Iron-sulfur cluster biosynthesis: characterization of a molten globule domain in human NFU.
Human NFU (also known as HIRIP5) has been implicated in cellular iron-sulfur cluster biosynthesis. Bacterial and yeast forms are smaller than the human protein and are homologous to the C-terminal domain of human NFU. This C-terminal domain contains a pair of redox active cysteines and demonstrates thioredoxin-like activity by both binding to and mediating persulfide bond cleavage of sulfur-loaded IscS, the sulfide donor for [2Fe-2S] cluster assembly on ISU-type scaffold proteins. Herein, human NFU is shown to possess a novel combination of a molten globule-type C-terminal domain and an N-terminal domain with a fully folded regular tertiary structure. The molten globule characteristics of the C-terminal domain have been evaluated by 1-anilino-8-naphthalenesulfonic acid binding, the kinetics of trypsin digestion, and heteronuclear single-quantum coherence nuclear magnetic resonance studies. Human NFU is a functionally competent reducing agent for cysteinyl persulfide bond cleavage, releasing inorganic sulfide for incorporation into the ISU-bound [2Fe-2S] cluster, a reactivity that might be facilitated by the flexibility of the C-terminal domain.
Liu
Yushi
Y
Evans Laboratory of Chemistry, The Ohio State University, Columbus, Ohio 43210, USA.
Cowan
J A
JA
D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000096:biosynthesis / Q000737:chemistry* / Q000378:metabolism; D003545:Cysteine / Q000031:analogs & derivatives / Q000737:chemistry; D004220:Disulfides / Q000737:chemistry; D006801:Humans; D007506:Iron-Sulfur Proteins / Q000096:biosynthesis / Q000737:chemistry* / Q000378:metabolism; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010446:Peptide Fragments / Q000096:biosynthesis / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D019163:Reducing Agents / Q000737:chemistry; D013329:Structure-Activity Relationship; D013816:Thermodynamics
D002352:Carrier Proteins; D004220:Disulfides; D007506:Iron-Sulfur Proteins; C426067:NFU1 protein, human; D010446:Peptide Fragments; D019163:Reducing Agents; C116840:cysteine persulfide; D003545:Cysteine