2qcw | pdb_00002qcw
Crystal Structure of Bone Morphogenetic Protein-6 (BMP-6)
Structural highlights
Function[BMP6_HUMAN] Induces cartilage and bone formation. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedBone 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 approximately 1.8 microM but ActRIIb with 30-fold higher affinity at Kd approximately 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. BMP-3 and BMP-6 structures illuminate the nature of binding specificity with receptors.,Allendorph GP, Isaacs MJ, Kawakami Y, Belmonte JC, Choe S Biochemistry. 2007 Oct 30;46(43):12238-47. Epub 2007 Oct 9. PMID:17924656[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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