Identification of a specific one amino acid change in recombinant human transglutaminase 2 that regulates its activity and calcium sensitivity

摘要: TG2 (transglutaminase 2) is a calcium-dependent protein cross-linking enzyme which involved in variety of cellular processes. The threshold level calcium needed for endogenous and recombinant activity has been controversial, the former being more sensitive to than latter. In present study we address this question by identifying single amino acid change from conserved valine glycine at position 224 compared with sequence available genomic databases. Substituting residue Gly224 increased its calcium-binding affinity transamidation 10-fold isopeptidase severalfold, explaining inactivity widely used physiological concentrations. ITC (isothermal titration calorimetry) measurements showed 7-fold higher affinities residues could be activated inside cells. two forms had comparable substrate- GTP-binding also bound fibronectin similarly, but coeliac antibodies residues. Structural analysis indicated stability decrease flexibility loop resulting improved metal-binding affinity. results suggest that Val224 increases modulating enabling reactions