Figure 1. Summary of Chordin, Tsg and Tolloid Regulation of BMP Signalling.

(A) Schematic diagram of the domain layout of full-length chordin with the larger fragments produced by tolloid cleavage indicated. (B) Model showing the mechanism of BMP regulation by chordin. BMP binds to chordin in an inhibitory complex, which is strengthened in the presence of Tsg. Following cleavage of chordin by tolloids at both sites, Tsg competes with the residual fragments for binding to BMP and is thought to increase the rate of fragment turnover.