Figure 2. High-molecular-weight forms of SIBLING proteins in teeth and crosslinking by TG-Western blot analysis. (A) DPP polymers are present in the G2-extract. (B) DSPP, precursor protein for DPP and DSP, is found only in the E-extract. (C) Purified DPP forms polymers in vitro after TG2 incubation. (D) TG2 is found in HMW forms after incubation with DPP, indicating that it can serve as a crosslinking partner for DPP. (E) DMP1 polymers are found in both E- and G2-extracts. (F) Polymer formation of DMP1 after incubation with TG2, and bPA incorporation into DMP1 after TG2 incubation. (G) DSP is found only in monomeric forms in the E-extract. (H) DSP forms polymers and incorporates bPA when incubated with TG2. (I) BSP ‘dimers’ are found in both the E- and G2-extracts; similar-sized BSP forms are also found in rat and mouse bone E-extracts.