Millar N S, Chambers P, Emmerson P T
Department of Biochemistry, University of Newcastle upon Tyne, U.K.
J Gen Virol. 1988 Mar;69 ( Pt 3):613-20. doi: 10.1099/0022-1317-69-3-613.
The nucleotide sequences of the fusion (F) and haemagglutinin-neuraminidase (HN) glycoprotein genes of the extremely avirulent Newcastle disease virus (NDV) strain Ulster have been determined by sequencing cDNA clones derived from viral genomic RNA. Open reading frames, assumed to encode the F0 and HN0 glycoprotein precursors, were 553 and 616 amino acids long, respectively. Comparisons of the two glycoprotein sequences with those of more virulent NDV strains suggested an explanation for the molecular basis of the wide-ranging differences in virulence observed between strains of NDV. The open reading frame corresponding to the Ulster HN glycoprotein extended beyond the C terminus of more virulent strains. This C-terminal extension was assumed to be responsible for the origin of the HN precursor (HN0) found in strain Ulster and other extremely avirulent strains of NDV. There were fewer basic amino acids at the cleavage site of F0 in strain Ulster than are present in more virulent strains, which may be responsible for the absence of cleavage and activation of F0 from this strain in many host cells. In more virulent strains of NDV, as well as in other paramyxoviruses, a phenylalanine residue occurs at the N terminus of the F1 cleavage fragment. The occurrence of a leucine residue at this position in strain Ulster may be partly responsible for the lack of virulence of this strain.
通过对源自病毒基因组RNA的cDNA克隆进行测序，已确定了极低毒力新城疫病毒（NDV）毒株阿尔斯特株的融合（F）糖蛋白基因和血凝素神经氨酸酶（HN）糖蛋白基因的核苷酸序列。推测编码F0和HN0糖蛋白前体的开放阅读框分别长553和616个氨基酸。将这两种糖蛋白序列与毒力更强的NDV毒株的序列进行比较，为NDV毒株间观察到的毒力广泛差异的分子基础提供了解释。与阿尔斯特株HN糖蛋白相对应的开放阅读框延伸至毒力更强毒株的C末端之外。这种C末端延伸被认为是阿尔斯特株和其他极低毒力NDV毒株中发现的HN前体（HN0）的起源原因。阿尔斯特株F0裂解位点的碱性氨基酸比毒力更强的毒株少，这可能是该毒株在许多宿主细胞中F0缺乏裂解和激活的原因。在毒力更强的NDV毒株以及其他副粘病毒中，F1裂解片段的N末端存在一个苯丙氨酸残基。阿尔斯特株在该位置出现亮氨酸残基可能是该毒株缺乏毒力的部分原因。
