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An unprecedented mechanism of nucleotide methylation in organisms containing thyX
Journal article   Open access   Peer reviewed

An unprecedented mechanism of nucleotide methylation in organisms containing thyX

Tatiana V. Mishanina, Liping Yu, Kalani Karunaratne, Dibyendu Mondal, John M. Corcoran, Michael A. Choi and Amnon Kohen
Science (American Association for the Advancement of Science), Vol.351(6272), pp.507-510
01/29/2016
DOI: 10.1126/science.aad0300
PMCID: PMC4744818
PMID: 26823429
url
https://doi.org/10.1126/science.aad0300View
Published (Version of record) Open Access

Abstract

In several human pathogens, thyX-encoded flavin-dependent thymidylate synthase (FDTS) catalyzes the last step in the biosynthesis of thymidylate, one of the four DNA nucleotides. ThyX is absent in humans, rendering FDTS an attractive antibiotic target; however, the lack of mechanistic understanding prohibits mechanism-based drug design. Here, we report trapping and characterization of two consecutive intermediates, which together with previous crystal structures indicate that the enzyme's reduced flavin relays a methylene from the folate carrier to the nucleotide acceptor. Furthermore, these results corroborate an unprecedented activation of the nucleotide that involves no covalent modification but only electrostatic polarization by the enzyme's active site. These findings indicate a mechanism that is very different from thymidylate biosynthesis in humans, underscoring the promise of FDTS as an antibiotic target.
Multidisciplinary Sciences Science & Technology Science & Technology - Other Topics

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