Molineux I J
Molecular Genetics and Microbiology, University of Texas, Austin, TX 78712-1095, USA.
Mol Microbiol. 2001 Apr;40(1):1-8. doi: 10.1046/j.1365-2958.2001.02357.x.
Development of a sensitive assay that measures the rate of cellular internalization of an infecting bacteriophage T7 genome has led to surprising observations on the initiation of infection. Proteins ejected from the phage virion probably function as an extensible tail to form a channel across the cell envelope. This channel is subsequently used for translocating the phage genome into the cell. One of these ejected proteins also controls the amount of DNA that enters the cell, rendering subsequent internalization of the remainder of the genome dependent on transcription. Mutations affecting this protein allow the entire phage genome to enter a cell by the transcription-independent process. This process exhibits pseudo-zero-order reaction kinetics and a temperature dependence of translocation rate that are not expected if DNA ejection from a phage capsid were caused by a physical process. The temperature dependence of transcription-independent T7 DNA translocation rate is similar to those of enzyme-catalysed reactions. Current data suggest a highly speculative model, in which two of the proteins ejected from the phage head establish a molecular motor that ratchets the phage genome into the cell.
一种用于测量感染性噬菌体T7基因组细胞内化速率的灵敏检测方法的开发，带来了关于感染起始的惊人发现。从噬菌体病毒粒子中排出的蛋白质可能起到可延伸尾巴的作用，从而形成一个穿过细胞膜的通道。这个通道随后被用于将噬菌体基因组转运到细胞内。其中一种排出的蛋白质还控制进入细胞的DNA量，使得基因组其余部分随后的内化依赖于转录。影响这种蛋白质的突变使得整个噬菌体基因组能够通过不依赖转录的过程进入细胞。这个过程表现出假零级反应动力学以及转运速率对温度的依赖性，如果噬菌体衣壳中的DNA排出是由物理过程引起的，那么这些特性是不符合预期的。不依赖转录的T7 DNA转运速率对温度的依赖性与酶催化反应的相似。目前的数据提出了一个极具推测性的模型，其中从噬菌体头部排出的两种蛋白质形成了一个分子马达，将噬菌体基因组逐步推进细胞内。
