ASSEMBLY OF BACTERIOPHAGE-T7 - DIMENSIONS OF THE BACTERIOPHAGE AND ITS CAPSIDS
ASSEMBLY OF BACTERIOPHAGE-T7 - DIMENSIONS OF THE BACTERIOPHAGE AND ITS CAPSIDS
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DOI：
10.1016/s0006-3495(81)84763-7
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发表时间：
1981-01-01
影响因子：
3.4
通讯作者：
ROSS, MJ
中科院分区：
文献类型：
--
作者：
STROUD, RM;SERWER, P;ROSS, MJ
通过小角 X 射线散射研究噬菌体 T7 和 T7 衣壳的尺寸。噬菌体 T7 的行为就像一个外半径为 301.+- 的均匀密度的球体。 2.ANG。 （不包括噬菌体尾部），蛋白质加核酸的计算体积为 1.14.+-。 0.05 倍10-16 毫升。溶液中 T7 噬菌体的外半径测定为 .apprx。比电子显微照片测量的半径大 30%，这表明在准备 EM 期间发生了相当大的收缩。具有噬菌体样包膜且不含 DNA 的衣壳是从 T7 感染的大肠杆菌裂解物（衣壳 II）中获得的，并通过温度冲击将 T7 噬菌体的衣壳成分与噬菌体 DNA 分离（衣壳 IV）。在这两种情况下，峰值蛋白质密度均位于半径 275 埃处；外半径为 286 .+-。 4.ANG.，.近似。比T7噬菌体的包膜小5%。衣壳II的包膜厚度为22.+-。 4.ANG.，与估计的蛋白质厚度23.+-一致。 5.ANG。在整个 T7 噬菌体中，如电子显微照片所示，内部 DNA 呈阳性染色。 T7 噬菌体中可用于包装 DNA 的体积估计为 9.2 .+-。 0.4 倍10-17 毫升。包装的DNA采用23.6.ANG的常规包装。 DNA 链之间的晶面间距。 23.6 ANG 的角宽度。反射显示整个噬菌体头部的平均 DNA-DNA 间距为 27.5 .+-。 < 2.2.ANG.. 当在超速离心机中进行 X 射线散射沉淀时，T7 前体衣壳（衣壳 I）膨胀至与衣壳 II 和 IV 基本相同的外部尺寸。衣壳 I 的这种扩张可以通过用戊二醛固定来防止；固定衣壳 I 在半径 247ANG 处具有峰值密度，比衣壳 II 或 IV 低 10%。
The dimensions of bacteriophage T7 and T7 capsids were investigated by small angle X-ray scattering. Phage T7 behaves like a sphere of uniform density with an outer radius of 301 .+-. 2 .ANG. (excluding the phage tail) and a calculated volume for protein plus nucleic acid of 1.14 .+-. 0.05 .times. 10-16 ml. The outer radius determined for T7 phage in solution is .apprx. 30% greater than the radius measured from electron micrographs, which indicates that considerable shrinkage occurs during preparation for EM. Capsids that have a phage-like envelope and do not contain DNA were obtained from lysates of T7-infected Escherichia coli (capsid II) and by separating the capsid component of T7 phage from the phage DNA by means of temperature shock (capsid IV). In both cases the peak protein density is at a radius of 275 .ANG.; the outer radius is 286 .+-. 4 .ANG., .apprx. 5% smaller than the envelope of T7 phage. The thickness of the envelope of capsid II is 22 .+-. 4 .ANG., consistent with the thickness of protein estimated to be 23 .+-. 5 .ANG. in whole T7 phage, as seen on electron micrographs in which the internal DNA is positively stained. The volume in T7 phage available to package DNA is estimated to be 9.2 .+-. 0.4 .times. 10-17 ml. The packaged DNA adopts a regular packing with 23.6 .ANG. interplanar spacing between DNA strands. The angular width of the 23.6 .ANG. reflection shows that the mean DNA-DNA spacing throughout the phage head is 27.5 .+-. < 2.2 .ANG.. A T7 precursor capsid (capsid I) expands when pelleted for X-ray scattering in the ultracentrifuge to essentially the same outer dimensions as for capsids II and IV. This expansion of capsid I can be prevented by fixing with glutaraldehyde; fixed capsid I has peak density at a radius of 247.ANG., 10% less than capsid II or IV.