In: THE JOURNAL OF CELL BIOLOGY , 87 (1980), S. 503-508

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Abstract

When rough microsomes are subjected to limited proteolysis and high salt, a soluble fraction can be separated from the membrane . Neither fraction alone is capable of vectorially translocating nascent peptides . When the soluble extract is recombined with the residual membrane fraction, translocating activity is restored . Standard biochemical techniques were used to identify and characterize the active component derived by treating rough microsomes with elastase and high salt. The active factor is a peptide fragment with an apparent molecular weight of 60,000. It represents the cytoplasmic domain of a larger membrane protein. The fragment is basic and has at least one accessible sulfhydryl group. These characteristics facilitated its purification and identification as a membrane component required for translocation of nascent peptides across microsomal membranes.