id	author	title	date	pages	extension	mime	words	sentences	flesch	summary	cache	txt
cord-273891-7w334xgt	Kirchdoerfer, Robert N.	Receptor binding and proteolysis do not induce large conformational changes in the SARS-CoV spike	2018-03-31		.txt	text/plain	3300	170	55	The viral spike glycoprotein (S) utilizes angiotensin-converting enzyme 2 (ACE2) as a host protein receptor and mediates fusion of the viral and host membranes, making S essential to viral entry into host cells and host species tropism. Subsequent studies of the highly pathogenic human coronavirus S proteins of SARS-64 CoV 15,22 and MERS-CoV 17,22 showed that these viral S1 RBD do indeed sample an 'up' 65 conformation where the receptor-binding site is accessible. 70 To examine the hypothesized conformational transitions induced by proteolysis and 71 receptor binding, we used single-particle cryo-EM to determine structures of S in uncleaved, 72 S1/S2 cleaved and ACE2-bound states. Three-dimensional classification of the S1 RBD 73 positions and corresponding atomic protein models revealed that neither ACE2-binding nor 74 trypsin cleavage at the S1/S2 boundary induced substantial conformational changes in the CoV may use a distinct mechanism of FP2 membrane insertion. Cryo-electron microscopy structures of the SARS-CoV spike glycoprotein 381 reveal a prerequisite conformational state for receptor binding	./cache/cord-273891-7w334xgt.txt	./txt/cord-273891-7w334xgt.txt