Translocation of a lysosomal enzyme across the microsomal membrane requires signal recognition particle

Abstract

Signal recognition particle (SRP), an 11S ribonucleoprotein (Walter and Blobel (1982) Nature 299, 691–698), is required for translocation of secretory proteins across microsomal membranes (Walter and Blobel (1980) Proc. Natl. Acad. Sci. USA 77, 7112–7116) and for asymmetric integration into microsomal membranes of a transmembrane protein (Anderson et al., (1982) J. Cell Biol. 93, 501–506). We demonstrate here that SRP is also required for translocation of the lysosomal protease cathepsin D across microsomal membranes.