id	author	title	date	pages	extension	mime	words	sentences	flesch	summary	cache	txt
cord-266585-jfjrk9gy	Fang, Shouguo	An arginine-to-proline mutation in a domain with undefined functions within the helicase protein (Nsp13) is lethal to the coronavirus infectious bronchitis virus in cultured cells	2007-02-05		.txt	text/plain	7152	356	56	During construction of an infectious clone from a Vero cell-adapted coronavirus infectious bronchitis virus (IBV), we found that a G–C point mutation at nucleotide position 15526, causing Arg-to-Pro mutation at amino acid position 132 of the helicase protein, is lethal to the infectivity of IBV on Vero cells. Further characterization of the in vitro-synthesized full-length transcripts containing the G15526C mutation demonstrated that this mutation blocks the transcription of subgenomic RNAs. Substitution mutation of the Arg132 residue to a positively charged amino acid (Lys) affected neither the infectivity of the in vitro-synthesized transcripts nor the growth properties of the rescued virus. To further demonstrate that the failure to rescue infectious virus from the G15526C mutant transcripts is due to a defect in subgenomic RNA transcription, the full-length clones with and without the G15526C mutation were used to generate recombinant IBV expressing the enhanced green fluorescent protein (EGFP) by replacing the 5a gene with EGFP.	./cache/cord-266585-jfjrk9gy.txt	./txt/cord-266585-jfjrk9gy.txt