MOLECULAR SUBSTRUCTURE OF A VIRAL RECEPTOR-RECOGNITION PROTEIN - THE GP17 TAIL-FIBER OF BACTERIOPHAGE-T7
MOLECULAR SUBSTRUCTURE OF A VIRAL RECEPTOR-RECOGNITION PROTEIN - THE GP17 TAIL-FIBER OF BACTERIOPHAGE-T7
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DOI：
10.1016/0022-2836(88)90246-x
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发表时间：
1988-03-20
影响因子：
5.6
通讯作者：
STUDIER, FW
中科院分区：
文献类型：
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作者：
STEVEN, AC;TRUS, BL;STUDIER, FW
噬菌体T7尾部复合物由一个圆锥形尾管组成，周围是六个扭结尾纤维，它们是病毒蛋白GP17的低聚物（MR 61,400）。我们通过将二级结构预测与通过负相染色的尾部复合物的电子显微照片相关性获得的超微结构信息进行了将二级结构预测与超微结构信息进行了整合，从而得出了尾纤维的分子模型。通过对纯化纤维的高分辨率扫描透射电子显微镜，既有负染色和未染色）进一步完善了该模型。由后者图像制定的质量测量结果表明，纤维是GP17的三聚体。近端半纤维是一根均匀的杆，直径约2.0 nm，长16.4 nm，我们指的是三链盘绕圈，包含三个副本的.Alpha.-Hellical indical域，约为117个残基，在PHE151。远端半纤维长15.5 nm，由四个小球，直径为3.1至4.8 nm，在刚性线性阵列中：它包含组成型GP17的羧基末端两半（残基.apprx。268至553）链条在其长轴周围以3倍对称性排列。氨基末端结构域（残基1至149）将纤维连接到尾管。我们得出的结论是，三个gp17链在近端半纤维中是准等效的，在远端半纤维中等效，而在分离两个半纤维的扭结区域中是非等效的：这种局部的非等效性可能代表A在分段的同源蛋白中形成扭结关节的一般机制。
The bacteriophage T7 tail complex consists of a conical tail-tube surrounded by six kinked tail-fibers, which are oligomers of the viral protein gp17 (Mr 61,400). We have derived a molecular model for the tail-fiber by integrating secondary structure predictions with ultrastructural information obtained by correlation averaging of electron micrographs of negatively stained tail complexes. This model has been further refined by high-resolution scanning transmission electron microscopy of purified fibers, both negatively stained and unstained. Mass measurements made from the latter images establish that the fiber is a trimer of gp17. The proximal half-fiber is a uniform rod, about 2.0 nm in diameter and 16.4 nm long, which we refer to be a triple-stranded coiled-coil, containing three copies of an .alpha.-helical domain of about 117 residues, starting at Phe151. The distal half-fiber is 15.5 nm long, and is made up of four globules, 3.1 to 4.8 nm in diameter, in rigid linear array: it contains the carboxy-terminal halves (residues .apprx. 268 to 553) of the constituent gp17 chains, arranged with 3-fold symmetry around its long axis. The amino-terminal domains (residues 1 to 149) link the fiber to the tail-tube. We conclude that the three gp17 chains are quasi-equivalent in the proximal half-fiber, equivalent in the distal half-fiber, and non-equivalent in the kink region that separates the two half-fibers: such localized non-equivalence may represent a general mechanism for the formation of kinked joints in segmented homo-oligomeric proteins.