Unique and ancient metabolic strategies: the purification of novel methanogen sulfur trafficking proteins

Sulfur trafficking pathways in methanogens are distinct from bacteria because sulfide rather than sulfate, is the primary sulfur source. Many methanogens also lack the genes coding for O-acetylhomoserine sulfhydrylase, O-acetylserine sulfhydrylase, cysteine desulfurase, and cysteinyl-tRNA synthase (CysRS), all essential sulfur trafficking enzymes in bacteria.