title: Structural model of haptoglobin and its complex with the anticoagulant ecotin variants: structure-activity relationship study and analysis of interactions.
abstract: Recently the literature described the binding of Haptoglobin (HP) with ecotin, a fold-specific serine-proteases inhibitor with an anticoagulant profile and produced by Escherichia coli. In this work, we used some in silico and in vitro techniques to evaluate HP 3D-fold and its interaction with wild-type ecotin and two variants. Our data showed HP models conserved trypsin fold, in agreement to the in vitro immunological recognition of HP by trypsin antibodies. The analysis of the three ecotin-HP complexes using the mutants RR and TSRR/R besides the wild type revealed several hydrogen bonds between HP and ecotin secondary site. These data are in agreement with the in vitro PAGE assays that showed the HP-RR complex in native gel conditions. Interestingly, the ternary complex interactions varied depending on the inhibitor structure and site-directed mutation. The interaction of HP with TSRR/R involved new residues compared to wild type, which infers a binding energy increase caused by the mutation.
authors.affiliation: Program of Post-graduation in Pathology, Antônio Pedro University Hospital and.
authors.forename: Plínio Cunha
authors.initials: PC
authors.lastname: Sathler
authors.forename: André Luiz
authors.initials: AL
authors.lastname: Lourenço
authors.forename: Leonardo Alves
authors.initials: LA
authors.lastname: Miceli
authors.forename: Carlos Rangel
authors.initials: CR
authors.lastname: Rodrigues
authors.forename: Magaly Girão
authors.initials: MG
authors.lastname: Albuquerque
authors.forename: Lúcio Mendes
authors.initials: LM
authors.lastname: Cabral
authors.forename: Helena Carla
authors.initials: HC
authors.lastname: Castro
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000925:Anticoagulants / Q000737:chemistry*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics; D006242:Haptoglobins / Q000737:chemistry* / Q000235:genetics; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D033903:Periplasmic Proteins / Q000737:chemistry* / Q000235:genetics; D011485:Protein Binding; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D057057:Serine Proteases / Q000737:chemistry* / Q000235:genetics; D013329:Structure-Activity Relationship; D013552:Swine
chemical_list: D000925:Anticoagulants; C039076:Eco protein, E coli; D029968:Escherichia coli Proteins; C485359:HP protein, human; D006242:Haptoglobins; D033903:Periplasmic Proteins; D057057:Serine Proteases