id	author	title	date	pages	extension	mime	words	sentences	flesch	summary	cache	txt
cord-333525-67bbmo4m	Yao, Qianqian	Negatively charged residues in the endodomain are critical for specific assembly of spike protein into murine coronavirus	2013-07-01		.txt	text/plain	5251	238	53	In the current study, we analyzed the effects of the Endo charge-rich motif on virion incorporation of MHV S protein through substitutions of the homologous regions from the alphacoronavirus porcine transmissible gastroenteritis virus (TGEV), the betacoronaviruses bovine coronavirus (BCoV) and SARS-CoV, or the gammacoronavirus avian infectious bronchitis virus (IBV). Although the S2 portions of coronavirus S proteins show some degree of conservation, the Tm and Endo domains are highly divergent, with the exception of a conserved cluster of seven hydrophobic residues (WPWYVWL) at the start of Tm. To evaluate the functionality of different C-terminal sequence motifs in the MHV S protein, we constructed two sets of mutants in which the ectodomain of either S protein or HK protein was fused to the Tm and Endo domains from TGEV (an alphacoronavirus), BCoV (a betacoronavirus), SARS-CoV (a betacoronavirus), or IBV (a gammacoronavirus) ( Fig. 2A) . Reverting mutations in TGEV chimeras improved S assembly by eliminating positively charged residues in the endodomain MHV S protein mutants containing the entire carboxy terminus or just the charge-rich motif of TGEV S (Mut-TGEV and Mut-MMT) produced irregular plaques (Figs.	./cache/cord-333525-67bbmo4m.txt	./txt/cord-333525-67bbmo4m.txt