title: Structures of the iron-sulfur flavoproteins from Methanosarcina thermophila and Archaeoglobus fulgidus.
abstract: Iron-sulfur flavoproteins (ISF) constitute a widespread family of redox-active proteins in anaerobic prokaryotes. Based on sequence homologies, their overall structure is expected to be similar to that of flavodoxins, but in addition to a flavin mononucleotide cofactor they also contain a cubane-type [4Fe:4S] cluster. In order to gain further insight into the function and properties of ISF, the three-dimensional structures of two ISF homologs, one from the thermophilic methanogen Methanosarcina thermophila and one from the hyperthermophilic sulfate-reducing archaeon Archaeoglobus fulgidus, were determined. The structures indicate that ISF assembles to form a tetramer and that electron transfer between the two types of redox cofactors requires oligomerization to juxtapose the flavin mononucleotide and [4Fe:4S] cluster bound to different subunits. This is only possible between different monomers upon oligomerization. Fundamental differences in the surface properties of the two ISF homologs underscore the diversity encountered within this protein family.
authors.affiliation: Institut für Mikrobiologie und Genetik, Abt. Molekulare Strukturbiologie, Georg-August-Universität Göttingen, Justus-von-Liebig-Weg 11, 37077 Göttingen, Germany.
authors.forename: Susana L A
authors.initials: SL
authors.lastname: Andrade
authors.forename: Francisco
authors.initials: F
authors.lastname: Cruz
authors.forename: Catherine L
authors.initials: CL
authors.lastname: Drennan
authors.forename: Vijay
authors.initials: V
authors.lastname: Ramakrishnan
authors.forename: Douglas C
authors.initials: DC
authors.lastname: Rees
authors.forename: James G
authors.initials: JG
authors.lastname: Ferry
authors.forename: Oliver
authors.initials: O
authors.lastname: Einsle
mesh_terms: D000595:Amino Acid Sequence; D019611:Archaeoglobus fulgidus / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D003460:Crystallization; D005420:Flavoproteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D007501:Iron / Q000737:chemistry* / Q000378:metabolism; D017020:Methanosarcina / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013455:Sulfur / Q000737:chemistry* / Q000378:metabolism
chemical_list: D005420:Flavoproteins; D013455:Sulfur; D007501:Iron