Tong N, Nakajima K, Nakajima S
Department of Microbiology, Institute of Public Health, Tokyo, Japan.
Microbiol Immunol. 1995;39(9):687-92. doi: 10.1111/j.1348-0421.1995.tb03257.x.
A temperature-sensitive (ts) mutant of the influenza virus A/WSN/33 strain, ts-134, possessed a defect in intracellular transport at the nonpermissive temperature and marked thermolability of hemagglutinin (HA) activity at 51 C. These were caused by a change at amino acid residue 157 from tyrosine to histidine in the HA protein. We isolated 37 spontaneous revertant clones from ts-134 at the nonpermissive temperature and determined their HA sequences. The deduced amino acid sequences demonstrated that one was a true revertant and the others were revertants with suppressor mutations, each of which had an additional amino acid change besides those of ts-134. The changed amino acids were located at 14 positions on the HA molecule, and eight of them were found in multiple revertants. These were located in five to six distinct regions on the three-dimensional structure of the HA molecule. However, the heat stability of HAs in the revertants was recovered differently depending on the sites of the changed amino acids. The kinetics of transport of the HA protein in the revertants were slightly delayed compared to the wild-type both at permissive and nonpermissive temperatures.
甲型流感病毒A/WSN/33株的温度敏感（ts）突变体ts-134在非允许温度下细胞内运输存在缺陷，且在51℃时血凝素（HA）活性具有明显的热不稳定性。这些是由HA蛋白中第157位氨基酸残基从酪氨酸变为组氨酸所致。我们在非允许温度下从ts-134中分离出37个自发回复突变克隆，并确定了它们的HA序列。推导的氨基酸序列表明，一个是真正的回复突变体，其他是带有抑制突变的回复突变体，每个除了ts-134的那些变化外还有一个额外的氨基酸变化。变化的氨基酸位于HA分子的14个位置，其中8个在多个回复突变体中出现。它们位于HA分子三维结构的五到六个不同区域。然而，回复突变体中HA的热稳定性根据变化氨基酸的位点不同而有所恢复。与野生型相比，回复突变体中HA蛋白在允许温度和非允许温度下的运输动力学都略有延迟。
