SORTING-OUT OF ACCEPTOR DONOR RELATIONSHIPS IN THE TRANSGLUTAMINASE-CATALYZED CROSS-LINKING OF CRYSTALLINS BY THE ENZYME-DIRECTED LABELING OF POTENTIAL SITES

The dansyl-conjugated (Dns) peptides Dns-Pro-Gly-Gly-Gln-Gln-Ile-Val, and Dns-Ala-Gln-Gln-Ile-Val, patterned on the N-terminal sequence of fibronectin, were synthesized and used for the transglutaminase (protein-glutamine:amine gamma-glutamyltransferase, EC 2.3.2.13)-directed selective blocking of lens proteins that otherwise might participate in donating lysyl side chains in forming N-epsilon-(gamma-glutamyl)-lysine cross-linked oligomers and polymers. Labeling profiles with these peptides could be readily visualized by fluorescence as well as by immunoblotting with anti-dansyl antibody. The labeling patterns in rabbit lens homogenates were quite different with the dansylated peptides than those obtained with dansylcadaverine. Use of such glutamine-containing dansylated peptides should clearly aid in identifying, isolating, and sequencing potential donor substrates of transglutaminases in many biological systems.