title: Iron-sulfur cluster binding by mitochondrial monothiol glutaredoxin-1 of Trypanosoma brucei: molecular basis of iron-sulfur cluster coordination and relevance for parasite infectivity.
abstract: OBJECTIVE
  Monothiol glutaredoxins (1-C-Grxs) are small proteins linked to the cellular iron and redox metabolism. Trypanosoma brucei brucei, model organism for human African trypanosomiasis, expresses three 1-C-Grxs. 1-C-Grx1 is a highly abundant mitochondrial protein capable to bind an iron-sulfur cluster (ISC) in vitro using glutathione (GSH) as cofactor. We here report on the functional and structural analysis of 1-C-Grx1 in relation to its ISC-binding properties.
  
  
  RESULTS
  An N-terminal extension unique to 1-C-Grx1 from trypanosomatids affects the oligomeric structure and the ISC-binding capacity of the protein. The active-site Cys104 is essential for ISC binding, and the parasite-specific glutathionylspermidine and trypanothione can replace GSH as the ligands of the ISC. Interestingly, trypanothione forms stable protein-free ISC species that in vitro are incorporated into the dithiol T. brucei 2-C-Grx1, but not 1-C-Grx1. Overexpression of the C104S mutant of 1-C-Grx1 impairs disease progression in a mouse model. The structure of the Grx-domain of 1-C-Grx1 was solved by nuclear magnetic resonance spectroscopy. Despite the fact that several residues--which in other 1-C-Grxs are involved in the noncovalent binding of GSH--are conserved, different physicochemical approaches did not reveal any specific interaction between 1-C-Grx1 and free thiol ligands.
  
  
  METHODS
  Parasite Grxs are able to coordinate an ISC formed with trypanothione, suggesting a new mechanism of ISC binding and a novel function for the parasite-specific dithiol. The first 3D structure and in vivo relevance of a 1-C-Grx from a pathogenic protozoan are reported.
  
  
  CONCLUSIONS
  T. brucei 1-C-Grx1 is indispensable for mammalian parasitism and utilizes a new mechanism for ISC binding.
authors.affiliation: Laboratory Redox Biology of Trypanosomes, Institut Pasteur de Montevideo, Montevideo, Uruguay.
authors.forename: Bruno
authors.initials: B
authors.lastname: Manta
authors.forename: Carlo
authors.initials: C
authors.lastname: Pavan
authors.forename: Mattia
authors.initials: M
authors.lastname: Sturlese
authors.forename: Andrea
authors.initials: A
authors.lastname: Medeiros
authors.forename: Martina
authors.initials: M
authors.lastname: Crispo
authors.forename: Carsten
authors.initials: C
authors.lastname: Berndt
authors.forename: R Luise
authors.initials: RL
authors.lastname: Krauth-Siegel
authors.forename: Massimo
authors.initials: M
authors.lastname: Bellanda
authors.forename: Marcelo A
authors.initials: MA
authors.lastname: Comini
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D020134:Catalytic Domain; D003067:Coenzymes / Q000737:chemistry; D016384:Consensus Sequence; D003545:Cysteine / Q000737:chemistry; D005260:Female; D054477:Glutaredoxins / Q000737:chemistry; D005978:Glutathione / Q000737:chemistry; D007506:Iron-Sulfur Proteins / Q000737:chemistry; D051379:Mice; D008807:Mice, Inbred BALB C; D008928:Mitochondria / Q000201:enzymology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D018512:Parasitemia / Q000469:parasitology; D011485:Protein Binding; D017433:Protein Structure, Secondary; D015800:Protozoan Proteins / Q000737:chemistry; D014346:Trypanosoma brucei brucei / Q000201:enzymology* / Q000472:pathogenicity; D014353:Trypanosomiasis, African / Q000469:parasitology
chemical_list: D003067:Coenzymes; D054477:Glutaredoxins; D007506:Iron-Sulfur Proteins; D015800:Protozoan Proteins; D005978:Glutathione; D003545:Cysteine