496
Chaperones, Molecular
Tab. 1
(
continued
)
Name
of
family
Prokaryotic
examples
Eukaryotic
examples
Cellular
location
Known
cochaperones
Cellular functions
Hsp90
HtpG
Cytosol
Unknown, heatshock induced, but dispensable
Hsp90
Cytosol
Hop, FKBP51,
p23
Binding to proteins that require activation with ligand
such as steroid hormone, protection against heat
shock? Also buffers against genetic variation.
Grp94
ER
Unknown, probably a role in quality control of protein
transport
TRAP1
Mitochondria
Unknown
Hsp100
ClpB
Cytosol
Works with DnaK to dissipate protein aggregates
Hsp104
Cytosol
Works with Hsp70 to dissipate protein aggregates
sHSPs
IbpA, IbpB
Cytosol
Probably act to hold denatured proteins for other
chaperones to refold
Hsp25
Cytosol
Probably act to hold denatured proteins for other
chaperones to refold
α
-B-crystallin
Eye lens
Keep eye lens proteins in solution
Redox chaperones
DsbA/DsbC
Periplasm
Respectively introduce and isomerize disul±de bonds;
require DsbB and DsbD respectively to regenerate
active forms
Hsp33
Cytosol
Activated by oxidation, may protect proteins damaged
by oxidation in cytosol
Protein disul±de
isomerase
ER
Introduce and isomerize disul±de bonds; requires
Ero1 to regenerate active form
ER chaperones
Calnexin,
calreticulin
ER
Act to prevent incorrectly glycosylated proteins from
entering the secretory pathway
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