Fig. 9: Trans dimerization of the PAPP-A dimer is maintained in the PAPP-A·STC2 structure. | Nature Communications

Fig. 9: Trans dimerization of the PAPP-A dimer is maintained in the PAPP-A·STC2 structure.

From: Structure of the proteolytic enzyme PAPP-A with the endogenous inhibitor stanniocalcin-2 reveals its inhibitory mechanism

Fig. 9

a Minimalistic schematic drawing of the PAPP-A·STC2 2:2 complex with indication of the intersubunit disulfide bonds (vertical gray bars) and observed (C domain-STC2) and hypothesized (LNR1-STC2) interactions (blue lines). The LNR modules are shown in green. Note that because the PAPP-A polypeptides cross at M6, LNR1 and LNR3 of each PAPP-A subunit do not interact with the same STC2 subunit. b Biochemical experiments have shown that PAPP-A subunits truncated before LNR3 are able to form dimers, but such dimers cannot cleave IGFBP-418. c Heterodimerization between the same subunit truncated before LNR3 and a C-terminal fragment of PAPP-A, which is truncated before M5, rescues the proteolytic activity toward IGFBP-418, thus suggesting that PAPP-A is configured in trans before it forms the complex with STC2.

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