A. De Crouy-chanel et al., Interaction of DnaK with native proteins and membrane proteins correlates with their accessible hydrophobicity, GENE, 230(2), 1999, pp. 163-170
Molecular chaperones are involved in protein folding, protein targeting to
membranes, and protein renaturation after stress. They interact specificall
y with hydrophobic sequences that are exposed in unfolded proteins, and bur
ied in native proteins. We have studied the interaction of DnaK with native
water-soluble proteins and membrane proteins. DnaK-native protein interact
ions are characterized by dissociation constants between 1 and 50 mu M (com
pared with 0.01-1 mu M for unfolded proteins). This affinity is within the
range of most intracellular protein concentrations, suggesting that DnaK in
teracts with a greater number of native proteins than previously suspected.
We found a correlation between the affinity of native proteins for DnaK an
d their affinity for hydrophobic-interaction chromatography adsorbents, sug
gesting that DnaK interacts with exposed hydrophobic groups in native prote
ins. The interaction between DnaK and membrane proteins is characterized by
DnaK's high affinity for detergent-solubilized membrane proteins, and its
lower affinity for membrane proteins inserted in lipid bilayers, suggesting
that the chaperone can interact with the hydrophobic sequences of the form
er, while it cannot penetrate the hydrophobic core of lipid bilayers. Thus,
the specificity of DnaK for hydrophobic sequences is involved in its inter
action with not only unfolded proteins, but also native water-soluble prote
ins and membrane proteins. All proteins interact with DnaK according to the
ir exposed hydrophobicity. (C) 1999 Elsevier Science B.V. All rights reserv
ed.