title: A novel type of co-chaperone mediates transmembrane recruitment of DnaK-like chaperones to ribosomes.
abstract: Recently, the homolog of yeast protein Sec63p was identified in dog pancreas microsomes. This pancreatic DnaJ-like protein was shown to be an abundant protein, interacting with both the Sec61p complex and lumenal DnaK-like proteins, such as BiP. The pancreatic endoplasmic reticulum contains a second DnaJ-like membrane protein, which had been termed Mtj1p in mouse. Mtj1p is present in pancreatic microsomes at a lower concentration than Sec63p but has a higher affinity for BiP. In addition to a lumenal J-domain, Mtj1p contains a single transmembrane domain and a cytosolic domain which is in close contact with translating ribosomes and appears to have the ability to modulate translation. The interaction with ribosomes involves a highly charged region within the cytosolic domain of Mtj1p. We propose that Mtj1p represents a novel type of co-chaperone, mediating transmembrane recruitment of DnaK-like chaperones to ribosomes and, possibly, transmembrane signaling between ribosomes and DnaK-like chaperones of the endoplasmic reticulum.
authors.affiliation: Medizinische Biochemie und Molekularbiologie, Physiologie, Anatomie and Zellbiologie, Universität des Saarlandes, D-66421 Homburg, Germany.
authors.forename: Johanna
authors.initials: J
authors.lastname: Dudek
authors.forename: Jörg
authors.initials: J
authors.lastname: Volkmer
authors.forename: Christiane
authors.initials: C
authors.lastname: Bies
authors.forename: Silvia
authors.initials: S
authors.lastname: Guth
authors.forename: Anika
authors.initials: A
authors.lastname: Müller
authors.forename: Monika
authors.initials: M
authors.lastname: Lerner
authors.forename: Peter
authors.initials: P
authors.lastname: Feick
authors.forename: Karl-Herbert
authors.initials: KH
authors.lastname: Schäfer
authors.forename: Eberhard
authors.initials: E
authors.lastname: Morgenstern
authors.forename: Fritha
authors.initials: F
authors.lastname: Hennessy
authors.forename: Gregory L
authors.initials: GL
authors.lastname: Blatch
authors.forename: Katja
authors.initials: K
authors.lastname: Janoscheck
authors.forename: Nicole
authors.initials: N
authors.lastname: Heim
authors.forename: Petra
authors.initials: P
authors.lastname: Scholtes
authors.forename: Michael
authors.initials: M
authors.lastname: Frien
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Nastainczyk
authors.forename: Richard
authors.initials: R
authors.lastname: Zimmermann
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D004285:Dogs; D029968:Escherichia coli Proteins; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics* / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D051379:Mice; D008861:Microsomes / Q000378:metabolism; D008954:Models, Biological; D018832:Molecular Chaperones / Q000378:metabolism*; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D010179:Pancreas / Q000166:cytology / Q000378:metabolism; D014176:Protein Biosynthesis; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism*; D016415:Sequence Alignment
chemical_list: C092319:Dnajc1 protein, mouse; D029968:Escherichia coli Proteins; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D009363:Neoplasm Proteins; D011993:Recombinant Fusion Proteins; C063842:dnaK protein, E coli