R. Ishiguro et al., ORIENTATION OF FUSION-ACTIVE SYNTHETIC PEPTIDES IN PHOSPHOLIPID-BILAYERS - DETERMINATION BY FOURIER-TRANSFORM INFRARED-SPECTROSCOPY, Biochemistry, 32(37), 1993, pp. 9792-9797
A group of synthetic peptides having an amino acid sequence related to
the N-terminal region of the influenza virus hemagglutinin HA-2 chain
can induce phospholipid membrane fusion in a pH-dependent manner. The
se peptides bind to membranes to form alpha-helices even at pH's where
no fusion activity is seen. We determined the orientation of these al
pha-helical peptides in lipid multibilayers using attenuated total ref
lection infrared spectroscopy and found that the peptide alpha-helices
took a preferential orientation, the helix axis being about 70-degree
s from the normal of the membrane plane, or in other words rather para
llel to the membrane plane. The orientation was almost independent of
pH and a modification of the N-terminal amino group which reduced the
fusion activity of the peptides. The determination was carried out for
peptides in lipid multibilayers in dry or hydrated (membranes equilib
rated with D2O vapor) conditions. Although a slight decrease in the he
lix orientation angle from the membrane normal was noticed for a hydra
ted system, the difference between the results for dry and hydrated co
nditions was small.