1
|
Amini SK, Bashirbanaem P. Evidences for reaction mechanism of 9DB1 DNA catalyst. Int J Biol Macromol 2023; 253:126710. [PMID: 37690649 DOI: 10.1016/j.ijbiomac.2023.126710] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2023] [Revised: 08/29/2023] [Accepted: 09/03/2023] [Indexed: 09/12/2023]
Abstract
The first reported reaction mechanism of a DNAzyme, i.e. 9DB1, by using molecular dynamics (MD) simulations includes some ambiguities. We try to overcome some of these ambiguous aspects such as the role of mono and divalent metal ions and observed metal rescue effects by surveying the role of functional groups of original 9DB1 and a variety of its rate conserving and rate decreasing mutations via MD simulations. Conformational differences of these two distinct groups are responsible for their opposite rate trends. Blocking of the OH3' of acceptor nucleotide from effective attack by its hydrogen bond to O4' of donor nucleotide is observed in rate decreasing mutations. Our simulations manifest the role of Na+ and Mg2+ ions in bringing close to each other the ligated atoms. These findings along with observed conformational changes explain carefully the reported metal rescue effects for some phosphate groups.
Collapse
Affiliation(s)
- Saeed K Amini
- Chemistry and Chemical Engineering Research Centre of Iran, Tehran, Iran.
| | | |
Collapse
|
2
|
Parra-Meneses V, Rojas-Hernández F, Cepeda-Plaza M. The role of Na + in catalysis by the 8-17 DNAzyme. Org Biomol Chem 2022; 20:6356-6362. [PMID: 35856910 DOI: 10.1039/d2ob01075e] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The 8-17 DNAzyme is the most studied deoxyribozyme in terms of its molecular mechanism; hence it has become a model system to understand the basis behind DNA catalysis. New functional studies and the recent attainment of high-resolution X-ray structures, in addition to theoretical calculations have offered a great opportunity to gain a broader comprehension of its mechanism; however many aspects are unclear yet, especially regarding the precise role of metal ions in catalysis. Recently, molecular dynamics simulations have suggested for the first time a specific and dynamical participation of Na+ in the mechanism through the reaction pathway, besides the roles proposed for divalent metal cofactors. Herein, we present experimental evidence of a cooperative role of the monovalent cation Na+ in catalysis that is in line with these theoretical suggestions. Our findings show a clear influence of the concentration of Na+ on the activity of the 8-17 DNAzyme when Pb2+ is used as the cofactor. Interestingly, this effect is not noticed with Mg2+, indicating a particular contribution of the monovalent ion to catalysis that would operate preferentially with Pb2+. We have also found that Na+ affects the pKa of the general base and the general acid, indicating its influence on general acid-base catalysis, already identified as part of the mechanism of the 8-17 DNAzyme. Finally, our results emphasize the need to consider Na+ carefully in the design and analysis of functional studies of catalytic DNAs and its possible specific role in their mechanisms.
Collapse
|
3
|
Zhang W, Li Y, Du S, Chai Z, He J. Activation of 8-17 DNAzyme with extra functional group at conserved residues is related to catalytic metal ion. Bioorg Med Chem Lett 2021; 48:128234. [PMID: 34214510 DOI: 10.1016/j.bmcl.2021.128234] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2021] [Revised: 06/05/2021] [Accepted: 06/25/2021] [Indexed: 11/29/2022]
Abstract
In 8-17 DNAzyme, the end loop A6G7C8 is a highly conserved motif. Here we reported an activation approach by specific chemical modifications on A6 and C8 for more efficient Ca2+-mediated reaction. The importance of the end loop was further highlighted and its critical conservation broken for more powerful catalysts.
Collapse
Affiliation(s)
- Wenjie Zhang
- School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
| | - Yang Li
- State Key Laboratory of Toxicology and Medical Countermeasures, Beijing Institute of Pharmacology & Toxicology, Beijing 100850, China
| | - Shanshan Du
- State Key Laboratory of Toxicology and Medical Countermeasures, Beijing Institute of Pharmacology & Toxicology, Beijing 100850, China
| | - Zhilong Chai
- State Key Laboratory of Toxicology and Medical Countermeasures, Beijing Institute of Pharmacology & Toxicology, Beijing 100850, China
| | - Junlin He
- State Key Laboratory of Toxicology and Medical Countermeasures, Beijing Institute of Pharmacology & Toxicology, Beijing 100850, China.
| |
Collapse
|
4
|
Cortés-Guajardo C, Rojas-Hernández F, Paillao-Bustos R, Cepeda-Plaza M. Hydrated metal ion as a general acid in the catalytic mechanism of the 8-17 DNAzyme. Org Biomol Chem 2021; 19:5395-5402. [PMID: 34047747 DOI: 10.1039/d1ob00366f] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The RNA-cleaving 8-17 DNAzyme, which is a metalloenzyme that depends on divalent metal ions for its function, is the most studied catalytic DNA in terms of its mechanism. By the end of 2017, a report of the crystal structure of the enzyme-substrate complex in the presence of Pb2+ probed some of the previous findings and opened new questions, especially around the participation of the metal ion in the catalytic mechanism and the promiscuity exhibited by the enzyme in terms of the metal cofactor required for catalysis. In this article we explore the role of the divalent metal ion in the mechanism of the 8-17 DNAzyme as a general acid, by measuring the influence of pH over the activity of a slower variant of the enzyme in the presence of Pb2+. We replaced G14, which has been identified as a general base in the mechanism of the enzyme, by the unnatural analog 2-aminopurine, with a lower pKa value of the N1 group. With this approach, we obtained a bell-shaped pH-rate profile with experimental pKa values of 5.4 and 7.0. Comparing these results with previous pH-rate profiles in the presence of Mg2+, our findings suggest the stabilization of the 5'-O leaving group by the hydrated metal ion acting as a general acid, in addition to the activation of the 2'-OH nucleophile by the general base G14.
