|
|
|
|
|
|
|
||
* Department of Molecular Genetics, Kumamoto University School of Medicine, Kumamoto 862, Japan; and DnaJ homologues function in cooperation
with hsp70 family members in various cellular processes including intracellular protein trafficking and
folding. Three human DnaJ homologues present in the
cytosol have been identified: dj1 (hsp40/hdj-1), dj2
(HSDJ/hdj-2), and neuronal tissue-specific hsj1. dj1 is
thought to be engaged in folding of nascent polypeptides, whereas functions of the other DnaJ homologues
remain to be elucidated. To investigate roles of dj2 and
dj1, we developed a system of chaperone depletion
from and readdition to rabbit reticulocyte lysates. Using this system, we found that heat shock cognate 70 protein (hsc70) and dj2, but not dj1, are involved in mitochondrial import of preornithine transcarbamylase.
Bacterial DnaJ could replace mammalian dj2 in mitochondrial protein import. We also tested the effects of
these DnaJ homologues on folding of guanidine-denatured firefly luciferase. Unexpectedly, dj2, but not dj1,
together with hsc70 refolded the protein efficiently. We
propose that dj2 is the functional partner DnaJ homologue of hsc70 in the mammalian cytosol. Bacterial
DnaJ protein could replace mammalian dj2 in the refolding of luciferase. Thus, the cytosolic chaperone system for mitochondrial protein import and for protein
folding is highly conserved, involving DnaK and DnaJ
in bacteria, Ssa1-4p and Ydj1p in yeast, and hsc70 and
dj2 in mammals.
Institut für
Biochemie und Molekularbiologie, D-79104 Freiburg, Germany
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
This article has been cited by other articles:
|
|
