Bs. Vallee et al., Behaviour of bovine phosphatidylethanolamine-binding protein with model membranes - Evidence of affinity for negatively charged membranes, EUR J BIOCH, 268(22), 2001, pp. 5831-5841
The ability of phosphatidylethanolamine-binding protein (PEBP) to bind memb
ranes was tested by using small and large unilamellar vesicles and monolaye
rs composed Of L-alpha -1,2-dimyristoylphosphatidylcholine, L-alpha -1,2-di
myristoylphosphatidylglycerol and L-alpha -1,2-dimyristoylphosphatidylethan
olamine. PEBP only bound to model membranes containing L-alpha -1,2-dimyris
toylphosphatidylglycerol; the interaction was primarily due to electrostati
c forces between the basic protein and the acidic phospholipids. Further ex
periments indicated that the interaction was not dependent on the length an
d unsaturation of the phospholipid acyl chains and was not modified by the
presence of cholesterol in the membrane. PEBP affinity for negatively charg
ed membranes is puzzling considering the previous identification of the pro
tein as a phosphatidylethanolamine-binding protein, and suggests that the a
ssociation of PEBP with phospholipid membranes is driven by a mechanism oth
er than its binding to solubilized phosphatidylethanolamine. An explanation
was suggested by its three-dimensional structure: a small cavity at the pr
otein surface has been reported to be the binding site of the polar head of
phosphatidylethanolamine, while the N-terminal and C-terminal parts of PEB
P, exposed at the protein surface, appear to be involved in the interaction
with membranes. To test this hypothesis, we synthesized the two PEBP termi
nal regions and tested them with model membranes in parallel with the whole
protein. Both peptides displayed the same behaviour as whole PEBP, indicat
ing that they could participate in the binding of PEBP to membranes. Our re
sults strongly suggest that PEBP directly interacts with negatively charged
membrane microdomains in living cells.