Iron-sulfur proteins with [2Fe-2S] clusters are involved in oxidation-reduction reactions of aerobic and anaerobic metabolism. The [2Fe-2S] clusters are incorporated into proteins homologous to either plant-type or mammalian-type ferredoxins.
Aquifex aeolicus is a bacteria which can grow on hydrogen, oxygen, carbon dioxide, and mineral salts at temperatures near 95C; therefore, it is highly thermophilic. The fdx4 gene from Aquifex aeolicus was overexpressed in Escherichia coli, allowing for isolation and characterization of AaFd4 which is involved in electron transport. This was the first hyperthermophilic [2Fe-2S](Scys)4 protein characterized and can withstand heating to 100C for 3 hours.
The crystal structure of AaFd4 will be analyzed in this presentation. AaFd4 includes a thioredoxin-like fold which is novel to iron-sulfur proteins. Although thioredoxin has been studied most in E. coli, the thioredoxin-like fold in AaFd4 will be compared with that of thioredoxin-2 from Anabaena in this presentation.