Restricted endogenous proteolysis of myelin basic protein of zinc-treated myelin

Isolated myelin of bovine spinal cord was saturated with 500 mu ZnCl2 to immobilize myelin basic protein (MBP) and to assess the degradation of endogenous or exogenous MBP by neutral proteinase activity of myelin. While the initial degradation of endogenous MBP was not affected by Zn2+ a single fragment of approximately 17kDa accumulated in zinc-treated myelin as compared to several fragments in the control. In contrast exogenous MBP was fully degraded even by zinc-saturated myelin. In immobilizing MBP zinc appears to limit the access of endogenous proteinases to a terminal portion of the primary structure of myelin-associated MBP.