Hydrophobic binding of the ectodomain of influenza hemagglutinin to membranes occurs through the "fusion peptide".
Toward elucidating molecular details of virus-induced membrane fusion, we have studied the low pH-triggered interaction of the bromelain-solubilized ectodomain of influenza hemagglutinin with liposomes. Polypeptide segments which insert into the apolar phase of the lipid bilayer were first labeled specifically using either of the two membrane-restricted carbene-generating reagents, 3-(trifluoromethyl)-3-([125I]iodophenyl)diazirine and 1-palmitoyl-2-[11-[4-[3-(trifluoromethyl)diazirinyl]phenyl] undecanoyl]-sn-glycero-3-phosphorylcholine, and were then identified on the basis of cyanogen bromide and 2-(2-nitrophenylsulfenyl)-3-methyl-3'-bromoindolenine-skatole fragment analysis and Edman degradations. Here, we demonstrate that the hydrophobic interaction is mediated solely by the so-called "fusion peptide" which corresponds to the NH2-terminal segment of the BHA2 subunit of nature influenza hemagglutinin. Predominant sites of labeling within that segment were Phe-3, Ile-6, Phe-9, Trp-14, Met-17, and Trp-21. The average 3-4 residue spacing between consecutive labeled amino acid side chains suggests a helical structure of that segment with an amphiphilic character.
Harter
C
C
Department of Biochemistry, Swiss Federal Institute of Technology, Zürich.
James
P
P
Bächi
T
T
Semenza
G
G
Brunner
J
J
D001963:Bromelains; D006389:Hemagglutinins, Viral / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D009980:Influenza A virus / Q000648:ultrastructure*; D008561:Membrane Fusion; D010446:Peptide Fragments / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D012995:Solubility; D014760:Viral Fusion Proteins / Q000378:metabolism*
D006389:Hemagglutinins, Viral; D010446:Peptide Fragments; D014760:Viral Fusion Proteins; D001963:Bromelains