THE RELATIONSHIP OF CONFORMATIONAL-CHANGES IN THE SENDAI VIRUS NUCLEOCAPSID TO PROTEOLYTIC CLEAVAGE OF THE NP POLYPEPTIDE
THE RELATIONSHIP OF CONFORMATIONAL-CHANGES IN THE SENDAI VIRUS NUCLEOCAPSID TO PROTEOLYTIC CLEAVAGE OF THE NP POLYPEPTIDE
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DOI：
10.1016/0042-6822(81)90235-x
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发表时间：
1981-01-01
期刊：
影响因子：
3.7
通讯作者：
CHOPPIN, PW
中科院分区：
文献类型：
--
作者：
HEGGENESS, MH;SCHEID, A;CHOPPIN, PW
先前的研究表明，副粘病毒核衣壳的构象在螺旋的柔性和卷曲方面变化很大，这种类型的变化对病毒装配和病毒RNA的转录可能是重要的。螺旋紧密盘绕并且在高盐浓度下相对不灵活（例如，1.0 M NaCl）并在低盐缓冲液（0.01 M）中松散卷曲或延伸。现已发现，盐诱导的构象变化可改变仙台病毒核衣壳蛋白（NP，MW. 60，000）至胰蛋白酶裂解。当核衣壳紧密卷曲时，NP被切割以产生单个主要切割产物（t48，MW约为0.0001）。48，000），其包含分子的原始N-末端。当核衣壳处于解螺旋状态时，t48进一步裂解为主要的N-末端产物t34和第二产物t15; t15可以进一步裂解产生t12。与. apprx不同。当NP裂解为t48时，12，000道尔顿的NP降解为小肽并从核衣壳中丢失，t34和t15（或t12）仍然与核衣壳结构结合，尽管它们彼此没有二硫键。仙台病毒的核衣壳含有t34和t15（或t12）具有相同的形态外观和响应可逆的盐浓度的变化，如由天然NP或t48组成的核衣壳。NP亚基的性质对决定核衣壳的螺旋构象很重要，因此存在于分子的N-末端48，000道尔顿处，不受进一步裂解的影响。与NP上胰蛋白酶裂解位点的构象依赖性暴露相反，核衣壳中的病毒RNA无法被RNase消化，而不管NP的构象或胰蛋白酶裂解状态的盐依赖性变化。因此，螺旋堆积的紧密性和NP蛋白中的蛋白水解裂解都不影响RNA与NP的结合或其免受RNA酶的保护。
Previous studies showed that the conformation of the paramyxovirus nucleocapsid varies extensively with regard to the flexibility and coiling of the helix, and changes of this type could be important for virus assembly and transcription of the viral RNA. The helix is tightly coiled and relatively inflexible at high salt concentration (e.g., 1.0 M NaCl) and loosely coiled or extended in low-salt buffer (0.01 M). It has now been found that a salt-induced conformational change can alter the accessibility of the Sendai virus nucleocapsid protein (NP, MW .apprx. 60,000) to cleavage by trypsin. When the nucleocapsid is tightly coiled, NP is cleaved to yield a single major cleavage product (t48, MW .apprx. 48,000) that contains the original N-terminus of the molecule. When the nucleocapsid is in the uncoiled state, t48 is further cleaved to a major N-terminal product, t34, and a 2nd product t15; t15 may be further cleaved to yield t12. Unlike the .apprx. 12,000 daltons of NP that is degraded to small peptides and lost from the nucleocapsid when NP is cleaved to t48, both t34 and t15 (or t12) remain associated with the nucleocapsid structure, although they are not disulfide bonded to each other. Sendai virus nucleocapsids containing t34 and t15 (or t12) have the same morphological appearance and respond reversibly to changes in salt concentration as do nucleocapsids composed of the native NP or t48. The properties of the NP subunit that are important in determining the helical conformation of the nucleocapsid thus reside in the N-terminal 48,000 daltons of the molecule and are unaffected by the further cleavages. In contrast to the conformation-dependent exposure of tryptic cleavage sites on NP, the viral RNA in the nucleocapsid is inaccessible to digestion by RNase regardless of salt-dependent changes in conformation or of the state of tryptic cleavage of NP. Thus, neither the tightness of stacking of the helix nor proteolytic cleavages in the NP protein affect the binding of the RNA to NP or its protection from RNase.