title: Structural organization of essential iron-sulfur clusters in the evolutionarily highly conserved ATP-binding cassette protein ABCE1.
abstract: The ABC protein ABCE1, formerly named RNase L inhibitor RLI1, is one of the most conserved proteins in evolution and is expressed in all organisms except eubacteria. Because of its fundamental role in translation initiation and/or ribosome biosynthesis, ABCE1 is essential for life. Its molecular mechanism has, however, not been elucidated. In addition to two ABC ATPase domains, ABCE1 contains a unique N-terminal region with eight conserved cysteines, predicted to coordinate iron-sulfur clusters. Here we present detailed information on the type and on the structural organization of the Fe-S clusters in ABCE1. Based on biophysical, biochemical, and yeast genetic analyses, ABCE1 harbors two essential diamagnetic [4Fe-4S](2+) clusters with different electronic environments, one ferredoxin-like (CPX(n)CX(2)CX(2)C; Cys at positions 4-7) and one unique ABCE1-type cluster (CXPX(2)CX(3)CX(n)CP; Cys at positions 1, 2, 3, and 8). Strikingly, only seven of the eight conserved cysteines coordinating the Fe-S clusters are essential for cell viability. Mutagenesis of the cysteine at position 6 yielded a functional ABCE1 with the ferredoxin-like Fe-S cluster in a paramagnetic [3Fe-4S](+) state. Notably, a lethal mutation of the cysteine at position 4 can be rescued by ligand swapping with an adjacent, extra cysteine conserved among all eukaryotes.
authors.affiliation: Institute of Biochemistry, Biocenter, Johann Wolfgang Goethe University, Max-von-Laue-Strasse 9, D-60439 Frankfurt am Main, Germany.
authors.forename: Dominik
authors.initials: D
authors.lastname: Barthelme
authors.forename: Urte
authors.initials: U
authors.lastname: Scheele
authors.forename: Stephanie
authors.initials: S
authors.lastname: Dinkelaker
authors.forename: Adam
authors.initials: A
authors.lastname: Janoschka
authors.forename: Fraser
authors.initials: F
authors.lastname: Macmillan
authors.forename: Sonja-Verena
authors.initials: SV
authors.lastname: Albers
authors.forename: Arnold J M
authors.initials: AJ
authors.lastname: Driessen
authors.forename: Marco Salamone
authors.initials: MS
authors.lastname: Stagni
authors.forename: Eckhard
authors.initials: E
authors.lastname: Bill
authors.forename: Wolfram
authors.initials: W
authors.lastname: Meyer-Klaucke
authors.forename: Volker
authors.initials: V
authors.lastname: Schünemann
authors.forename: Robert
authors.initials: R
authors.lastname: Tampé
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D003545:Cysteine / Q000737:chemistry / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D019143:Evolution, Molecular; D005288:Ferredoxins / Q000737:chemistry / Q000378:metabolism; D005816:Genetic Complementation Test; D007501:Iron / Q000737:chemistry*; D007506:Iron-Sulfur Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D012441:Saccharomyces cerevisiae; D017386:Sequence Homology, Amino Acid; D013056:Spectrophotometry, Ultraviolet; D015204:Spectroscopy, Mossbauer; D048229:Sulfolobus solfataricus / Q000235:genetics / Q000378:metabolism; D013455:Sulfur / Q000737:chemistry*
chemical_list: D018528:ATP-Binding Cassette Transporters; D005288:Ferredoxins; D007506:Iron-Sulfur Proteins; D013455:Sulfur; D007501:Iron; D003545:Cysteine