Permeability of the Peroxisomal Membrane

Abstract

Purified peroxisomes are permeable to sucrose and to a variety of other small molecules, including the cofactors NAD, CoA, ATP and carnitine. The permeability of the organelles is not mediated by the presence of a number of specific translocases, since cofactor diffusion into isolated peroxisomes was rapid even at low temperature, not saturable and not inhibited by analogs. Reconstitution of the peroxisomal integral membrane protein fraction into liposomes made the vesicles permeable to sucrose and to other molecules that entered the intact organelle. Separation of the integral membrane proteins on sucrose density gradients and reconstitution of the gradient fractions into liposomes suggested that the permeabilizing activity resides with a 22 kDa integral membrane protein. The observations indicate that the permeability of the peroxisomal membrane to small water-soluble molecules is based on the presence of a nonselective poreforming protein.

The observation indicate that the permeability of the peroxisomal membrane to small water souluble molecules is based on the presence of a nonselective pore forming protein.