A novel type of co-chaperone mediates transmembrane recruitment of DnaK-like chaperones to ribosomes |
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Authors: | Dudek Johanna Volkmer Jörg Bies Christiane Guth Silvia Müller Anika Lerner Monika Feick Peter Schäfer Karl-Herbert Morgenstern Eberhard Hennessy Fritha Blatch Gregory L Janoscheck Katja Heim Nicole Scholtes Petra Frien Michael Nastainczyk Wolfgang Zimmermann Richard |
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Institution: | Medizinische Biochemie und Molekularbiologie, Physiologie, Anatomie and Zellbiologie, Universit?t des Saarlandes, D-66421 Homburg, Germany. |
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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. |
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