Figure 3.

Cleavage at the S2 site disrupts noncovalent association between the S1-cleaved prodomain and mature BMP-4. Epitope tagged wild-type or S2 cleavage mutant proBMP-4 was expressed in Xenopus oocytes. Cleavage products present in lysates or media were analyzed by probing immunoblots (IB) of total protein or α-myc immunoprecipitates (IP myc) with antibodies specific for HA- or myc-epitopes as indicated. The position of S1- or S2-cleaved prodomain and mature BMP-4 is illustrated schematically to the right.