title: 'a'-Position-mutated and G4-mutated hemagglutinin-neuraminidase proteins of Newcastle disease virus impair fusion and hemagglutinin-neuraminidase-fusion interaction by different mechanisms.
abstract: OBJECTIVE
  To determine the effects of heptad repeat regions (HRs) and N-linked carbohydrate sites of the Newcastle disease virus hemagglutinin-neuraminidase (HN) protein on fusion of HN and fusion (F) proteins and HN-F interaction.
  
  
  METHODS
  We mutated six 'a' residues in the HRs and four asparagines in N-linked carbohydrate sites to alanine in the HN protein. A vaccinia-T7 RNA polymerase expression system was used to express HN cDNAs in BHK-21 cells to determine the HN functions. Deglycosylation was treated with PGNase F digestion. The formation of HN-F protein complexes was determined by the coimmunoprecipitation assay.
  
  
  RESULTS
  Each HR-mutated protein interfered with fusion and the HN-F interaction. The G4-mutated protein not only impaired fusion and HN-F interaction but also decreased activities in cell fusion promotion, hemadsorption and neuraminidase.
  
  
  CONCLUSIONS
  It is assumed that two different mechanisms for mutations in these two regions are responsible for the decreased fusion promotion activity and the reduced ability of interaction with F protein. Mutations in the HRs impair fusion and HN-F interaction by altering the transmission of a signal from the globular domain to the F-specific region in the stalk, but the G4 mutation modulates fusion and HN-F interaction by the misfolding of some important structures.
authors.affiliation: Department of Virology, School of Public Health, Shandong University, Jinan 250012, China.
authors.forename: Fu-lu
authors.initials: FL
authors.lastname: Chu
authors.forename: Hong-ling
authors.initials: HL
authors.lastname: Wen
authors.forename: Wen-qiang
authors.initials: WQ
authors.lastname: Zhang
authors.forename: Bin
authors.initials: B
authors.lastname: Lin
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Cheng-xi
authors.initials: CX
authors.lastname: Sun
authors.forename: Gui-jie
authors.initials: GJ
authors.lastname: Ren
authors.forename: Yan-yan
authors.initials: YY
authors.lastname: Song
authors.forename: Zhiyu
authors.initials: Z
authors.lastname: Wang
mesh_terms: D000818:Animals; D002460:Cell Line; D006224:Cricetinae; D004926:Escherichia coli / Q000235:genetics; D015707:HN Protein / Q000737:chemistry / Q000235:genetics* / Q000502:physiology; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009522:Newcastle disease virus / Q000201:enzymology / Q000235:genetics* / Q000502:physiology; D017434:Protein Structure, Tertiary; D014760:Viral Fusion Proteins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology; D053586:Virus Internalization
chemical_list: D015707:HN Protein; D014760:Viral Fusion Proteins