Identification of defects in the neuraminidase gene of four temperature-sensitive mutants of A/WSN/33 influenza virus |
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| Authors: | T J Bos D P Nayak |
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| Affiliation: | 1. Joint International Research Laboratory of Agriculture and Agri-Product Safety, The Ministry of Education of China, Yangzhou University, Yangzhou, 225009, China;2. Animal Infectious Disease Laboratory, College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, China;3. Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, 225009, China;4. Jiangsu Key Laboratory of Zoonosis, Yangzhou, 225009, China;5. Institute of Translational Medicine, Key Laboratory of Geriatric Disease Prevention and Control of Jiangsu Province, Medical College, Yangzhou University, Yangzhou, 225009, China;1. Animal Disease Investigation and Control Division (ADICD), Department of Livestock Services (DLS), Hariharbhawan, Lalitpur 44600, Nepal;2. Central Referral Veterinary Hospital, Department of Livestock Services (DLS), Tripureshwar, Kathmandu, Nepal;1. School of Life Sciences, Central University of Gujarat, Gandhinagar, 382030, Gujarat, India;2. Department of Biology, Indian Institute of Sciences Education and Research (IISER), Bhopal, 462 066, Madhya Pradesh, India;3. Biology Division, Indian Institute of Sciences Education and Research (IISER), Pune, 411008, Maharashtra, India |
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| Abstract: | Four influenza (A/WSN/33) mutants, temperature sensitive (ts) for neuraminidase (NA) (Sugiura et al., 1972, 1975) were analyzed. All four ts mutants were found to be defective at the nonpermissive temperature (39.5 degrees) both in enzymatic activity and in transport to the cell surface. Upon shift down to the permissive temperature (33 degrees), enzymatic activity and transport to the cell surface were both restored suggesting that the mutational defect is reversible. Comparative sequence analysis of the NA gene from ts mutants, their revertants and wild type WSN viruses revealed that in each case single point mutations causing amino acid substitutions were associated with the ts defect. The positions of each point mutation when mapped in the three-dimensional structure of NA varied. However, all four amino acid substitutions were located in beta-sheet strands of the head region. Several other amino acid changes not essential for the ts phenotype were found in each mutant NA. The nonessential changes were localized either in the stalk region or in the loop structures of the head, but none in the beta-sheet strands. Because both enzymatic activity and transport of NA were affected in all four mutants, we propose that the mutational phenotype is caused by a change in overall conformation rather than a localized change in the sialic acid binding site. |
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