The dimeric structure of Sulfolobus solfataricus thioredoxin A2 and the basis of its thermostability.

The crystallographic characterization of SsTrxA2 reveals that the redox active center is buried by the dimeric interface of the protein. This suggests that pro- ductive interactions of the protein with its biological partners require a preliminary dissociation of the dimer. Although further studies are needed to fully address the biological implications of this finding, it can be specu- lated that this peculiar feature of SsTrxA2 may be impor- tant for the regulation of the protein activity. A struc- tural comparison of SsTrxA2 with the closely-related StTrxA2 suggests that minimal aminoacids substitutions may have a strong impact on the oligomerization state of the protein.