A tetrameric complex of membrane proteins in the endoplasmic reticulum

Enno HARTMANN, Dirk GÖRLICH, Susanne KOSTKA, Albrecht OTTO, Regine KRAFT, Signe KNESPEL, Elke BÜRGER, Tom A. RAPOPORT*, Siegfried PREHN

*Corresponding author for this work
100 Citations (Scopus)


The translocation site (translocon), at which nascent polypeptides pass through the endoplasmic reticulum membrane, contains a component previously called ‘signal sequence receptor’ that is now renamed as ‘translocon‐associated protein’ (TRAP). Two glycosylated subunits of the TRAP complex have been identified before (α and β subunits). We now show that the TRAP complex is actually comprised of four membrane proteins (α, β, γ, δ), present in a stoichiometric relation, which are genuine neighbours in intact microsomes. The amino acid sequences of the additional, non‐glycosylated subunits were deduced from cloning of the corresponding cDNAs. The δ subunit spans the membrane only once and has its major portion, containing a disulfide bridge, at the lumenal side. The γ subunit is predicted to span the membrane four times.

Original languageEnglish
JournalEuropean Journal of Biochemistry
Issue number2
Pages (from-to)375-381
Number of pages7
Publication statusPublished - 01.01.1993


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