Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada.
Nucleic Acids Res. 2011 Sep 1;39(17):7620-9. doi: 10.1093/nar/gkr397. Epub 2011 Jun 15.
Reverse transcriptases (RTs) are RNA-dependent DNA polymerases that usually function in the replication of selfish DNAs such as retrotransposons and retroviruses. Here, we have biochemically characterized a RT-related protein, AbiK, which is required for abortive phage infection in the Gram-positive bacterium Lactococcus lactis. In vitro, AbiK does not exhibit the properties expected for an RT, but polymerizes long DNAs of 'random' sequence, analogous to a terminal transferase. Moreover, the polymerized DNAs appear to be covalently attached to the AbiK protein, presumably because an amino acid serves as a primer. Mutagenesis experiments indicate that the polymerase activity resides in the RT motifs and is essential for phage resistance in vivo. These results establish a novel biochemical property and a non-replicative biological role for a polymerase.
逆转录酶（RTs）是一种依赖 RNA 的 DNA 聚合酶，通常在逆转录转座子和逆转录病毒等自私 DNA 的复制中发挥作用。在这里，我们对一种与逆转录酶相关的蛋白 AbiK 进行了生化特性分析，该蛋白是革兰氏阳性菌乳球菌中噬菌体感染失败所必需的。体外实验表明，AbiK 不具有预期的逆转录酶特性，但能聚合“随机”序列的长 DNA，类似于末端转移酶。此外，聚合的 DNA 似乎与 AbiK 蛋白共价连接，可能是因为一个氨基酸充当引物。突变实验表明，聚合酶活性位于 RT 基序中，对体内噬菌体抗性至关重要。这些结果为聚合酶确立了一种新的生化特性和非复制性的生物学作用。
