Haywood A M
Proc Natl Acad Sci U S A. 1973 Aug;70(8):2381-5. doi: 10.1073/pnas.70.8.2381.
Escherichia coli membranes were isolated in the presence of 6 mM Mg(++). They were washed with buffer containing no Mg(++) to yield a fraction containing material bound only in the presence of divalent cations, "membrane eluate," and that bound in the absence of divalent cations, "membrane." When E. coli infected with bacteriophage MS2 are labeled with [(14)C]uracil, all MS2 replicative RNA, i.e., the RNA species containing MS2 complementary RNA, is in the membrane eluate and membrane. The amount of [(14)C]uracil in replicative RNA found in the membrane eluate increases with time of labeling, whereas that in the replicative RNA in the membrane reaches a plateau in 1-2 min. This finding is consistent with a precursor-product relationship. Most of the label entering single-stranded viral RNA comes from the replicative RNA in the membrane eluate. This result suggests that polymerase components or factors required for complementary-strand synthesis are bound to membrane even in the absence of divalent cations and that the polymerase is no longer bound to these factors when it is making the bulk of the progeny single-stranded RNA.
在6 mM Mg(++)存在的情况下分离大肠杆菌膜。用不含Mg(++)的缓冲液洗涤它们，以产生一个组分，其中包含仅在二价阳离子存在时结合的物质，即“膜洗脱液”，以及在不存在二价阳离子时结合的物质，即“膜”。当用[(14)C]尿嘧啶标记感染噬菌体MS2的大肠杆菌时，所有MS2复制RNA，即含有MS2互补RNA的RNA种类，都存在于膜洗脱液和膜中。膜洗脱液中复制RNA中[(14)C]尿嘧啶的含量随标记时间增加，而膜中复制RNA中的[(14)C]尿嘧啶在1 - 2分钟内达到平稳期。这一发现与前体-产物关系一致。进入单链病毒RNA的大部分标记来自膜洗脱液中的复制RNA。这一结果表明，即使在不存在二价阳离子的情况下，互补链合成所需的聚合酶组分或因子也与膜结合，并且当聚合酶合成大部分子代单链RNA时，它不再与这些因子结合。
