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.
Mesh Terms:
Amino Acid Sequence, Animals, Dogs, Escherichia coli Proteins, HSP40 Heat-Shock Proteins, HSP70 Heat-Shock Proteins, Heat-Shock Proteins, Mice, Microsomes, Models, Biological, Molecular Chaperones, Molecular Sequence Data, Neoplasm Proteins, Pancreas, Protein Biosynthesis, Protein Structure, Tertiary, Recombinant Fusion Proteins, Ribosomes, Sequence Alignment
EMBO J.
Date: Jun. 17, 2002
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