Figure 1. Transglutaminase (TG) activity and protein substrates in tooth EDTA extracts. (A) Western blotting TG-activity assay; 5(biotin)pentylamine (bPA) labeling of tooth substrates by endogenous TG in tooth EDTA extract (E). bPA incorporation is detected by ExtrAvidin^®-HRP conjugate and occurs in proteins having molecular weights of 60 and 80 kDa, and high-molecular-weight material above 150 kDa. The band at 100 kDa in the last lane represents TG2 itself, which autolabels in the crosslinking reaction. (B) Purification of bPA-labeled material by avidin chromatography and detection of BSP and DMP1 in the preparation by Western blotting with anti-BSP and anti-DMP1 antibodies; N-terminal sequencing gave the DPP sequence Asp-Asp-Pro-Asn. EAvid, ExtrAvidin^®-HRP conjugate.