Despite their high sequence homology, rubredoxins fromDesulfovibrio gigasandD. desulfuricansare stabilized to very different extents by com-patible solutes such as diglycerol phosphate, the major osmolyte in the hyperthermophilic archaeonArchaeoglobus fulgidus[Lamosa P, Burke A, Peist R, Huber R, Liu M Y, Silva G, Rodrigues-Pousada C, LeGall J, Maycock C and Santos H (2000)Appl Environ Microbiol66, 1974–1979]. The principal structural difference between these two proteins is the absence of the hairpin loop in the rubredoxin fromD. desulfuricans
