title: Structural model of the CopA copper ATPase of Enterococcus hirae based on chemical cross-linking.
abstract: The CopA copper ATPase of Enterococcus hirae belongs to the family of heavy metal pumping CPx-type ATPases and shares 43% sequence similarity with the human Menkes and Wilson copper ATPases. Due to a lack of suitable protein crystals, only partial three-dimensional structures have so far been obtained for this family of ion pumps. We present a structural model of CopA derived by combining topological information obtained by intramolecular cross-linking with molecular modeling. Purified CopA was cross-linked with different bivalent reagents, followed by tryptic digestion and identification of cross-linked peptides by mass spectrometry. The structural proximity of tryptic fragments provided information about the structural arrangement of the hydrophilic protein domains, which was integrated into a three-dimensional model of CopA. Comparative modeling of CopA was guided by the sequence similarity to the calcium ATPase of the sarcoplasmic reticulum, Serca1, for which detailed structures are available. In addition, known partial structures of CPx-ATPase homologous to CopA were used as modeling templates. A docking approach was used to predict the orientation of the heavy metal binding domain of CopA relative to the core structure, which was verified by distance constraints derived from cross-links. The overall structural model of CopA resembles the Serca1 structure, but reveals distinctive features of CPx-type ATPases. A prominent feature is the positioning of the heavy metal binding domain. It features an orientation of the Cu binding ligands which is appropriate for the interaction with Cu-loaded metallochaperones in solution. Moreover, a novel model of the architecture of the intramembranous Cu binding sites could be derived.
authors.affiliation: Department of Biophysics, Ruhr-University Bochum, 44780, Bochum, Germany.
authors.forename: Mathias
authors.initials: M
authors.lastname: Lübben
authors.forename: Reto
authors.initials: R
authors.lastname: Portmann
authors.forename: Gerd
authors.initials: G
authors.lastname: Kock
authors.forename: Raphael
authors.initials: R
authors.lastname: Stoll
authors.forename: Malin M
authors.initials: MM
authors.lastname: Young
authors.forename: Marc
authors.initials: M
authors.lastname: Solioz
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000595:Amino Acid Sequence; D001665:Binding Sites; D027682:Cation Transport Proteins / Q000378:metabolism*; D000073840:Copper-Transporting ATPases; D003432:Cross-Linking Reagents / Q000737:chemistry / Q000494:pharmacology*; D016983:Enterococcus / Q000378:metabolism*; D013058:Mass Spectrometry / Q000379:methods; D019216:Metals, Heavy / Q000737:chemistry; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D027682:Cation Transport Proteins; D003432:Cross-Linking Reagents; D019216:Metals, Heavy; D010455:Peptides; D000251:Adenosine Triphosphatases; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000073840:Copper-Transporting ATPases