Conformation and interaction with the membrane models of the amino-terminal peptide of influenza virus hemagglutinin HA2 at fusion pH

Conformations of a 48-mer peptide corresponding to the amino-terminal regio n of influenza HA2 in aqueous and membranous environments were studied. In aqueous solution the peptide was found to be oligomeric and its helicity wa s enhanced at higher concentrations. The conformation in phospholipid bilay er and insertion depth into the sodium dodecyl sulfate (SDS) micelle for th e fusion peptide were in line with those determined for the amino-terminal 25-mer analog. The turn of residues 28-31 found in the crystal structure of hemagglutinin at neutral pH persisted in the presence of SDS at pH 5.0. Ex cept for the turn, conformational lability of the amino portion of HA2 is s uggested by comparison of the secondary structure determined herein with th at obtained with the influenza fusion protein crystallized in the aqueous p hase at neutral pH. The backbone amide proton exchange experiment suggested an interaction with the micellar surface for the segment carboxy-terminal to the fusion peptide domain. (C) 2001 Elsevier Science.