title: Crystal structure of Escherichia coli SufA involved in biosynthesis of iron-sulfur clusters: implications for a functional dimer.
abstract: IscA and SufA are paralogous proteins that play crucial roles in the biosynthesis of Fe-S clusters, perhaps through a mechanism involving transient Fe-S cluster formation. We have determined the crystal structure of E. coli SufA at 2.7A resolution. SufA exists as a homodimer, in contrast to the tetrameric organization of IscA. Furthermore, a C-terminal segment containing two essential cysteine residues (Cys-Gly-Cys), which is disordered in the IscA structure, is clearly visible in one molecule (the alpha1 subunit) of the SufA homodimer. Although this segment is disordered in the other molecule (the alpha2 subunit), computer modeling of this segment based on the well-defined conformation of alpha1 subunit suggests that the four cysteine residues (Cys114 and Cys116 in each subunit) in the Cys-Gly-Cys motif are positioned in close proximity at the dimer interface. The arrangement of these cysteines together with the nearby Glu118 in SufA dimer may allow coordination of an Fe-S cluster and/or an Fe atom.
authors.affiliation: Department of Biology, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan.
authors.forename: Kei
authors.initials: K
authors.lastname: Wada
authors.forename: Yuko
authors.initials: Y
authors.lastname: Hasegawa
authors.forename: Zhao
authors.initials: Z
authors.lastname: Gong
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Minami
authors.forename: Keiichi
authors.initials: K
authors.lastname: Fukuyama
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Takahashi
mesh_terms: D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000737:chemistry* / Q000502:physiology; D018360:Crystallography, X-Ray; D019281:Dimerization; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000502:physiology; D007501:Iron / Q000737:chemistry; D015394:Molecular Structure; D011485:Protein Binding; D011487:Protein Conformation; D016415:Sequence Alignment; D013455:Sulfur / Q000737:chemistry
chemical_list: D002352:Carrier Proteins; D029968:Escherichia coli Proteins; C499169:SufA protein, E coli; D013455:Sulfur; D007501:Iron