A MEMBRANE-PROTEIN PRIMARILY ASSOCIATED WITH THE LYSOSOMAL COMPARTMENT

A monoclonal antibody designated MBR 39 has been generated against a m embrane associated protein found selectively on lysosomes. MBR 39 reac ts with the cytosolic face of the lysosome and was used to develop an organelle binding assay which reacted with high density organelles cha racteristic of lysosomes. These organelles contained lysosomal enzyme markers which included the integral membrane protein acetyl-CoA:alpha- glucosaminide N-acetyltransferase and the soluble lysosomal enzyme mar kers acid phosphatase (mature form), beta-hexosaminidase, arylsulfatas e, and alpha-L-iduronidase, Under conditions which disrupt lysosomes t he release of the latter soluble lysosomal enzymes was demonstrated fr om MBR 39 bound organelles. Immunoblots of MBR 39 with purified fibrob last lysosomal membrane, demonstrated reactivity with polypeptides of molecular mass 63 kDa (major species) and 73 kDa (minor species). (C) 1997 Elsevier Science B.V.