Nascent-polypeptide-associated Complex: A Bridge between Ribosome and Cytosol
- 1Department of Cell Biology, New York University School of Medicine, New York, New York 10016; 2Cellular Biochemistry and Biophysics Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10021; 3Molecular Biology Program, Cornell University, Graduate School of Medical Sciences, New York, New York 10021
This extract was created in the absence of an abstract.
Excerpt
The existence and elucidation of the secretory pathway was closely linked to the observation that a subset of ribosomes in the cell is not free in the cytoplasm but is bound to the endoplasmic reticulum (ER) membrane (for review, see Palade 1975). After it was shown that polypeptides synthesized on membrane-bound polysomes are vectorially discharged into the lumen of the ER (Redman and Sabatini 1966), efforts were made to separate, characterize, and then reconstitute the assembly of membrane-bound ribosomes and the formation of the ribosome-membrane junction in vitro (Adelman et al. 1973a,b; Blobel and Dobberstein 1975a,b; Siekevitz and Zemecnik 1981; Rapoport 1992; Gilmore 1993; Ng and Walter 1994; Sabatini and Adesnik 1995).
Since no apparent differences in the polypeptide compositions of these two classes of ribosomes were observed (Lewis and Sabatini 1977), it remained to be explained how the cell establishes and maintains these two classes of ribosomes. A solution...
