id	author	title	date	pages	extension	mime	words	sentences	flesch	summary	cache	txt
cord-295482-qffg6r91	Wong, Alan H. M.	Receptor-binding loops in alphacoronavirus adaptation and evolution	2017-11-23		.txt	text/plain	6609	373	51	Here we report the X-ray crystal structure of the receptor-binding domain (RBD) of the human coronavirus, HCoV-229E, in complex with the ectodomain of its receptor, aminopeptidase N (APN). Phylogenetic analysis shows that the natural HCoV-229E receptor-binding loop variation observed defines six RBD classes whose viruses have successively replaced each other in the human population over the past 50 years. The structure shows that receptor binding is mediated solely by three extended loops, a feature shared by HCoV-NL63 and the closely related porcine respiratory coronavirus, PRCoV. The six RBDs differ in their receptor-binding affinity and their ability to be bound by a neutralizing antibody (9.8E12) and taken together, our findings suggest that the HCoV-229E sequence variation observed arose through adaptation and selection. HCoV-229E infection in humans does not provide protection against different isolates 37 , and viruses that contain a new RBD class that cannot be bound by the existing repertoire of loop-binding neutralizing antibodies provide an explanation for this observation.	./cache/cord-295482-qffg6r91.txt	./txt/cord-295482-qffg6r91.txt