Two-metal versus one-metal mechanisms of lysine adenylylation by ATP-dependent and NAD(+)-dependent polynucleotide ligases Journal Article
| Authors: | Unciuleac, M. C.; Goldgur, Y.; Shuman, S. |
| Article Title: | Two-metal versus one-metal mechanisms of lysine adenylylation by ATP-dependent and NAD(+)-dependent polynucleotide ligases |
| Abstract: | Polynucleotide ligases comprise a ubiquitous superfamily of nucleic acid repair enzymes that join 3′-OH and 5′-PO4 DNA or RNA ends. Ligases react with ATP or NAD+ and a divalent cation cofactor to form a covalent enzyme-(lysine-Nζ)-adenylate intermediate. Here, we report crystal structures of the founding members of the ATP-dependent RNA ligase family (T4 RNA ligase 1; Rnl1) and the NAD+-dependent DNA ligase family (Escherichia coli LigA), captured as their respective Michaelis complexes, which illuminate distinctive catalytic mechanisms of the lysine adenylylation reaction. The 2.2-Å Rnl1·ATP·(Mg2+)2 structure highlights a two-metal mechanism, whereby: a ligase-bound "catalytic" Mg2+ (H2O)5 coordination complex lowers the pKa of the lysine nucleophile and stabilizes the transition state of the ATP α phosphate; a second octahedral Mg2+ coordination complex bridges the β and γ phosphates; and protein elements unique to Rnl1 engage the γ phosphate and associated metal complex and orient the pyrophosphate leaving group for in-line catalysis. By contrast, the 1.55-Å LigA·NAD+·Mg2+ structure reveals a one-metal mechanism in which a ligase-bound Mg2+(H2O)5 complex lowers the lysine pKa and engages the NAD+ α phosphate, but the β phosphate and the nicotinamide nucleoside of the nicotinamide mononucleotide (NMN) leaving group are oriented solely via atomic interactions with protein elements that are unique to the LigA clade. The two-metal versus one-metal dichotomy demarcates a branchpoint in ligase evolution and favors LigA as an antibacterial drug target. © 2017, National Academy of Sciences. All rights reserved. |
| Keywords: | covalent nucleotidyltransferase; lysyl-amp; metal catalysis |
| Journal Title: | Proceedings of the National Academy of Sciences of the United States of America |
| Volume: | 114 |
| Issue: | 10 |
| ISSN: | 0027-8424 |
| Publisher: | National Academy of Sciences |
| Date Published: | 2017-03-07 |
| Start Page: | 2592 |
| End Page: | 2597 |
| Language: | English |
| DOI: | 10.1073/pnas.1619220114 |
| PROVIDER: | scopus |
| PMCID: | PMC5347617 |
| PUBMED: | 28223499 |
| DOI/URL: | |
| Notes: | Article -- Export Date: 3 April 2017 -- Source: Scopus |
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