Noncovalent complexes of transforming growth factor-β family growth/differentiation factors with their prodomains are classified as latent or active, depending on whether the complexes can bind their respective receptors. For the anti-Müllerian hormone (AMH), the hormone-prodomain complex is active, and the prodomain is displaced upon binding to its type II receptor, AMH receptor type-2 (AMHR2), on the cell surface. However, the mechanism by which this displacement occurs is unclear. Here, we used ELISA assays to measure the dependence of prodomain displacement on AMH concentration and analyzed results with respect to the behavior expected for reversible binding in combination with ligand-induced receptor dimerization. We found that, in solution, the prodomain has a high affinity for the growth factor (GF) (Kd = 0.4 pM). Binding of the AMH complex to a single AMHR2 molecule does not affect this Kd and does not induce prodomain displacement, indicating that the receptor binding site in the AMH complex is fully accessible to AMHR2. However, recruitment of a second AMHR2 molecule to bind the ligand bivalently leads to a 1000-fold increase in the Kd for the AMH complex, resulting in rapid release of the prodomain. Displacement occurs only if the AMHR2 is presented on a surface, indicating that prodomain displacement is caused by a conformational change in the GF induced by bivalent binding to AMHR2. In addition, we demonstrate that the bone morphogenetic protein 7 prodomain is displaced from the complex with its GF by a similar process, suggesting that this may represent a general mechanism for receptor-mediated prodomain displacement in this ligand family.

中文翻译：

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在与激素受体二价结合后，抗苗勒管激素前结构域从激素/前结构域复合物中置换出来。

转化生长因子-β家族生长/分化因子与其前结构域的非共价复合物被分类为潜在的或活性的，这取决于复合物是否可以结合它们各自的受体。对于抗苗勒管激素 (AMH)，激素-前结构域复合物是有活性的，前结构域在与细胞表面的 II 型受体、AMH 受体 2 型 (AMHR2) 结合后被置换。然而，这种位移发生的机制尚不清楚。在这里，我们使用 ELISA 测定来测量前结构域置换对 AMH 浓度的依赖性，并分析了与配体诱导的受体二聚化相结合的可逆结合预期行为的结果。我们发现，在溶液中，前结构域对生长因子 (GF) 具有高亲和力 (Kd = 0.4 pM)。AMH 复合物与单个 AMHR2 分子的结合不会影响该 Kd 并且不会诱导前结构域置换，这表明 AMH 复合物中的受体结合位点对 AMHR2 是完全可接近的。然而，招募第二个 AMHR2 分子以二价结合配体导致 AMH 复合物的 Kd 增加 1000 倍，从而导致前结构域的快速释放。只有当 AMHR2 出现在表面上时才会发生位移，这表明前结构域位移是由与 AMHR2 的二价结合诱导的 GF 构象变化引起的。此外，我们证明骨形态发生蛋白 7 前结构域通过类似的过程从具有其 GF 的复合物中置换出来，这表明这可能代表了该配体家族中受体介导的前结构域置换的一般机制。