A tetrameric complex of membrane proteins in the endoplasmic reticulum

Eur J Biochem. 1993 Jun 1;214(2):375-81. doi: 10.1111/j.1432-1033.1993.tb17933.x.


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 (alpha and beta subunits). We now show that TRAP complex is actually comprised of four membrane proteins (alpha, beta, gamma, delta), 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 delta subunit spans the membrane only once and has its major portion, containing a disulfide bridge, at the lumenal side. The gamma subunit is predicted to span the membrane four times.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Calcium-Binding Proteins*
  • Cloning, Molecular
  • DNA / chemistry
  • DNA / genetics
  • Dogs
  • Endoplasmic Reticulum / chemistry*
  • Macromolecular Substances
  • Membrane Glycoproteins / chemistry*
  • Membrane Glycoproteins / genetics
  • Molecular Sequence Data
  • Receptors, Cell Surface / chemistry*
  • Receptors, Cell Surface / genetics
  • Receptors, Cytoplasmic and Nuclear*
  • Receptors, Peptide*


  • Calcium-Binding Proteins
  • Macromolecular Substances
  • Membrane Glycoproteins
  • Receptors, Cell Surface
  • Receptors, Cytoplasmic and Nuclear
  • Receptors, Peptide
  • signal sequence receptor
  • DNA

Associated data

  • GENBANK/D14868
  • GENBANK/L09679
  • GENBANK/L09680
  • GENBANK/L09681
  • GENBANK/L09682
  • GENBANK/L09683
  • GENBANK/X57950
  • GENBANK/X71000
  • GENBANK/Z14030
  • GENBANK/Z19087