BMP-3 and BMP-6 structures illuminate the nature of binding specificity with receptors
BMP-3 and BMP-6 structures illuminate the nature of binding specificity with receptors
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DOI：
10.1021/bi700907k
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发表时间：
2007-10-30
期刊：
影响因子：
2.9
通讯作者：
Choe, Senyon
中科院分区：
文献类型：
--
作者：
Allendorph, George P.;Isaacs, Michael J.;Choe, Senyon
骨形态发生蛋白（BMPs）是细胞外信使配体，参与控制一系列发育和细胞间信号传导过程。为了启动它们特定的细胞内信号通路，配体识别并结合两种结构相关的丝氨酸/苏氨酸激酶受体，称为I型和type。11、在细胞表面。在这里，我们介绍了BMP-3和BMP-6的晶体结构，其中BMP-3在其受体身份、亲和力和特异性方面仍然知之甚少。通过表面等离子体共振（BIAcore），我们发现BMP-3与激活素受体11型（ActRII）结合的K-d约为1.8 M-mu，而与ActRIIb结合的K-d约为53 nM，亲和力高30倍。这种对ActRII的低亲和力可能涉及BMP-3的Ser-28和Asp-33，它们仅存在于BMP-3的11型受体结合界面中。任何残基对丙氨酸的点突变导致对任一受体的亲和力提高20倍。我们进一步通过基于smad的全细胞荧光素酶实验证明，BMP-3（S28A）对ActRII亲和力的增加使配体的信号传导能力达到与BMP-6相当的水平。关注BMP-3对ActRIIb的偏好，我们发现ActRII的Lys-76和ActRIIb的结构等效的Glu-76在两种受体之间是不同的。我们发现ActRllb（E76K）和ActRII以相似的亲和力结合BMP-3，表明BMP-3受体特异性受BMP-3的Lys-30与ActRIIb的Glu-76的相互作用控制。这些研究阐明了单个氨基酸如何调节配体-受体结合的特异性，并可能改变体内的生物信号传导和功能。
Bone morphogenetic proteins (BMPs) are extracellular messenger ligands involved in controlling a wide array of developmental and intercellular signaling processes. To initiate their specific intracellular signaling pathways, the ligands recognize and bind two structurally related serine/threonine kinase receptors, termed type I and type. 11, on the cell surface. Here, we present the crystal structures of BMP-3 and BMP-6, of which BMP-3 has remained poorly understood with respect to its receptor identity, affinity, and specificity. Using surface plasmon resonance (BIAcore) we show that BMP-3 binds Activin Receptor type 11 (ActRII) with K-d approximate to zz 1.8 M-mu but ActRIIb with 30-fold higher affinity at K-d approximate to 53 nM. This low affinity for ActRII may involve Ser-28 and Asp-33 of BMP-3, which are found only in BMP-3's type 11 receptor-binding interfaces. Point mutations of either residue to alanine results in up to 20-fold higher affinity to either receptor. We further demonstrate by Smad-based whole cell luciferase assays that the increased affinity of BMP-3(S28A) to ActRII enables the ligand's signaling ability to a level comparable to that of BMP-6. Focusing on BMP-3's preference for ActRIIb, we find that Lys-76 of ActRII and the structurally equivalent Glu-76 of ActRIIb are distinct between the two receptors. We demonstrate that ActRllb(E76K) and ActRII bind BMP-3 with similar affinity, indicating BMP-3 receptor specificity is controlled by the interaction of Lys-30 of BMP-3 with Glu-76 of ActRIIb. These studies illustrate how a single amino acid can regulate the specificity of ligand-receptor binding and potentially alter biological signaling and function in vivo.