Eckelman B P, Drag M, Snipas S J, Salvesen G S
Program in Apoptosis and Cell Death Research, Burnham Institute for Medical Research, La Jolla, CA 92037, USA
Cell Death Differ. 2008 May;15(5):920-8. doi: 10.1038/cdd.2008.6. Epub 2008 Feb 1.
We describe the peptide-binding specificity of the baculoviral IAP repeat (BIR) domains of the human inhibitor of apoptosis (IAP) proteins, X-linked IAP, cellular IAP1 and neuronal apoptosis inhibitory protein (NAIP). Synthetic peptide libraries were used to profile each domain, and we distinguish two types of binding specificity, which we refer to as type II and type III BIR domains. Both types have a dominant selectivity for Ala in the first position of the four N-terminal residues of the peptide ligands, which constitute a core recognition motif. Our analysis allows us to define the signature of type III BIRs that demonstrate a preference for Pro in the third residue of the ligand, resembling the classic IAP-binding motif (IBM). The signature of the type II BIRs was similar to type III, but with a striking absence of specificity for Pro in the third position, suggesting that the definition of an IBM must be modified depending on the type of BIR in question. These findings explain how subtle changes in the peptide-binding groove of IAP BIR domains can significantly alter the target protein selectivity. Our analysis allows for prediction of BIR domain protein-binding preferences, provides a context for understanding the mechanism of peptide selection and heightens our knowledge of the specificity of IAP antagonists that are being developed as cancer therapeutics.
我们描述了人类凋亡抑制蛋白（IAP）家族成员X连锁IAP、细胞IAP1和神经元凋亡抑制蛋白（NAIP）的杆状病毒IAP重复序列（BIR）结构域的肽结合特异性。利用合成肽文库对每个结构域进行分析，我们区分出两种结合特异性，分别称为II型和III型BIR结构域。这两种类型对肽配体N端四个残基中第一个位置的丙氨酸都有显著选择性，这四个残基构成一个核心识别基序。我们的分析使我们能够定义III型BIR的特征，其对配体第三个残基中的脯氨酸有偏好，类似于经典的IAP结合基序（IBM）。II型BIR的特征与III型相似，但在第三个位置对脯氨酸明显缺乏特异性，这表明必须根据所讨论的BIR类型修改IBM的定义。这些发现解释了IAP BIR结构域肽结合凹槽中的细微变化如何能显著改变靶蛋白选择性。我们的分析有助于预测BIR结构域的蛋白结合偏好，为理解肽选择机制提供背景，并加深我们对作为癌症治疗药物正在开发的IAP拮抗剂特异性的认识。
