title: Lys-17 is the amine-donor substrate site for transglutaminase in beta A3-crystallin.
abstract: The bovine lens protein beta A3-crystallin has recently been shown to be an amine-donor (Lys) substrate for tissue-type transglutaminase, using a newly developed amine-acceptor hexapeptide as a probe (Groenen, P.J.T.A., Seccia, M., Smulders, R.H.P.H., Gravela, E., Cheeseman, K.H., Bloemendal, H., and de Jong, W.W. (1993) Biochem. J. 295, 399-404). In the present study, the reactive amine-donor site has been identified by site-directed mutagenesis of the putative substrate lysine. The mutation Lys-17-->Arg abolishes the substrate capacity. This residue, located in the N-terminal extension of the polypeptide, thus acts as the sole amine-donor substrate in beta A3-crystallin. Our finding reinforces the notion that, in the crystallins, all amine-donor as well as amine-acceptor substrate sites reside in the N- or C-terminal arms. Transglutaminase-mediated cross-linking of beta A3-crystallin also gives rise to a beta A3 dimer, presumably due to the fact that Lys-17 can be cross-linked to the previously established Gln-7 or Gln-8 amine-acceptor site.
authors.affiliation: Department of Biochemistry, University of Nijmegen, The Netherlands.
authors.forename: P J
authors.initials: PJ
authors.lastname: Groenen
authors.forename: J J
authors.initials: JJ
authors.lastname: Grootjans
authors.forename: N H
authors.initials: NH
authors.lastname: Lubsen
authors.forename: H
authors.initials: H
authors.lastname: Bloemendal
authors.forename: W W
authors.initials: WW
authors.lastname: de Jong
mesh_terms: D000818:Animals; D001483:Base Sequence; D002417:Cattle; D003459:Crystallins / Q000737:chemistry / Q000378:metabolism*; D017931:DNA Primers / Q000737:chemistry; D008239:Lysine / Q000737:chemistry; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D051381:Rats; D011994:Recombinant Proteins; D013329:Structure-Activity Relationship; D011503:Transglutaminases / Q000378:metabolism*
chemical_list: D003459:Crystallins; D017931:DNA Primers; D011994:Recombinant Proteins; D011503:Transglutaminases; D008239:Lysine