title: Homologs of the yeast Sec complex subunits Sec62p and Sec63p are abundant proteins in dog pancreas microsomes.
abstract: Cotranslational protein transport into dog pancreas microsomes involves the Sec61p complex plus a luminal heat shock protein 70. Posttranslational protein transport into the yeast endoplasmic reticulum (ER) involves the so-called Sec complex in the membrane, comprising a similar Sec61p subcomplex, the putative signal peptide receptor subcomplex, and the heat shock protein 40-type subunit, Sec63p, plus a luminal heat shock protein 70. Recently, human homologs of yeast proteins Sec62p and Sec63p were discovered. Here we determined the concentrations of these two membrane proteins in dog pancreas microsomes and observed that the canine homologs of yeast proteins Sec62p and Sec63p are abundant proteins, present in almost equimolar concentrations as compared with Sec61alphap monomers. Furthermore, we detected fractions of these two proteins in association with each other as well as with the Sec61p complex. The J domain of the human Sec63p was shown to interact with immunoglobulin heavy chain binding protein. Thus, the membrane of the mammalian ER contains components, known from the posttranslationally operating protein translocase in yeast. We suggest that these components are required for efficient cotranslational protein transport into the mammalian ER as well as for other transport processes.
authors.affiliation: Medizinische Biochemie und Molekularbiologie, Universität des Saarlandes, D-66421 Homburg, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Tyedmers
authors.forename: M
authors.initials: M
authors.lastname: Lerner
authors.forename: C
authors.initials: C
authors.lastname: Bies
authors.forename: J
authors.initials: J
authors.lastname: Dudek
authors.forename: M H
authors.initials: MH
authors.lastname: Skowronek
authors.forename: I G
authors.initials: IG
authors.lastname: Haas
authors.forename: N
authors.initials: N
authors.lastname: Heim
authors.forename: W
authors.initials: W
authors.lastname: Nastainczyk
authors.forename: J
authors.initials: J
authors.lastname: Volkmer
authors.forename: R
authors.initials: R
authors.lastname: Zimmermann
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D004285:Dogs; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism*; D006360:Heat-Shock Proteins; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism*; D026901:Membrane Transport Proteins; D008861:Microsomes / Q000378:metabolism*; D008969:Molecular Sequence Data; D010179:Pancreas / Q000378:metabolism* / Q000648:ultrastructure; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid
chemical_list: D005656:Fungal Proteins; D006360:Heat-Shock Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C074213:SEC62 protein, S cerevisiae; C074215:SEC63 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins