Son M, Hayes S J, Serwer P
Department of Biochemistry, University of Texas Health Science Center, San Antonio 78284-7760.
Gene. 1989 Oct 30;82(2):321-5. doi: 10.1016/0378-1119(89)90058-9.
The in vitro DNA packaging of several DNA bacteriophages is stimulated by the presence of neutral polymers. To optimize bacteriophage T7 DNA packaging and to understand the basis for optimization, the efficiency of T7 DNA packaging has been determined at completion, as a function of the type, molecular mass, and concentration of the polymer added. When the polymer used was polyethylene glycol (PEG) of 0.2, 0.6 or 12.6 kDa, the efficiency of DNA packaging reached maximum at an intermediate concentration of polymer. The osmotic pressure (Pos) at maximum efficiency was either in, or close to, the range of colloid Pos measured for the intact host cell. The optimum Pos increased as the size of the polymer used decreased. PEG-100 (of 0.1 kDa) did not stimulate in vitro T7 DNA packaging. Dextran of 10 kDa also stimulated packaging and produced maximum efficiency at a physiological Pos. The degree of stimulation increases as DNA packaging extract concentration decreases; stimulation by as much as two to three orders of magnitude is observed. The presence of added polymer reduces fluctuations in DNA packaging efficiency caused by variability in the concentration of DNA packaging extracts. For reproducible and high efficiency packaging, the dextran was more reliable than the PEGs, possibly because the Pos of the dextran solutions is less sensitive to polymer concentration than is the Pos of PEG solutions. The optimum concentration of dextran at completion was also the optimum at all times before completion.
几种DNA噬菌体的体外DNA包装受到中性聚合物的刺激。为了优化噬菌体T7 DNA包装并理解优化的基础，已测定了T7 DNA包装在完成时的效率，该效率是添加的聚合物的类型、分子量和浓度的函数。当使用的聚合物是0.2、0.6或12.6 kDa的聚乙二醇（PEG）时，DNA包装效率在聚合物的中间浓度时达到最大值。最大效率时的渗透压（Pos）处于或接近完整宿主细胞测量的胶体Pos范围。随着所用聚合物尺寸的减小，最佳Pos增加。0.1 kDa的PEG - 100不刺激体外T7 DNA包装。10 kDa的葡聚糖也刺激包装并在生理Pos时产生最大效率。刺激程度随着DNA包装提取物浓度的降低而增加；观察到刺激高达两到三个数量级。添加聚合物的存在减少了由DNA包装提取物浓度变化引起的DNA包装效率的波动。为了实现可重复和高效的包装，葡聚糖比PEG更可靠，这可能是因为葡聚糖溶液的Pos对聚合物浓度的敏感性低于PEG溶液的Pos。完成时葡聚糖的最佳浓度在完成前的所有时间也是最佳的。
