id	author	title	date	pages	extension	mime	words	sentences	flesch	summary	cache	txt
cord-291306-g9qmmugg	Vey, Martin	Hemagglutinin activation of pathogenic avian influenza viruses of serotype H7 requires the protease recognition motif R-X-K/R-R	1992-05-31		.txt	text/plain	2436	131	54	It has long been known that the hemagglutinins activated by these enzymes have multiple lysine and arginine residues at theircleavage sites, and it has been shown that most of these basic amino acids are critical for cleavage activation (7). Comparison of the published hemagglutinin sequences of the pathogenic avian influenza-A-viruses of serotype H7 reveals a number of conserved amino acids upstream of the cleavage site, notably a series of arginine and lysine residues in positions -1 to -6 and two proline residues in positions -7 or -8 and in position -10 (Table 1) . To determine whether these conserved regions are important for the cleavability of the H7 hemagglutinin, we subjected a cDNA clone of the hemagglutinin of influenza virus AIFPV/Rostock/34 to site-directed mutagenesis at the cleavage site and from the panel of mutants obtained, we have selected two groups. In previous work, pathogenic variants with increased hemagglutinin cleavability could be obtained, when apathogenic avian influenza virus strains were adapted to non-permissive host cells (11, 9, 16) .	./cache/cord-291306-g9qmmugg.txt	./txt/cord-291306-g9qmmugg.txt