State Key Laboratory for Supramolecular Structure and Materials, Jilin University, No. 2699, Qianjin Street, Changchun 130012 China.
J Phys Chem B. 2010 Dec 2;114(47):15656-62. doi: 10.1021/jp1036603. Epub 2010 Nov 9.
Survivin, as an apoptosis suppressor, exists as a homodimer interfacing at the N-terminal portion (residues 6-13) of its baculovirus IAP repeat (BIR) domain and a linker segment (residues 89-102). Here we expressed full-length human Survivin (SurF) and a series of its mutants, SurΔN7, SurΔN13, and SurΔN18 with significant truncations of the N-terminus, all of which could still dimerize in solution. Single-molecule force spectroscopy (SMFS) was used to quantitate the unbinding forces of full-length and the mutant homodimers and revealed that the N-terminal residues up to Arg18 were not essential for dimerization. Meanwhile, the binding of SurΔN7 to Smac/DIABLO determined by ELISA was as efficient as the wild-type, but that of SurΔN13 was significantly reduced, and that of SurΔN18 was completely lost. Together, these findings provide direct evidence that the N-terminal sequence of Survivin is not critical for dimer formation but may contribute to correct folding and function of BIR.
Survivin 作为一种凋亡抑制因子，以同源二聚体的形式存在，其 N 端部分（残基 6-13）与杆状病毒 IAP 重复（BIR）结构域和连接片段（残基 89-102）相互作用。在这里，我们表达了全长人 Survivin（SurF）和一系列突变体，SurΔN7、SurΔN13 和 SurΔN18，它们的 N 端有明显的截断，但仍能在溶液中形成二聚体。单分子力谱（SMFS）用于定量全长和突变体同源二聚体的解链力，结果表明，N 端的残基到 Arg18 对二聚化不是必需的。同时，ELISA 法测定的 SurΔN7 与 Smac/DIABLO 的结合与野生型一样有效，但 SurΔN13 的结合显著降低，SurΔN18 的结合完全丧失。这些发现共同提供了直接证据，表明 Survivin 的 N 端序列对二聚体形成不是关键的，但可能有助于 BIR 的正确折叠和功能。
