DOMAIN-STRUCTURE OF BACTERIOPHAGE FD ADSORPTION PROTEIN
DOMAIN-STRUCTURE OF BACTERIOPHAGE FD ADSORPTION PROTEIN
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DOI：
10.1016/0014-5793(81)80969-6
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发表时间：
1981-01-01
期刊：
影响因子：
3.5
通讯作者：
WALKER, JE
中科院分区：
文献类型：
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作者：
ARMSTRONG, J;PERHAM, RN;WALKER, JE
噬菌体fd是一组密切相关的丝状雄性特异性噬菌体之一（其他是m13和fl）。病毒粒子由一个封闭的DNA单链环组成，长度为[1]，有6408个核苷酸，位于2700个外壳蛋白[2]亚基的管状阵列中。在病毒丝的一端有约5个第二蛋白拷贝，即吸附蛋白或a蛋白[3]；还有2或3个其他较小的蛋白质的少数拷贝[4,5]。人们对病毒的生命周期了解甚多（回顾[6]）。a蛋白是噬菌体吸附到宿主受体所必需的，宿主受体可能是f -菌毛的顶端。用枯草菌素蛋白酶处理噬菌体导致a蛋白被消化，而不是外壳蛋白，留下一个稳定但不具有传染性的颗粒[7,8]。电子显微镜显示，这种粒子已经失去了位于原生病毒粒子[9]一端的几个小的球形结构。通过将蛋白质[3]的n端残基与噬菌体的翻译DNA序列比对，推断出a蛋白的氨基酸序列[1,10]。由于a蛋白的低丰度（约占病毒的1%）和极难溶解性，对其结构及其在宿主细胞上吸附作用的进一步分析受到了阻碍；分离该蛋白需要用洗涤剂使病毒完全变性[3,4]。在这里，我们发现用枯草菌素温和地消化噬菌体fd会释放出一个大的、可溶的a蛋白n端片段。该片段似乎与完整的噬菌体竞争宿主细胞上的附着位点。这些结果提出了结构的模型
Bacteriophage fd is one of a group of closely-related filamentous male-specific coliphages (others are M 13 and fl). The virion consists of a closed single-stranded loop of DNA, 6408 nucleotides in length [1], within a tubular array of 2700 subunits of coat protein [2]. At one end of the viral filament are~ 5 copies of a second protein, the adsorption protein or A-protein [3]; there are also a few copies of 2 or 3 other, smaller proteins [4, 5]. Much is known about the life cycle of the virus (review [6]).The A-protein is required for adsorption of the phage to the host receptor, which is probably the tip of the F-pilus [7]. Treatment of the phage with the proteinase subtilisin results in digestion of the A-protein but not the coat protein, leaving a particle which is stable but not infectious [7, 8]. Electron microscopy reveals that such a particle has lost several small knoblike structures located at one end of the native virion [9]. The amino acid sequence of the A-protein has been deduced by alignment of the N-terminal residues of the protein [3] with the translated DNA sequence of the phage [1, 10]. Further analysis of the structure of the A-protein, and its role in adsorption to the host cell, has been hindered by its low abundance (~ 1% of the virus (w/w)) and its extreme insolubility; isolation of the protein requires complete denaturation of the virus with detergent [3, 4]. Here, we show that mild digestion of phage fd with subtilisin releases a large, soluble N-terminal fragment of the A-protein. The fragment appears to compete with intact phage for attachment sites on the host cell. These results suggest models for the structure of