Acquisition of a novel eleven amino acid insertion directly N-terminal to a tetrabasic cleavage site confers intracellular cleavage of an H7N7 influenza virus hemagglutinin.
A critical feature of highly pathogenic avian influenza viruses (H5N1 and H7N7) is the efficient intracellular cleavage of the hemagglutinin (HA) protein. H7N7 viruses also exist in equine species, and a unique feature of the equine H7N7 HA is the presence of an eleven amino acid insertion directly N-terminal to a tetrabasic cleavage site. Here, we show that three histidine residues within the unique insertion of the equine H7N7 HA are essential for intracellular cleavage. An asparagine residue within the insertion-derived glycosylation site was also found to be essential for intracellular cleavage. The presence of the histidine residues also appear to be involved in triggering fusion, since mutation of the histidine residues resulted in a destabilizing effect. Importantly, the addition of a tetrabasic site and the eleven amino acid insertion conferred efficient intracellular cleavage to the HA of an H7N3 low pathogenicity avian influenza virus. Our studies show that acquisition of the eleven amino acid insertion offers an alternative mechanism for intracellular cleavage of influenza HA.
Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
Brian S
BS
Hamilton
Xiangjie
X
Sun
Changik
C
Chung
Gary R
GR
Whittaker
D000595:Amino Acid Sequence; D000818:Animals; D002522:Chlorocebus aethiops; D004252:DNA Mutational Analysis; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics* / Q000378:metabolism; D006868:Hydrolysis; D053126:Influenza A Virus, H7N7 Subtype / Q000235:genetics* / Q000502:physiology; D016254:Mutagenesis, Insertional; D014709:Vero Cells; D014760:Viral Fusion Proteins / Q000235:genetics* / Q000378:metabolism; D053586:Virus Internalization
D019267:Hemagglutinin Glycoproteins, Influenza Virus; D014760:Viral Fusion Proteins