A novel type of co-chaperone mediates transmembrane recruitment of DnaK-like chaperones to ribosomes.
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.
Dudek
Johanna
J
Medizinische Biochemie und Molekularbiologie, Physiologie, Anatomie and Zellbiologie, Universität des Saarlandes, D-66421 Homburg, Germany.
Volkmer
Jörg
J
Bies
Christiane
C
Guth
Silvia
S
Müller
Anika
A
Lerner
Monika
M
Feick
Peter
P
Schäfer
Karl-Herbert
KH
Morgenstern
Eberhard
E
Hennessy
Fritha
F
Blatch
Gregory L
GL
Janoscheck
Katja
K
Heim
Nicole
N
Scholtes
Petra
P
Frien
Michael
M
Nastainczyk
Wolfgang
W
Zimmermann
Richard
R
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
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