Webster R G, Air G M, Metzger D W, Colman P M, Varghese J N, Baker A T, Laver W G
J Virol. 1987 Sep;61(9):2910-6. doi: 10.1128/JVI.61.9.2910-2916.1987.
We previously determined, by X-ray crystallography, the three-dimensional structure of a complex between influenza virus N9 neuraminidase (NA) and the Fab fragments of monoclonal antibody NC-41 [P. M. Colman, W. G. Laver, J. N. Varghese, A. T. Baker, P. A. Tulloch, G. M. Air, and R. G. Webster, Nature (London) 326:358-363, 1987]. This antibody binds to an epitope on the upper surface of the NA which is made up of four polypeptide loops over an area of approximately 600 A2 (60 nm2). We now describe properties of NC-41 and other monoclonal antibodies to N9 NA and the properties of variants selected with these antibodies (escape mutants). All except one of the escape mutants had single amino acid sequence changes which affected the binding of NC-41 and which therefore are located within the NC-41 epitope. The other one had a change outside the epitope which did not affect the binding of any of the other antibodies. All the antibodies which selected variants inhibited enzyme activity with fetuin (molecular weight, 50,000) as the substrate, but only five, including NC-41, also inhibited enzyme activity with the small substrate N-acetylneuramin-lactose (molecular weight, 600). These five probably inhibited enzyme activity by distorting the catalytic site of the NA. Isolated, intact N9 NA molecules form rosettes in the absence of detergent, and these possess high levels of hemagglutinin activity (W.G. Laver, P.M. Colman, R.G. Webster, V.S. Hinshaw, and G.M. Air, Virology 137:314-323, 1984). The enzyme activity of N9 NA was inhibited efficiently by 2-deoxy-2,3-dehydro-N-acetylneuraminic acid, whereas hemagglutinin activity was unaffected. The NAs of several variants with sequence changes in the NC-41 epitope lost hemagglutinin activity without any loss of enzyme activity, suggesting that the two activities are associated with separate sites on the N9 NA head.
我们之前通过X射线晶体学确定了流感病毒N9神经氨酸酶（NA）与单克隆抗体NC-41的Fab片段形成的复合物的三维结构[P.M.科尔曼、W.G.拉弗、J.N.瓦尔盖斯、A.T.贝克、P.A.图洛克、G.M.艾尔和R.G.韦伯斯特，《自然》（伦敦）326:358 - 363，1987年]。该抗体结合到NA上表面的一个表位，该表位由四个多肽环组成，覆盖面积约为600 Ų（60 nm²）。我们现在描述NC-41和其他针对N9 NA的单克隆抗体的特性以及用这些抗体筛选出的变体（逃逸突变体）的特性。除了一个逃逸突变体外，其他所有突变体都有单个氨基酸序列变化，这些变化影响了NC-41的结合，因此位于NC-41表位内。另一个突变体在表位外有一个变化，不影响任何其他抗体的结合。所有筛选出变体的抗体都以胎球蛋白（分子量50,000）为底物抑制酶活性，但只有包括NC-41在内的五种抗体也以小底物N-乙酰神经氨酸乳糖（分子量600）抑制酶活性。这五种抗体可能通过扭曲NA的催化位点来抑制酶活性。在没有去污剂的情况下，分离的完整N9 NA分子形成玫瑰花结，并且这些分子具有高水平的血凝素活性（W.G.拉弗、P.M.科尔曼、R.G.韦伯斯特、V.S.欣肖和G.M.艾尔，《病毒学》137:314 - 323，1984年）。N9 NA的酶活性被2-脱氧-2,3-脱氢-N-乙酰神经氨酸有效抑制，而血凝素活性不受影响。在NC-41表位有序列变化的几个变体的NA失去了血凝素活性，而酶活性没有任何损失，这表明这两种活性与N9 NA头部的不同位点相关。
