ADP-ribosyltransferase activity in myelin membranes isolated from human brain

An ADP-ribosyltransferase has been identified in compact myelin and in several white matter fractions which contain less compact myelin, fractionated on the basis of increasing protein/lipid ratios. One fraction the P(3)A contained the greatest activity although the activity in compact myelin was only slightly less. The ADP-ribosyltransferase activity of solubilized myelin was stimulated by increasing amounts of GTP gamma S and was specific for the beta-isomer of NAD. Although ADP-ribosylation was demonstrated with the heterotrimeric G proteins in the 40-50 kDa range, the substrate for the ADP-ribosyltransferase in the 20 kDa range was identified as MBP.