Transglutaminase-1 (TGM1) and involucrin (IVL) are expressed shortly after envoplakin and periplakin. TGM1 associates with the plasma membrane via C14-16 fatty-acid adducts on its C-terminus (Steinert et al. 1996). IVL deposition precedes that of most other cornified envelope proteins (Nemes & Steinert 1999). It can bind the plasma membrane in a calcium and phosphatidyl-serine dependent manner, where it becomes a substrate for membrane-bound TGM1 and TGM5 (Nemes et al. 1999, Candi et al. 2001).