title: Mutations of two transmembrane cysteines of hemagglutinin (HA) from influenza A H3N2 virus affect HA thermal stability and fusion activity.
abstract: Influenza A H3N2 virus caused 1968 Hong Kong influenza pandemic, and has since been one of the most prevalent seasonal influenza viruses in global populations, representing a credible pandemic candidate in future. Previous studies have established that the hemagglutinin (HA) protein is the predominant antigen and executes receptor binding and membrane fusion. Homologous sequence analysis of all HA subtypes of influenza viruses revealed that two cysteine residues (540 and 544) are uniquely present in the transmembrane domain (TM) of HA proteins from all influenza A H3N2 viruses. However, the functions of these two cysteines have not been fully studied. Here, we generated three mutants (C540S, C544L, and 2C/SL) to investigate the effects of the two TM cysteines on the biological functions of H3 HA. We herein presented evidences that the mutations of one or two of the cysteines did not affect the proper expressions of HA proteins in cells, and more importantly all mutant H3 HAs showed decreased thermal stability but increased fusion activity in comparison with wildtype HA. Our results taken together demonstrated that the two TM cysteines are important for the biological functions of H3 HA proteins.
authors.affiliation: State Key Laboratory of Biocontrol, Life Sciences School, Sun Yat-sen University, Guangzhou 510006, People's Republic of China.
authors.forename: Shun
authors.initials: S
authors.lastname: Xu
authors.forename: Jianqiang
authors.initials: J
authors.lastname: Zhou
authors.forename: Kang
authors.initials: K
authors.lastname: Liu
authors.forename: Qiliang
authors.initials: Q
authors.lastname: Liu
authors.forename: Chunyi
authors.initials: C
authors.lastname: Xue
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Li
authors.forename: Jing
authors.initials: J
authors.lastname: Zheng
authors.forename: Dongyu
authors.initials: D
authors.lastname: Luo
authors.forename: Yongchang
authors.initials: Y
authors.lastname: Cao
mesh_terms: D002460:Cell Line; D003545:Cysteine / Q000235:genetics* / Q000378:metabolism; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D006358:Hot Temperature; D006801:Humans; D053122:Influenza A Virus, H3N2 Subtype / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007251:Influenza, Human / Q000821:virology*; D020125:Mutation, Missense; D055550:Protein Stability; D017434:Protein Structure, Tertiary
chemical_list: D019267:Hemagglutinin Glycoproteins, Influenza Virus; D003545:Cysteine