Ghosh J K, Ovadia M, Shai Y
Department of Membrane Research and Biophysics, The Weizmann Institute of Science, Rehovot, 76100 Israel.
Biochemistry. 1997 Dec 9;36(49):15451-62. doi: 10.1021/bi971152i.
We have detected a leucine zipper-like motif in the ectodomain of the Sendai virus fusion protein (aa 269-307) which is extremely conserved in the family of Sendai viruses. To find a possible role for this motif, we synthesized SV-269, a 39 amino acid peptide corresponding to this domain, and a mutant peptide, MuSV-269, with an amino acid pair interchanged their positions. The peptides were labeled with fluorescent probes at their N-terminal amino acid and functionally and structurally characterized. The data show that SV-269, but not MuSV-269, specifically binds Sendai virus. Expectedly, SV-269 is more active than the mutant MuSV-269 in inhibiting Sendai virus-mediated hemolysis. Fluorescence studies reveal that SV-269 assembles in aqueous solution, binds to zwitterionic PC and negatively-charged PS/PC vesicles, and assembles therein. Although MuSV-269 similarly binds to both types of vesicles, it only slightly assembles in solution and not at all in membranes. Moreover, SV-269, but not MuSV-269, coassembles with the biologically-active heptad repeats SV-150 and SV-473 (Rapaport et al. , 1995) in solution as revealed by fluorescence and circular dichroism (CD) spectroscopy, and with SV-150 within negatively-charged PS/PC and zwitterionic PC vesicles. Despite these differences, both SV-269 and MuSV-269 adopt similar secondary structures in 40% TFE and 1% SDS as revealed by CD spectroscopy, and disrupt the packing of the lipid bilayers to the same extent, as shown by the dissipation of diffusion potential. The role of this leucine zipper motif is discussed in terms of the assembly of the Sendai virus fusion protein in solution and within membranes. Since most of the heptadic leucines are also conserved in the corresponding domains of other paramyxoviruses such as rinderpest, measles, SV5, and parainfluenza, it may indicate a similar role of this domain in these viruses as well.
我们在仙台病毒融合蛋白的胞外结构域（氨基酸269 - 307）中检测到一个类似亮氨酸拉链的基序，该基序在仙台病毒家族中极为保守。为了探究这个基序可能的作用，我们合成了SV - 269，一种对应于该结构域的39个氨基酸的肽段，以及一个突变肽段MuSV - 269，其中一对氨基酸互换了位置。这些肽段在其N端氨基酸处用荧光探针标记，并对其功能和结构进行了表征。数据表明，SV - 269能特异性结合仙台病毒，而MuSV - 269不能。不出所料，在抑制仙台病毒介导的溶血方面，SV - 269比突变体MuSV - 269更具活性。荧光研究表明，SV - 269在水溶液中组装，能结合两性离子PC以及带负电荷的PS/PC囊泡，并在其中组装。虽然MuSV - 269同样能结合这两种类型的囊泡，但它在溶液中只是轻微组装，在膜中则完全不组装。此外，如荧光和圆二色性（CD）光谱所示，SV - 269能与具有生物活性的七肽重复序列SV - 150和SV - 473（Rapaport等人，1995）在溶液中共组装，并且能与带负电荷的PS/PC和两性离子PC囊泡中的SV - 150共组装，而MuSV - 269则不能。尽管存在这些差异，但如CD光谱所示，在40%的TFE和1%的SDS中，SV - 269和MuSV - 269都具有相似的二级结构，并且如扩散电位的消散所示，它们对脂质双层堆积的破坏程度相同。本文从仙台病毒融合蛋白在溶液和膜中的组装方面讨论了这个亮氨酸拉链基序的作用。由于大多数七肽亮氨酸在其他副粘病毒（如牛瘟病毒、麻疹病毒、SV5和副流感病毒）的相应结构域中也保守，这可能表明该结构域在这些病毒中也具有类似的作用。
