Ceruloplasmin: macromolecular assemblies with iron-containing acute phase proteins

• Published in: PloS one 2013-07, Vol.8 (7), p.e67145-e67145
• Main Authors: Samygina, Valeriya R, Sokolov, Alexey V, Bourenkov, Gleb, Petoukhov, Maxim V, Pulina, Maria O, Zakharova, Elena T, Vasilyev, Vadim B, Bartunik, Hans, Svergun, Dmitri I
• Format: Article
• Language: English
• Subjects: Acute phase proteins; Acute phase substances; Acute-Phase Proteins - chemistry; Acute-Phase Proteins - metabolism; Analysis; Antimicrobial agents; Antioxidants; Automation; Biology; Ceruloplasmin; Ceruloplasmin - chemistry; Ceruloplasmin - metabolism; Coordination compounds; Copper; Crystal structure; Crystallography, X-Ray; Damage prevention; Data analysis; Ferroxidase; Humans; Inflammation; Inflammatory diseases; Iron; Iron - chemistry; Iron - metabolism; Lactoferrin; Lactoferrin - chemistry; Lactoferrin - metabolism; Lobes; Macromolecules; Medicine; Models, Molecular; Multiprotein Complexes - chemistry; Multiprotein Complexes - metabolism; Oxidation; Pathogenesis; Peroxidase; Peroxidase - chemistry; Peroxidase - metabolism; Phenylenediamine; Physics; Proteases; Protein Binding; Protein Conformation; Protein interaction; Protein Interaction Domains and Motifs; Protein-protein interactions; Proteins; Small angle X ray scattering; Solutions; Stoichiometry; Substrates; X ray scattering; X-ray diffraction
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0067145

Copper-containing ferroxidase ceruloplasmin (Cp) forms binary and ternary complexes with cationic proteins lactoferrin (Lf) and myeloperoxidase (Mpo) during inflammation. We present an X-ray crystal structure of a 2Cp-Mpo complex at 4.7 Å resolution. This structure allows one to identify major protein-protein interaction areas and provides an explanation for a competitive inhibition of Mpo by Cp and for the activation of p-phenylenediamine oxidation by Mpo. Small angle X-ray scattering was employed to construct low-resolution models of the Cp-Lf complex and, for the first time, of the ternary 2Cp-2Lf-Mpo complex in solution. The SAXS-based model of Cp-Lf supports the predicted 1:1 stoichiometry of the complex and demonstrates that both lobes of Lf contact domains 1 and 6 of Cp. The 2Cp-2Lf-Mpo SAXS model reveals the absence of interaction between Mpo and Lf in the ternary complex, so Cp can serve as a mediator of protein interactions in complex architecture. Mpo protects antioxidant properties of Cp by isolating its sensitive loop from proteases. The latter is important for incorporation of Fe(3+) into Lf, which activates ferroxidase activity of Cp and precludes oxidation of Cp substrates. Our models provide the structural basis for possible regulatory role of these complexes in preventing iron-induced oxidative damage.