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. Author manuscript; available in PMC: 2014 Aug 6.
Published in final edited form as: Structure. 2013 Aug 6;21(8):10.1016/j.str.2013.07.015. doi: 10.1016/j.str.2013.07.015

Figure 1. The malleability of the cystine knot growth factor fold.

Figure 1

(a) Dimeric forms of the cystine-knotted signaling proteins, BMP-2 and VEGF-C, and the BMP antagonists, PRDC and noggin. Disulfide bonds that form the cystine knot, as well as those that form the inter-chain disulfide(s) in BMP-2, VEGF-C, and noggin, are depicted using a ball- and-stick representation. Asterisks on the PRDC structure designate the BMP binding site as identified through site-directed mutagenesis and accompanying functional studies. (b) Monomeric forms of the cystine-knotted signaling proteins and the BMP antagonists shown in panel a (shown also is the BMP antagonist SOST). Disulfide bonds that form the cystine knot are depicted using a ball-and-stick representation as in panel a.