492
Chaperones, Molecular
1
1
Heat or other
stress
2
3
Aggregated or
misfolded protein
Folded protein
4
Folded protein with
ligand bound
Lipid bilayer
Partially folded
protein
2
Ribosome
Nascent polypeptide
chain
Fig. 1
The general roles of molecular
chaperones. Molecular chaperones are involved
in many different cellular processes, including
protection of nascent proteins on the ribosome
(1); folding of newly synthesized or newly
membrane-translocated proteins (2); protection
and refolding of misfolded, partially unfolded, or
aggregated proteins (such as after heat shock
(3); and maintenance of proteins in a partially
unfolded state (4) for binding effectors or
crossing membranes. Other roles are discussed
further in the text.
eukaryotic cells
have to
be modifed
beFore leaving the endoplasmic reticulum
(ER), and molecular chaperones play an
important role here in quality control,
ensuring that only those proteins with
the correct modifcations proceed Further
down the pathway. ┬▒inally, proteins are
not particularly stable entities, and hence
have a propensity to unFold under certain
nonoptimal conditions such as a small
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