N- and C-terminal residues combine in the fusion-pH influenza hemagglutinin HA(2) subunit to form an N cap that terminates the triple-stranded coiled coil.Chen, J., Skehel, J.J., Wiley, D.C.
(1999) Proc Natl Acad Sci U S A 96: 8967-8972
- PubMed: 10430879
- DOI: https://doi.org/10.1073/pnas.96.16.8967
- Primary Citation of Related Structures:
- PubMed Abstract:
The structure of a stable recombinant ectodomain of influenza hemagglutinin HA(2) subunit, EHA(2) (23-185), defined by proteolysis studies of the intact bacterial-expressed ectodomain, was determined to 1.9-A resolution by using x-ray crystallography. The structure reveals a domain composed of N- and C-terminal residues that form an N cap terminating both the N-terminal alpha-helix and the central coiled coil. The N cap is formed by a conserved sequence, and part of it is found in the neutral pH conformation of HA. The C-terminal 23 residues of the ectodomain form a 72-A long nonhelical structure ordered to within 7 residues of the transmembrane anchor. The structure implies that continuous alpha helices are not required for membrane fusion at either the N or C termini. The difference in stability between recombinant molecules with and without the N cap sequences suggests that additional free energy for membrane fusion may become available after the formation of the central triple-stranded coiled coil and insertion of the fusion peptide into the target membrane.
Department of Cellular and Molecular Biology, Howard Hughes Medical Institute, Harvard University, 7 Divinity Avenue, Cambridge, MA 02138, USA.