Abstract：
MutT proteins belong to the Nudix hydrolase superfamily that includes a diverse group of Mg2+ requiring enzymes. These proteins use a generalized substrate, nucleoside diphosphate linked to a chemical group X (NDP-X), to produce nucleoside monophosphate (NMP) and the moiety X linked with phosphate (XP). E. coli MutT (EcoMutT) and mycobacterial MutT1 (MsmMutT1) belong to the Nudix hydrolase superfamily that utilize 8-oxo-(d)GTP (referring to both 8-oxo-GTP or 8-oxo-dGTP). However, predominant products of their activities are different. While EcoMutT produces 8-oxo-(d)GMP, MsmMutT1 gives rise to 8-oxo-(d)GDP. Here, we show that the altered cleavage specificities of the two proteins are largely a consequence of the variation at the equivalent of Gly37 (G37) in EcoMutT to Lys (K65) in the MsmMutT1. Remarkably, mutations of G37K (EcoMutT) and K65G (MsmMutT1) switch their cleavage specificities to produce 8-oxo-(d)GDP, and 8-oxo-(d)GMP, respectively. Further, a time course analysis using 8-oxo-GTP suggests that MsmMutT1(K65G) hydrolyses 8-oxo-(d)GTP to 8-oxo-(d)GMP in a two-step reaction via 8-oxo-(d)GDP intermediate. Expectedly, unlike EcoMutT (G37K) and MsmMutT1, EcoMutT and MsmMutT1 (K65G) rescue an E. coli ΔmutT strain, better by decreasing A to C mutations.
摘要：
MutT蛋白属于Nudix水解酶超家族，包括一组不同的需要Mg2的酶。这些蛋白质使用广义的底物，连接到化学基团X（NDP-X）的核苷二磷酸，以产生核苷单磷酸酯(NMP)和与磷酸酯(XP)连接的部分X。大肠杆菌MutT(EcoMutT)和分枝杆菌MutT1(MsmMutT1)属于利用8-氧代-(d)GTP(指8-氧代-GTP或8-氧代-dGTP)的Nudix水解酶超家族。然而,他们活动的主要产品是不同的。虽然EcoMutT产生8-oxo-（d）GMP，MsmMutT1产生8-氧代-(d)GDP。这里,我们表明，这两种蛋白质的切割特异性改变在很大程度上是EcoMutT中的Gly37（G37）与MsmMutT1中的Lys（K65）的等效变异的结果。值得注意的是,G37K（EcoMutT）和K65G（MsmMutT1）的突变将其切割特异性转换为产生8-oxo-（d）GDP，和8-氧代-(d)GMP，分别。Further,使用8-氧代-GTP的时程分析表明，MsmMutT1（K65G）通过8-氧代-（d）GDP中间体在两步反应中将8-氧代-（d）GTP水解为8-氧代-（d）GMP。期望,与EcoMutT（G37K）和MsmMutT1不同，EcoMutT和MsmMutT1（K65G）拯救了大肠杆菌ΔmutT菌株，通过减少A到C突变更好。
