA beamline. Comparison of the two structures with particular emphasis on the features that are related to the differences in the oxidation state of the cofactor FMN have been made.