Gläsner W, Merkl R, Schellenberger V, Fritz H J
Institut für Molekulare Genetik, Georg-August-Universität, Göttingen, Germany.
J Mol Biol. 1995 Jan 6;245(1):1-7. doi: 10.1016/s0022-2836(95)80033-6.
The substrate spectrum of Vsr DNA mismatch endonuclease of Escherichia coli K-12 was investigated using fluorescence-labelled oligonucleotide substrates and a DNA sequencer for detection and quantification of substrates and reaction products. Fourteen substrates were found to be processed by the enzyme, which differ in one or two positions from the canonical pentanucleotide sequence CTA/TGG (T mismatched to G). Relative second-order rate constants of these substrates were determined in groups of four by multiple substrate kinetics and compared to the underresentation of the corresponding pentanucleotides in the E. coli K-12 genome. The high quality of correlation further establishes active mutagenesis by VSP repair as a significant driving force of the evolution of the E. coli K-12 genome and provides clues to its possible selective value.
利用荧光标记的寡核苷酸底物和DNA测序仪来检测和定量底物及反应产物，对大肠杆菌K-12的Vsr DNA错配内切核酸酶的底物谱进行了研究。发现该酶可作用于14种底物，这些底物与典型的五核苷酸序列CTA/TGG（T与G错配）在一个或两个位置上有所不同。通过多底物动力学对这14种底物按4个一组测定其相对二级速率常数，并与大肠杆菌K-12基因组中相应五核苷酸的低丰度进行比较。这种高度的相关性进一步证实了VSP修复介导的活性诱变是大肠杆菌K-12基因组进化的一个重要驱动力，并为其可能的选择价值提供了线索。
