id	author	title	date	pages	extension	mime	words	sentences	flesch	summary	cache	txt
cord-352511-gkm7i62s	Yamada, Yoshiyuki	Acquisition of Cell–Cell Fusion Activity by Amino Acid Substitutions in Spike Protein Determines the Infectivity of a Coronavirus in Cultured Cells	2009-07-02		.txt	text/plain	5731	317	55	title: Acquisition of Cell–Cell Fusion Activity by Amino Acid Substitutions in Spike Protein Determines the Infectivity of a Coronavirus in Cultured Cells Here we report that acquisition of the cell–cell fusion activity by amino acid mutations in the S protein determines the infectivity of IBV in cultured cells. This study demonstrates that acquisition of the cell–cell fusion activity in S protein determines the selection and/or adaptation of a coronavirus from chicken embryo to cultured cells of human and animal origins. In this study, we report that acquisition of the cell-cell fusion activity by point mutations in the spike (S) protein of avian coronavirus infectious bronchitis virus (IBV) plays a critical role in adaptation and/or selection of a variant that infects cultured cells. Sequence comparison of two S protein constructs, S(EP3) and S(CK), cloned from EP3 and CK-adapted IBV strains, respectively, showed amino acid substitutions at 31 positions (Fig. 1a) .	./cache/cord-352511-gkm7i62s.txt	./txt/cord-352511-gkm7i62s.txt