Participates in morphogenetic activities of the cells, maybe by stabilizing the membrane or subcortical structures of cells that are under mechanical stress. Probably catalyzes the cross-linking of proteins and the conjugation of polyamines to proteins. L-glutaminyl-[protein] + L-lysyl-[protein] = [protein]-L-lysyl-N(6)-5-L-glutamyl-[protein] + NH4(+) Binds 1 Ca(2+) ion per subunit. Intracellular and peripherally associated with the inner leaflet of the cell membrane, using a fatty acid linkage. Has an annular, or ring-like expression pattern in epithelial annuli of developing limb segment boundary cells. In embryos, it is seen in gastrulating cells, in cells surrounding rapidly dividing neuroblasts, and in muscle pioneer cells invaginating to form apodemes. Expression of this protein in embryos and limbs is associated with areas undergoing movements, morphogenetic rearrangements, or rapid cell division. Expression of annulin precedes the first morphological signs of segmentation in the developing limbs. Belongs to the transglutaminase superfamily. Transglutaminase family.