Transglutaminase catalyzed incorporation of putrescine into surface proteins of mouse neuroblastoma cells.

Transglutaminase, purified from guinea pig liver, was used to catalyze the incorporation of [14C]putrescine into exposed surface proteins of intact mouse neuroblastoma cells. This method specifically labeled two surface proteins (Mr = 92 000 and 76 000) in the N-18 mouse neuroblastoma cells and three surface proteins (Mr = 92 000, 76 000, and 72 000) in the NB-15 mouse neuroblastoma cells. In addition, transglutaminase also catalyzed cross-linking reactions of exposed surface proteins. In both the N-18 and NB-15 cells, differentiation was accompanied by a 2-fold increase of specific radioactivity incorporated into trichloroacetic acid insoluble cellular material, suggesting that the differentiated mouse neuroblastoma cells may possess greater amount of accessible peptide-bound glutaminyl residues on their surface than their malignant counterparts. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorographic method revealed that while the [14C]putrescine-labeled protein patterns of undifferentiated and differentiated mouse neuroblastoma cells were similar, the intensity of labeling of individual bands was specifically modulated by cell differentiation.