Structural insights into the specificity and catalytic mechanism of mycobacterial nucleotide pool sanitizing enzyme MutT2

Publication date: Available online 9 October 2018Source: Journal of Structural BiologyAuthor(s): Amandeep Singh, Sheikh Mohammad Arif, Pau Biak Sang, Umesh Varshney, M. VijayanAbstractMis-incorporation of modified nucleotides, such as 5-methyl-dCTP or 8-oxo-dGTP, in DNA can be detrimental to genomic integrity. MutT proteins are sanitization enzymes which function by hydrolyzing such nucleotides and regulating the pool of free nucleotides in the cytoplasm. Mycobacterial genomes have a set of four MutT homologs, namely, MutT1, MutT2, MutT3 and MutT4. Mycobacterial MutT2 hydrolyzes 5m-dCTP and 8-oxo-dGTP to their respective monophosphate products. Additionally, it can hydrolyze canonical nucleotides dCTP and CTP, with a suggested role in sustaining their optimal levels in the nucleotide pool. The structures of M. smegmatis MutT2 and its complexes with cytosine derivates have been determined at resolutions ranging from 1.10 Å to 1.73 Å. The apo enzyme and its complexes with products (dCMP, CMP and 5m-dCMP) crystallize in space group P21212, while those involving substrates (dCTP, CTP and 5m-dCTP) crystallize in space group P21. The molecule takes an α/β/α sandwich fold arrangement, as observed in other MutT homologs. The nucleoside moiety of the ligands is similarly located in all the complexes, while the location of the remaining tail exhibits variability. This is the first report of a MutT2-type protein in complex with ligands. A critical interaction involving Asp116 confe...

Source: Journal of Structural Biology - October 11, 2018 Category: Biology Source Type: research