Single phage T4 DNA packaging motors exhibit barge force generation, high velocity, and dynamic variability
Single phage T4 DNA packaging motors exhibit barge force generation, high velocity, and dynamic variability
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DOI：
10.1073/pnas.0704008104
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发表时间：
2007-10-23
影响因子：
11.1
通讯作者：
Smith, Douglas E.
中科院分区：
文献类型：
--
作者：
Fuller, Derek N.;Raymer, Dorian M.;Smith, Douglas E.
终止酶复合物，促进ATP驱动的DNA包装在大肠杆菌和许多真核病毒中，构成了一个广泛的和潜在的不同家庭的分子马达的动力学或机械信息很少。在这里，我们报告的光镊测量单个DNA分子包装动力学噬菌体T4，一个大的，尾大肠杆菌病毒，是一个重要的模型系统在分子生物学。我们发现，空的prohead和大的末端酶蛋白（gp 17），可以捕获和开始包装靶DNA分子在几秒钟内，从而证明了一个独特的病毒装配途径之间形成的复合物。马达产生> 60 pN的力，类似于用噬菌体029测量的力，表明高力产生是病毒DNA包装马达的共同特性。然而，T4的DNA易位率明显高于029，平均约为700 bp/s，范围高达约2,000 bp/s，与噬菌体T4在300 s（-1）内包装巨大的171-kb基因组一致< 10 min during viral infection and implying high ATIP turnover rates of >。电机速度随施加的负载而降低，但在45 pN时平均为320 bp/s，表明发电量非常高。有趣的是，电机也表现出大的动态变化的速度，这表明它可以承担多个积极的构象状态齿轮不同的易位率。除了观察到的可逆暂停和滑动能力之外，这种能力还可能使噬菌体T4能够协调DNA包装与其他正在进行的过程，包括病毒DNA转录、重组和修复。
Terminase enzyme complexes, which facilitate ATP-driven DNA packaging in phages and in many eukaryotic viruses, constitute a wide and potentially diverse family of molecular motors about which little dynamic or mechanistic information is available. Here we report optical tweezers measurements of single DNA molecule packaging dynamics in phage T4, a large, tailed Escherichia coli virus that is an important model system in molecular biology. We show that a complex is formed between the empty prohead and the large terminase protein (gp17) that can capture and begin packaging a target DNA molecule within a few seconds, thus demonstrating a distinct viral assembly pathway. The motor generates forces > 60 pN, similar to those measured with phage 029, suggesting that high force generation is a common property of viral DNA packaging motors. However, the DNA translocation rate for T4 was strikingly higher than that for 029, averaging approximate to 700 bp/s and ranging up to approximate to 2,000 bp/s, consistent with packaging by phage T4 of an enormous, 171-kb genome in < 10 min during viral infection and implying high ATIP turnover rates of > 300 s(-1). The motor velocity decreased with applied load but averaged 320 bp/s at 45 pN, indicating very high power generation. Interestingly, the motor also exhibited large dynamic changes in velocity, suggesting that it can assume multiple active conformational states gearing different translocation rates. This capability, in addition to the reversible pausing and slipping capabilities that were observed, may allow phage T4 to coordinate DNA packaging with other ongoing processes, including viral DNA transcription, recombination, and repair.