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.
Biophys Chem. 2010 Nov;152(1-3):99-108. doi: 10.1016/j.bpc.2010.08.005. Epub 2010 Aug 17.
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.
XIAP-BIR3 结构域阻断了凋亡途径的大部分内容，是新型抗癌药物的一个有吸引力的靶标。来自蛋白 Smac/DIABLO 的四肽 AVPI 与 XIAP-BIR3 结构域结合，使癌细胞死亡。在这里，我们描述了 AVPI 与 XIAP-BIR3 的结合参数，并分析了它对该结构域热力学稳定性的影响。XIAP-BIR3 对物理和化学处理具有异常的稳定性，并且通过与 AVPI 的相互作用变得更加稳定。核磁共振实验表明，构象选择发生在 AVPI 与 XIAP-BIR3 的相互作用过程中。分子动力学模拟证实，XIAP-BIR3 的灵活性显著降低。与结合过程中构象熵损失相关的正结合熵表明，疏水相互作用在相互作用和结构域稳定中起着重要作用。讨论了 XIAP-BIR3 稳定的机制及其对药物亲和力优化的影响。
