Human bone morphogenetic protein-2 (BMP2) plays an important role in the development of bone and cartilage, which functions as bone growth factor by interacting with its cognate type-I and type-II receptors (BMPR-I and BMPR-II) through conformational wrist epitope and linear knuckle epitope, respectively. Here, the intermolecular interaction between the BMP2 knuckle epitope and BMPR-II is investigated at structural level, from which a binding hotspot region is identified that is primarily responsible for the epitope recognition by BMPR-II. A KEH peptide covering the hotspot region exhibits a weak binding affinity (K_d = 78.6 ± 13.5 µM) to BMPR-II and a moderate osteogenic activity on human BMSCs (ALP = 135 ± 17% and 164 ± 21% at peptide concentrations 0.01 and 0.1 µg/ml, respectively). Quantitative structure-activity relationship (QSAR) is used to guide the rational optimization of KEH peptide. The strategy focuses on systematic design of the peptide’s non-key residues to derive a series of its promising mutants, which are then evaluated rigorously by using dynamics simulation and energetic analysis. Consequently, totally ten designed peptide mutants are tested in vitro at molecular and cellular levels; most of them are determined to exhibit an increased or comparable affinity/activity relative to the native KEH peptide and knuckle epitope. In particular, the KEH-p7 peptide is found to have a satisfactory profile with K_d = 9.6 ± 1.2 µM and ALP = 178 ± 24% and 235 ± 32% at peptide concentrations 0.01 and 0.1 µg/ml, respectively. Structural analysis reveals a complicated noncovalent network of hydrogen bonds, hydrophobic forces and stacking interactions across the complex interface of BMPR-II with KEH-p7, conferring both stability and specificity to the receptor–peptide interaction.

人骨形态发生蛋白2（BMP2）在骨骼和软骨的发育中起着重要作用，它通过与其同源的I型和II型受体（BMPR-I和BMPR-II）相互作用，作为骨骼生长因子构型腕表位和线性指关节表位。在此，从结构水平研究了BMP2指关节表位与BMPR-II之间的分子间相互作用，从中确定了一个结合热点区域，该区域主要负责BMPR-II识别表位。覆盖热点区域的KEH肽显示出较弱的结合亲和力（K _d对BMPR-II的抑制作用为78.6±13.5 µM）和对人BMSC的中等成骨活性（肽浓度为0.01和0.1 µg / ml时ALP分别为135±17％和164±21％）。定量构效关系（QSAR）用于指导KEH肽的合理优化。该策略着重于对肽的非关键残基进行系统设计，以衍生出一系列有前途的突变体，然后通过动力学模拟和能量分析对其进行严格评估。因此，总共在分子和细胞水平上测试了十个设计好的肽突变体。相对于天然KEH肽和指关节表位，它们中的大多数被确定表现出增加的或相当的亲和力/活性。特别地，发现KEH-p7肽具有令人满意的K _d谱。当肽浓度为0.01和0.1 µg / ml时，分别为9.6±1.2 µM和ALP = 178±24％和235±32％。结构分析揭示了一个复杂的氢键，疏水力和跨BMPR-II与KEH-p7的复杂界面的堆积相互作用的非共价网络，为受体-肽相互作用赋予了稳定性和特异性。