title: Conformational selection, dynamic restriction and the hydrophobic effect coupled to stabilization of the BIR3 domain of the human X-linked inhibitor of apoptosis protein by the tetrapeptide AVPI.
abstract: The XIAP-BIR3 domain blocks a substantial portion of the apoptosis pathway and is an attractive target for novel anticancer agents. The tetrapeptide AVPI, from the protein Smac/DIABLO, binds to the XIAP-BIR3 domain, allowing the cancer cells to die. Here we characterize the binding parameters of AVPI to XIAP-BIR3 and analyze its effects on the thermodynamic stability of this domain. XIAP-BIR3 was exceptionally stable against physical and chemical treatments and became even more stable by interaction with AVPI. Nuclear magnetic resonance experiments demonstrated that conformational selection is taking place upon AVPI interaction with XIAP-BIR3. Molecular dynamics simulations corroborate that the flexibility of XIAP-BIR3 is significantly reduced. The positive binding entropy associated with a loss of conformational entropy involved in the binding indicates that hydrophobic interactions play an important role in the interaction and domain stabilization. The mechanism of XIAP-BIR3 stabilization and its implications for drug affinity optimization are discussed.
authors.affiliation: Programa de Biologia Estrutural and Centro Nacional de Ressonância Magnética Nuclear de Macromoléculas, Instituto de Bioquímica Médica, Instituto Nacional de Ciência e Tecnologia de Biologia Estrutural e Bioimagem, INBEB, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, 21941-902, Brazil.
authors.forename: Theo Luiz Ferraz
authors.initials: TL
authors.lastname: de Souza
authors.forename: Daniel
authors.initials: D
authors.lastname: Sanches
authors.forename: Rafael Braga
authors.initials: RB
authors.lastname: Gonçalves
authors.forename: Samuel Silva
authors.initials: SS
authors.lastname: da RochaPita
authors.forename: Pedro Geraldo
authors.initials: PG
authors.lastname: Pascutti
authors.forename: M Lucia
authors.initials: ML
authors.lastname: Bianconi
authors.forename: Fabio Ceneviva Lacerda
authors.initials: FC
authors.lastname: de Almeida
authors.forename: Jerson L
authors.initials: JL
authors.lastname: Silva
authors.forename: Andréa Cheble
authors.initials: AC
authors.lastname: de Oliveira
mesh_terms: D000595:Amino Acid Sequence; D017209:Apoptosis; D002152:Calorimetry, Differential Scanning; D002942:Circular Dichroism; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D056004:Molecular Dynamics Simulation; D009842:Oligopeptides / Q000737:chemistry*; D011485:Protein Binding; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D013050:Spectrometry, Fluorescence; D013816:Thermodynamics; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000737:chemistry* / Q000378:metabolism
chemical_list: D009842:Oligopeptides; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human