Collapse
|
5
|
Moon WJ, Huang PJJ, Liu J. Probing Metal-Dependent Phosphate Binding for the Catalysis of the 17E DNAzyme. Biochemistry 2021; 60:1909-1918. [PMID: 34106684 DOI: 10.1021/acs.biochem.1c00091] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The RNA-cleaving 17E DNAzyme exhibits different levels of cleavage activity in the presence of various divalent metal ions, with Pb2+ giving the fastest cleavage. In this study, the metal-phosphate interaction is probed to understand the trend of activity with different metal ions. For the first-row transition metals, the lowest activity shown by Ni2+ correlates with the inhibition by the inorganic phosphate and its water ligand exchange rate, suggesting inner-sphere metal coordination. Cleavage activity with the two stereoisomers of the phosphorothioate-modified substrates, Rp and Sp, indicated that Mg2+, Mn2+, Fe2+, and Co2+ had the highest Sp:Rp activity ratio of >900. Comparatively, the activity was much less affected using the thiophilic metals, including Pb2+, suggesting inner-sphere coordination. The pH-rate profiles showed that Pb2+ was different than the rest of the metal ions in having a smaller slope and a similar fitted apparent pKa and the pKa of metal-bound water. Combining previous reports and our current results, we propose that Pb2+ most likely plays the role of a general acid while the other metal ions are Lewis acid catalysts interacting with the scissile phosphate.
Collapse
Affiliation(s)
- Woohyun J Moon
- Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Po-Jung Jimmy Huang
- Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Juewen Liu
- Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| |
Collapse
|
6
|
Cepeda-Plaza M, Peracchi A. Insights into DNA catalysis from structural and functional studies of the 8-17 DNAzyme. Org Biomol Chem 2020; 18:1697-1709. [DOI: 10.1039/c9ob02453k] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The review examines functional knowledge gathered over two decades of research on the 8-17 DNAzyme, focusing on three aspects: the structural requirements for catalysis, the role of metal ions and the participation of general acid-base catalysis.
Collapse
Affiliation(s)
| | - Alessio Peracchi
- Department of Chemistry
- Life Sciences and Environmental Sustainability
- University of Parma
- Parma
- Italy
| |
Collapse
|
7
|
Du S, Li Y, Chai Z, Shi W, He J. Functionalization of 8-17 DNAzymes modulates catalytic efficiency and divalent metal ion preference. Bioorg Chem 2019; 94:103401. [PMID: 31711763 DOI: 10.1016/j.bioorg.2019.103401] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Revised: 10/17/2019] [Accepted: 10/24/2019] [Indexed: 11/26/2022]
Abstract
8-17 and 17E DNAzyme are being explored as biosensors for metal ions and RNA motifs of interest, more sensitive and efficient DNAzymes are required to meet the practical applications. Their similarity in the catalytic cores and differences in catalytic efficiency and metal ion dependence initiated great interest about the contribution of the catalytic residues. Functionalization of four adenine residues in the catalytic cores of 8-17 DNAzyme and 17E was conducted with amino, guanidinium, and imidazolyl groups. In the bulge loops of 8-17 and 17E, N6-(3-aminopropyl)-2'-deoxyadenosine (residue 1) at A15 led to new DNAzymes 8-17DZ-A15-1 and 17E-A15-1, with much more efficient cleavage ability in the Ca2+-mediated reaction and the greater preference for Ca2+ over Mg2+ than 8-17 DNAzyme and 17E, respectively, especially with a concentration-dependent increase of the selectivity, which is different from most DNAzymes with the similar dependence on both Mg2+ and Ca2+. With this kind of post-selection modification on 8-17 DNAzymes, for the first time, the catalytic efficiency and metal ion selectivity could be positively modulated. It is also helpful for the catalyic mechanistic studies of these DNAzymes, especially, the role of the unconserved A15 should be emphasized.
Collapse
Affiliation(s)
- Shanshan Du
- State Key Laboratory of Toxicology and Medical Countermeasures, Beijing Institute of Pharmacology and Toxicology, Beijing 100850, China
| | - Yang Li
- State Key Laboratory of Toxicology and Medical Countermeasures, Beijing Institute of Pharmacology and Toxicology, Beijing 100850, China
| | - Zhilong Chai
- School of Pharmaceutical Sciences, Guizhou University, Guizhou 550025, China
| | - Weiguo Shi
- State Key Laboratory of Toxicology and Medical Countermeasures, Beijing Institute of Pharmacology and Toxicology, Beijing 100850, China.
| | - Junlin He
- State Key Laboratory of Toxicology and Medical Countermeasures, Beijing Institute of Pharmacology and Toxicology, Beijing 100850, China.
| |
Collapse
|