Roles of the highly conserved amino acids in the second receptor binding site of the Newcastle disease virus HN protein

Yaqing Liu,Miaomiao Chi,Hongling Wen,Li Zhao,Yanyan Song,Na Liu,Ying Liu,Zhiyu Wang

doi:10.1186/s12985-019-1273-y

Yaqing Liu, Miaomiao Chi + Show 6 more

Open Access

https://doi.org/10.1186/s12985-019-1273-y

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Journal: Virology journal	Publication Date: Dec 1, 2019
Citations: 7	License type: open-access

Affiliation: Shandong University

Abstract

BackgroundThe paramyxovirus haemagglutinin-neuraminidase (HN) is a multifunctional protein that is responsible for attachment to receptors, removal of receptors from infected cells to prevent viral self-aggregation (neuraminidase, NA) and fusion promotion. It is commonly accepted that there are two receptor binding sites in the globular head of HN, and the second receptor binding site is only involved in the function of receptor binding and fusion promotion.Methods10 conserved residues in the second receptor binding site of Newcastle disease virus (NDV) HN were chosen and substituted to alanine (A). The desired mutants were examined to detect the functional change in hemadsorption (HAD) ability, NA activity and fusion promotion ability.ResultsThe HAD and fusion promotion ability of mutants C172A, R174A, C196A, D198A, Y526A and E547A were abolished. Compared with wild-type (wt) HN, the HAD of mutants T167A, S202A and R516A decreased to 55.81, 44.53, 69.02%, respectively, and the fusion promotion ability of these three mutants decreased to 54.74, 49.46, 65.26%, respectively; however, mutant G171A still maintained fusion promotion ability comparable with wt HN but had impaired HAD ability. All the site-directed mutations altered the NA activity of NDV HN without affecting protein cell surface expression.ConclusionsThe data suggest that mutants C172A, R174A, C196A, D198A, Y526A and E547A do not allow the conformational change that is required for fusion promotion ability and HAD activity, while the other mutants only affect the conformational change to a limited extent, except mutant G171A with intact fusion promotion ability. Overall, the conserved amino acids in the second receptor binding site, especially residues C172, R174, C196, D198, Y526 and E547, are crucial to normal NDV HN protein function.

Highlights

The paramyxovirus haemagglutinin-neuraminidase (HN) is a multifunctional protein that is responsible for attachment to receptors, removal of receptors from infected cells to prevent viral self-aggregation and fusion promotion
In addition to these sitedirected mutants, 8 fragment deletion or replacement mutants corresponding to the four loops of the second receptor binding site of Newcastle disease virus (NDV) HN were constructed named Ch1, Ch2, Ch3, Ch4, De1, De2, De3 and De4
The ectodomain of paramyxovirus attachment proteins, including the NDV HN, consists of a long stalk that mediates the interaction with the homologous F, and the stalk is connected to the terminal globular domain that has receptor binding ability and NA activity [22]

Summary

Introduction

The paramyxovirus haemagglutinin-neuraminidase (HN) is a multifunctional protein that is responsible for attachment to receptors, removal of receptors from infected cells to prevent viral self-aggregation (neuraminidase, NA) and fusion promotion. NDV, named avian paramyxovirus type 1 (APMV-1), is an enveloped, non-segmented, To process infection, the lipid envelope of NDV must fuse with the membrane of the host cell and cause the formation of syncytia. The phenomenon of membrane fusion is a receptor-dependent, pH-independent process that requires the cooperation of two glycoproteins embedded in the lipid membrane, F and HN proteins [6]. Regarding the mechanism of how HN cooperates with F, there are some different opinions: first, the protein-protein interactions. Regardless of the mechanism, it is undeniable that the HN protein plays an important role in activating the F protein to achieve membrane fusion

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