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The membrane proteins TRAMp and sec61αp may be involved in post‐translational transport of presecretory proteins into mammalian microsomes
Author(s) -
Klappa Peter,
Zimmermann Maria,
Zimmermann Richard
Publication year - 1994
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(94)80473-7
Subject(s) - microsome , membrane protein , transport protein , chemistry , biochemistry , membrane transport , trypsin , translation (biology) , membrane , enzyme , messenger rna , gene
The presecretory protein ppcecDHFR, a hybrid between preprocecropinA and dihydrofolate reductase, is transported into mammalian microsomes post‐translationally, i.e. independent of ribosome and signal recognition particle. Here, the involvement of microsomal proteins in ribonucleoparticle‐independent transport of ppcecDHFR was analyzed by transport into trypsin‐pretreated microsomes and by transport of a truncated version of ppcecDHFR and subsequent chemical cross‐linking. We observed that post‐translational transport of ppcecDHFR can occur into microsomes which had been pretreated with trypsin (final concentration, 100μg/ml) and that of the known transport components only TRAMp and sec61αp are still present under these conditions. Furthermore, we found that the truncated ppcecDHFR, ppcecDHFR‐98mer′, can be cross‐linked to 36 kDa microsomal membrane proteins during post‐translational transport. Therefore, the two microsomal membrane proteins with molecular masses of about 36 kDa, TRAMp and secolαp, appear to be involved in the post‐translational transport of ppcecDHFR and ppcecDHFR‐98mer.