Tissue transglutaminase catalyzes the deamidation of glutamines in lens betaB(2)- and betaB(3)-crystallins.
Tissue transglutaminase (tTG) is a Ca(2+)-dependent enzyme catalyzing the formation of covalent crosslinks between peptide-bound glutamine and lysine residues. Lens crystallins, including alphaB-crystallin and several beta-crystallins, are in vitro substrates for tTG. In both human and bovine fetal lens extracts treated with commercially available guinea pig liver tTG we detected the formation of high molecular weight (HMW) aggregates containing crosslinked betaB(2)- and betaA(3)-crystallin. More interestingly, 2D-gel electrophoresis combined with mass spectrometry analysis revealed that glutamines present in the N-terminal arms of betaB(2)- and betaB(3)-crystallins deamidate readily in the presence of tTG. We found that both tTG-catalyzed crosslinking and deamidation disrupt the beta-crystallin complex, suggesting that these tTG-catalyzed modifications can influence the macromolecular assembly of lens crystallins. These data together suggest that tTG can contribute to the age-related deamidation of glutamine residues of lens crystallins.
Boros
Sandor
S
Department of Biomolecular Chemistry 271, Nijmegen Center for Molecular Life Sciences, Radboud University, Nijmegen, The Netherlands.
Wilmarth
Phillip A
PA
Kamps
Bram
B
de Jong
Wilfried W
WW
Bloemendal
Hans
H
Lampi
Kirsten
K
Boelens
Wilbert C
WC
D000375:Aging / Q000378:metabolism; D000577:Amides / Q000378:metabolism; D000818:Animals; D002384:Catalysis; D002417:Cattle; D005333:Fetus / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000494:pharmacology*; D005973:Glutamine / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D007908:Lens, Crystalline / Q000187:drug effects* / Q000196:embryology / Q000378:metabolism; D008875:Middle Aged; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D020543:Proteome / Q000187:drug effects; D011503:Transglutaminases / Q000494:pharmacology*; D038206:beta-Crystallin B Chain / Q000378:metabolism*
D000577:Amides; C103908:CRYBB3 protein, human; D020543:Proteome; D038206:beta-Crystallin B Chain; C113634:beta-crystallin B2; D005973:Glutamine; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011503:Transglutaminases; D019204:GTP-Binding Proteins