Iorio R M, Field G M, Sauvron J M, Mirza A M, Deng R, Mahon P J, Langedijk J P
Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, Worcester, Massachusetts 01655-0122, USA.
J Virol. 2001 Feb;75(4):1918-27. doi: 10.1128/JVI.75.4.1918-1927.2001.
The terminal globular domain of the paramyxovirus hemagglutinin-neuraminidase (HN) glycoprotein spike has a number of conserved residues that are predicted to form its neuraminidase (NA) active site, by analogy to the influenza virus neuraminidase protein. We have performed a site-directed mutational analysis of the role of these residues in the functional activity of the Newcastle disease virus (NDV) HN protein. Substitutions for several of these residues result in a protein lacking both detectable NA and receptor recognition activity. Contribution of NA activity, either exogenously or by coexpression with another HN protein, partially rescues the receptor recognition activity of these proteins, indicating that the receptor recognition deficiencies of the mutated HN proteins result from their lack of detectable NA activity. In addition to providing support for the homology-based predictions for the structure of HN, these findings argue that (i) the HN residues that mediate its NA activity are not critical to its attachment function and (ii) NA activity is required for the protein to mediate binding to receptors.
副粘病毒血凝素神经氨酸酶（HN）糖蛋白刺突的末端球状结构域有许多保守残基，通过与流感病毒神经氨酸酶蛋白类比，预计这些残基会形成其神经氨酸酶（NA）活性位点。我们对这些残基在新城疫病毒（NDV）HN蛋白功能活性中的作用进行了定点突变分析。这些残基中的几个被取代后，产生的蛋白既缺乏可检测到的NA活性，也缺乏受体识别活性。外源性地或通过与另一种HN蛋白共表达来提供NA活性，可部分挽救这些蛋白的受体识别活性，这表明突变的HN蛋白的受体识别缺陷是由于它们缺乏可检测到的NA活性。除了为基于同源性的HN结构预测提供支持外，这些发现还表明：（i）介导其NA活性的HN残基对其附着功能并不关键；（ii）该蛋白介导与受体结合需要NA活性。
