Reha-Krantz L J
Gene. 1992 Mar 1;112(1):133-7. doi: 10.1016/0378-1119(92)90315-g.
It was proposed by Bernad et al. [Cell 59 (1989) 219-228] and Blanco et al. [Gene 100 (1991) 27-38] that the 3'----5' exonuclease (Exo) domain of Escherichia coli DNA polymerase I (PolI) is structurally and functionally conserved among prokaryotic and eukaryotic DNA polymerases. The basis for this claim is the presence of three short peptide sequences in many DNA polymerases that resemble PolI sequences that have been shown by x-ray crystallographic and genetic engineering studies to be metal ion binding sites that are essential for PolI 3'----5' Exo activity [Derbyshire et al., Science 240 (1988) 199-201]. This claim is made even though there is little amino acid (aa) sequence similarity between PolI and many eukaryotic and viral DNA polymerases and in spite of significant differences in the amount of 3'----5' Exo activity in the DNA polymerases compared. For at least one DNA polymerase, bacteriophage T4 DNA polymerase, one of the proposed conserved Exo sequences does not appear to be important for 3'----5' Exo activity. This T4 DNA polymerase result provides a reminder that caution must be used when weak aa sequence similarities are used to predict protein structure and function.
伯纳特等人[《细胞》59卷（1989年）219 - 228页]以及布兰科等人[《基因》100卷（1991年）27 - 38页]提出，大肠杆菌DNA聚合酶I（PolI）的3'→5'核酸外切酶（Exo）结构域在原核生物和真核生物DNA聚合酶中在结构和功能上是保守的。这一说法的依据是，许多DNA聚合酶中存在三个短肽序列，它们类似于PolI序列，经X射线晶体学和基因工程研究表明这些序列是金属离子结合位点，对PolI的3'→5' Exo活性至关重要[德比郡等人，《科学》240卷（1988年）199 - 201页]。尽管PolI与许多真核生物和病毒DNA聚合酶之间氨基酸（aa）序列相似性很低，而且相比之下这些DNA聚合酶的3'→5' Exo活性量存在显著差异，但仍提出了这一说法。对于至少一种DNA聚合酶，即噬菌体T4 DNA聚合酶，其中一个被认为保守的Exo序列似乎对3'→5' Exo活性并不重要。T4 DNA聚合酶的这一结果提醒我们，当利用微弱的aa序列相似性来预测蛋白质结构和功能时必须谨慎。
