BMP-3 and BMP-6 structures illuminate the nature of binding specificity with receptors

George P. Allendorph, Michael J. Isaacs, Yasuhiko Kawakami, Juan Carlos Izpisua Belmonte, Senyon Choe

Research output: Contribution to journalArticle

78 Scopus citations

Abstract

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 II, 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 II (ActRII) with Kd ≈ 1.8 μM but ActRIIb with 30-fold higher affinity at Kd ≈ 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 II 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-3S28A 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 ActRIIbE76K 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.

Original languageEnglish (US)
Pages (from-to)12238-12247
Number of pages10
JournalBiochemistry
Volume46
Issue number43
DOIs
StatePublished - Oct 30 2007

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    Allendorph, G. P., Isaacs, M. J., Kawakami, Y., Belmonte, J. C. I., & Choe, S. (2007). BMP-3 and BMP-6 structures illuminate the nature of binding specificity with receptors. Biochemistry, 46(43), 12238-12247. https://doi.org/10.1021/bi700907k