Vibrio cholerae Hemolysin Implication of Amphiphilicity and Lipid-Induced Conformational Change for its Pore-forming Activity
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Vibrio cholerae Hemolysin
Implication of Amphiphilicity and Lipid-Induced Conformational Change
for its Pore-forming Activity
Banerjee, Kalyan K
Structural Biology & Bioinformatics
Vibrio cholerae hemolysin (HlyA), a water-soluble protein
with a native monomeric relative molecular mass of 65 000,
forms transmembrane pentameric channels in target biomembranes.
T heHlyA binds to lipid vesicles nonspecifically
and without saturation; however, self-assembly is triggered
specifically by cholesterol.Here we show that the HlyA
partitioned quantitatively to amphiphilic media irrespective
of their compositions, indicating that the toxin had an
amphiphilic surface.Asialofe tuin, a b1-galactosyl-terminated
glycoprotein, which binds specifically to the HlyA in a
lectin-glycoprotein type of interaction and inhibits carbohydrate-
independent interaction of the toxin with lipid,
reduced effective amphiphilicity of the toxin significantly.
Resistance of the HlyA to proteases together with the tryptophan
fluorescence emission spectrum suggested a compact
structure for the toxin.Fluorescence energy transfer from the
HlyA to dansyl-phosphatidylethanolamine required the presence of cholesterol in the lipid bilayer and was
synchronous with oligomerization.Phospholipid bilayer
without cholesterol caused a partial unfolding of the HlyA
monomer as indicated by the transfer of tryptophan residues
from the nonpolar core of the protein to amore polar region.
These observations suggested: (a) partitioning of the HlyA to
lipid vesicles is driven by the tendency of the amphiphilic
toxin to reduce energetically unfavorable contacts with water
and is not affected significantly by the composition of the
vesicles; and (b) partial unfolding of the HlyA at the lipid–
water interface precedes and promotes cholesterol-induced
oligomerization to an insertion-competent configuration.
Chattopadhyay, Kausik and Bhattacharyya, Debasish and Banerjee, Kalyan K (2002) Vibrio cholerae Hemolysin Implication of Amphiphilicity and Lipid-Induced Conformational Change for its Pore-forming Activity. European Journal Of Biochemistry, 269 (17). pp. 4351-4358.