Yang Wei
Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, 9000 Rockville Pike, Building 5, Room B1-03 Bethesda, Maryland 20892, USA.
Nat Struct Mol Biol. 2008 Nov;15(11):1228-31. doi: 10.1038/nsmb.1502. Epub 2008 Oct 26.
Nucleotidyl-transfer enzymes, which synthesize, degrade and rearrange DNA and RNA, often depend on metal ions for catalysis. All DNA and RNA polymerases, MutH-like or RNase H-like nucleases and recombinases, and group I introns seem to require two divalent cations to form a complete active site. The two-metal-ion mechanism has been proposed to orient the substrate, facilitate acid-base catalysis and allow catalytic specificity to exceed substrate binding specificity attributable to the stringent metal-ion (Mg2+ in particular) coordination. Not all nucleotidyl-transfer enzymes use two metal ions for catalysis, however. The betabetaalpha-Me and HUH nucleases depend on a single metal ion in the active site for the catalysis. All of these one- and two metal ion-dependent enzymes generate 5'-phosphate and 3'-OH products. Structural and mechanistic comparisons show that these seemingly unrelated nucleotidyl-transferases share a functionally equivalent metal ion.
核苷酸转移酶负责DNA和RNA的合成、降解及重排，其催化过程通常依赖金属离子。所有的DNA和RNA聚合酶、MutH样或RNase H样核酸酶及重组酶，还有I类内含子，似乎都需要两个二价阳离子来形成完整的活性位点。双金属离子机制被认为可使底物定向、促进酸碱催化，并使催化特异性超过归因于严格金属离子（特别是Mg2+）配位的底物结合特异性。然而，并非所有核苷酸转移酶都利用双金属离子进行催化。ββα-Me核酸酶和HUH核酸酶在活性位点依赖单个金属离子进行催化。所有这些依赖单金属离子和双金属离子的酶都会产生5'-磷酸和3'-羟基产物。结构和机制比较表明，这些看似不相关的核苷酸转移酶共享功能等效的金属离子。
