Probing the transglutaminase-mediated, posttranslational modification of proteins during development

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Abstract
Sphaerechinus granularis eggs were fertilized in seawater in the presence of 0.2 mM dansylcadaverine, and development was allowed to take place with this compound in the medium. .gamma.-Glutamyldansylcadaverine, indicative of the utilization of the amine tracer by intrinsic transglutaminase, was isolated from the embryonic proteins, and identity of the product with the chemically synthesized .gamma.-glutamyl derivative of dansylcadaverine was confirmed. Covalent labeling of proteins occurring during development was examined by means of electrophoresis in NaDodSO4, followed by immunoblotting with an antibody that specifically recognized that dansyl hapten. There was an increase in the total uptake of the trace at an esssentially constant rate with each cell division, from 2- to 8- and 64-cell stages. Moreover, multiple protein labelling was evident in all specimens. The described concept of studying posttranslational modifications in vivo by transglutaminase through detection of the haptenic or specific ligand recognizable group of an incorporated small amine substrate will undoubtedly be of general utility for probing the function of this family of enzymes in other cell types as well.