[Substrates of ADP-ribosyltransferase of human erythrocytes]

Incubation of human erythrocyte membranes with [32P]NAD resulted in the label incorporation into the 37 kDa and 41 kDa proteins as determined by SDS-PAAG electrophoresis with subsequent autoradiography. Treatment of labeled membranes with HgCl2 caused a significant decrease of the protein band intensity in the autoradiograms. Incubation of purified GTP-binding protein from rat brain (Go-protein) with membranes and erythrocyte cytoplasm in the presence of [32P]NAD resulted in the label incorporation into the Go-protein alpha-subunit. This incorporation was markedly decreased after treatment of radiolabeled Go-protein with HgCl2. The data obtained testify to the existence in human erythrocytes of cytoplasmic and membrane-bound forms of cysteine-specific ADP-ribosyl transferase, for which the Go-protein serves as a substrate. The 37 kDa and 41 kDa proteins are substrates for the membrane-bound form of the enzyme.