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Crystal structure of rat coronavirus strain New-Jersey Hemagglutinin-Esterase in complex with 4N-acetyl sialic acid
Structural highlights
FunctionQ3HS77_9BETC May serve as a secondary viral attachment protein for initiating infection, the spike protein being the major one. Structural protein that makes short spikes at the surface of the virus. Contains receptor binding and receptor-destroying activities. Seems to be a 'luxury' protein that is not absolutely necessary for virus infection in culture.[RuleBase:RU361278] Publication Abstract from PubMedHemagglutinin-esterases (HEs) are bimodular envelope proteins of orthomyxoviruses, toroviruses, and coronaviruses with a carbohydrate-binding "lectin" domain appended to a receptor-destroying sialate-O-acetylesterase ("esterase"). In concert, these domains facilitate dynamic virion attachment to cell-surface sialoglycans. Most HEs (type I) target 9-O-acetylated sialic acids (9-O-Ac-Sias), but one group of coronaviruses switched to using 4-O-Ac-Sias instead (type II). This specificity shift required quasisynchronous adaptations in the Sia-binding sites of both lectin and esterase domains. Previously, a partially disordered crystal structure of a type II HE revealed how the shift in lectin ligand specificity was achieved. How the switch in esterase substrate specificity was realized remained unresolved, however. Here, we present a complete structure of a type II HE with a receptor analog in the catalytic site and identify the mutations underlying the 9-O- to 4-O-Ac-Sia substrate switch. We show that (i) common principles pertaining to the stereochemistry of protein-carbohydrate interactions were at the core of the transition in lectin ligand and esterase substrate specificity; (ii) in consequence, the switch in O-Ac-Sia specificity could be readily accomplished via convergent intramolecular coevolution with only modest architectural changes in lectin and esterase domains; and (iii) a single, inconspicuous Ala-to-Ser substitution in the catalytic site was key to the emergence of the type II HEs. Our findings provide fundamental insights into how proteins "see" sugars and how this affects protein and virus evolution. Coronavirus receptor switch explained from the stereochemistry of protein-carbohydrate interactions and a single mutation.,Bakkers MJ, Zeng Q, Feitsma LJ, Hulswit RJ, Li Z, Westerbeke A, van Kuppeveld FJ, Boons GJ, Langereis MA, Huizinga EG, de Groot RJ Proc Natl Acad Sci U S A. 2016 May 16. pii: 201519881. PMID:27185912[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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