title: Cysteine is not the sulfur source for iron-sulfur cluster and methionine biosynthesis in the methanogenic archaeon Methanococcus maripaludis.
abstract: Three multiprotein systems are known for iron-sulfur (Fe-S) cluster biogenesis in prokaryotes and eukaryotes as follows: the NIF (nitrogen fixation), the ISC (iron-sulfur cluster), and the SUF (mobilization of sulfur) systems. In all three, cysteine is the physiological sulfur source, and the sulfur is transferred from cysteine desulfurase through a persulfidic intermediate to a scaffold protein. However, the biochemical nature of the sulfur source for Fe-S cluster assembly in archaea is unknown, and many archaea lack homologs of cysteine desulfurases. Methanococcus maripaludis is a methanogenic archaeon that contains a high amount of protein-bound Fe-S clusters (45 nmol/mg protein). Cysteine in this archaeon is synthesized primarily via the tRNA-dependent SepRS/SepCysS pathway. When a ΔsepS mutant (a cysteine auxotroph) was grown with (34)S-labeled sulfide and unlabeled cysteine, <8% of the cysteine, >92% of the methionine, and >87% of the sulfur in the Fe-S clusters in proteins were labeled, suggesting that the sulfur in methionine and Fe-S clusters was derived predominantly from exogenous sulfide instead of cysteine. Therefore, this investigation challenges the concept that cysteine is always the sulfur source for Fe-S cluster biosynthesis in vivo and suggests that Fe-S clusters are derived from sulfide in those organisms, which live in sulfide-rich habitats.
authors: Department of Microbiology, University of Georgia, Athens, Georgia 30602-2605, USA.
authors: Yuchen
authors: Y
authors: Liu
authors: Magdalena
authors: M
authors: Sieprawska-Lupa
authors: William B
authors: WB
authors: Whitman
authors: Robert H
authors: RH
authors: White
mesh_terms: D019843:Archaeal Proteins / Q000096:biosynthesis*; D003545:Cysteine / Q000737:chemistry / Q000378:metabolism*; D007506:Iron-Sulfur Proteins / Q000096:biosynthesis*; D017017:Methanococcus / Q000737:chemistry / Q000378:metabolism*; D008715:Methionine / Q000096:biosynthesis*; D013455:Sulfur / Q000378:metabolism*
chemical_list: D019843:Archaeal Proteins; D007506:Iron-Sulfur Proteins; D013455:Sulfur; D008715:Methionine; D003545:Cysteine