Xenbase Image ID: 116374

Figure 9. Model for EGF-CFC, Activin Receptors, Lefty, and TGFβ Interactions(A) In the absence of ligands, the EGF-CFC coreceptor (solid pink) is constitutively bound to the type I receptor Alk4 (solid green).(B) Nodal (solid blue) binds to receptor complexes consisting of EGF-CFC/Alk4 and ActRIIB (solid green).(C) Lefty (solid yellow) sequesters the EGF-CFC coreceptor, thereby preventing Nodal binding to the receptor complexes.(D) Subtle sequence differences determine the interaction with the EGF-CFC coreceptor and the Lefty inhibitor. Nodal and Vg1/GDF1 (solid blue) require the EGF-CFC coreceptor for signaling through ActRIIB and Alk4, while Activin (solid red) does not. SqtActβB[loopβ8] and Vg1ActβB[loopβ8] (solid blue with red strip) containing the loop-β8 region of ActivinβB can bind to ActRIIB and Alk4 without the EGF-CFC coreceptor and therefore cannot be blocked by Lefty. ActSqt[Finger1-loopβ8] (solid red with two blue strips) requires the coreceptor for receptor complex binding and can be inhibited by Lefty. Image published in: Cheng SK et al. (2004) Copyright: ©2004 Cheng et al. This image is reproduced with permission of the journal and the copyright holder. This is an open-access article distributed under the terms of the Creative Commons Attribution license Larger Image Printer Friendly View

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