title: Structural and metal binding characterization of the C-terminal metallochaperone domain of membrane fusion protein SilB from Cupriavidus metallidurans CH34.
abstract: Detoxification of heavy metal ions in Proteobacteria is tightly controlled by various systems regulating their sequestration and transport. In Cupriavidus metallidurans CH34, a model organism for heavy metal resistance studies, the sil determinant is potentially involved in the efflux of silver and copper ions. Proteins SilA, SilB, and SilC form a resistance nodulation cell division (RND)-based transport system in which SilB is the periplasmic adaptor protein belonging to the membrane fusion protein (MFP) family. In addition to the four domains typical of known MFPs, SilB has a fifth additional C-terminal domain, called SilB(440-521), which is characterized here. Structure and backbone dynamics of SilB(440-521) have been investigated using nuclear magnetic resonance, and the residues of the metal site were identified from (15)N- and (13)C-edited HSQC spectra. The solution structure and additional metal binding experiments demonstrated that this C-terminal domain folds independently of the rest of the protein and has a conformation and a Ag(+) and Cu(+) binding specificity similar to those determined for CusF from Escherichia coli. The small protein CusF plays a role in metal trafficking in the periplasm. The similarity with CusF suggests a potential metallochaperone role for SilB(440-521) that is discussed in the context of simultaneous expression of different determinants involved in copper resistance in C. metallidurans CH34.
authors.affiliation: CNRS, Institut de Biologie Structurale Jean-Pierre Ebel, Grenoble, France.
authors.forename: Beate
authors.initials: B
authors.lastname: Bersch
authors.forename: Kheiro-Mouna
authors.initials: KM
authors.lastname: Derfoufi
authors.forename: Fabien
authors.initials: F
authors.lastname: De Angelis
authors.forename: Vanessa
authors.initials: V
authors.lastname: Auquier
authors.forename: Elisabeth Ngonlong
authors.initials: EN
authors.lastname: Ekendé
authors.forename: Max
authors.initials: M
authors.lastname: Mergeay
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Ruysschaert
authors.forename: Guy
authors.initials: G
authors.lastname: Vandenbussche
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D001665:Binding Sites; D003300:Copper / Q000378:metabolism; D049921:Cupriavidus; D050576:Membrane Fusion Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D056511:Metallochaperones / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D008670:Metals / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D012834:Silver / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D050576:Membrane Fusion Proteins; D056511:Metallochaperones; D008670:Metals; D010446:Peptide Fragments; D012834:Silver; D003300:Copper