1
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Clement PC, Sapam T, Nair DT. A conserved polar residue plays a critical role in mismatch detection in A-family DNA polymerases. Int J Biol Macromol 2024:131965. [PMID: 38697428 DOI: 10.1016/j.ijbiomac.2024.131965] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Revised: 04/26/2024] [Accepted: 04/27/2024] [Indexed: 05/05/2024]
Abstract
In A-family DNA polymerases (dPols), a functional 3'-5' exonuclease activity is known to proofread newly synthesized DNA. The identification of a mismatch in substrate DNA leads to transfer of the primer strand from the polymerase active site to the exonuclease active site. To shed more light regarding the mechanism responsible for the detection of mismatches, we have utilized DNA polymerase 1 from Aquifex pyrophilus (ApPol1). The enzyme synthesized DNA with high fidelity and exhibited maximal exonuclease activity with DNA substrates bearing mismatches at the -2 and - 3 positions. The crystal structure of apo-ApPol1 was utilized to generate a computational model of the functional ternary complex of this enzyme. The analysis of the model showed that N332 forms interactions with minor groove atoms of the base pairs at the -2 and - 3 positions. The majority of known A-family dPols show the presence of Asn at a position equivalent to N332. The N332L mutation led to a decrease in the exonuclease activity for representative purine-pyrimidine, and pyrimidine-pyrimidine mismatches at -2 and - 3 positions, respectively. Overall, our findings suggest that conserved polar residues located towards the minor groove may facilitate the detection of position-specific mismatches to enhance the fidelity of DNA synthesis.
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Affiliation(s)
- Patterson C Clement
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad 121 001, Haryana (NCR Delhi), India
| | - Tuleshwori Sapam
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad 121 001, Haryana (NCR Delhi), India
| | - Deepak T Nair
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad 121 001, Haryana (NCR Delhi), India.
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2
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Ganesan VV, Nair DT, Bhatt P, Sturla SJ, Serrano JF. Call for Papers for Special Issue Advancing Science in India: Chemistry and Toxicology. Chem Res Toxicol 2023; 36:1829. [PMID: 38105684 DOI: 10.1021/acs.chemrestox.3c00356] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2023]
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3
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Jaiswal D, Verma S, Nair DT, Salunke DM. Antibody multispecificity: A necessary evil? Mol Immunol 2022; 152:153-161. [DOI: 10.1016/j.molimm.2022.10.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Revised: 10/20/2022] [Accepted: 10/24/2022] [Indexed: 11/09/2022]
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4
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Parray HA, Narayanan N, Garg S, Rizvi ZA, Shrivastava T, Kushwaha S, Singh J, Murugavelu P, Anantharaj A, Mehdi F, Raj N, Singh S, Dandotiya J, Lukose A, Jamwal D, Kumar S, Chiranjivi AK, Dhyani S, Mishra N, Kumar S, Jakhar K, Sonar S, Panchal AK, Tripathy MR, Chowdhury SR, Ahmed S, Samal S, Mani S, Bhattacharyya S, Das S, Sinha S, Luthra K, Batra G, Sehgal D, Medigeshi GR, Sharma C, Awasthi A, Garg PK, Nair DT, Kumar R. A broadly neutralizing monoclonal antibody overcomes the mutational landscape of emerging SARS-CoV-2 variants of concern. PLoS Pathog 2022; 18:e1010994. [PMID: 36508467 PMCID: PMC9779650 DOI: 10.1371/journal.ppat.1010994] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Revised: 12/22/2022] [Accepted: 11/08/2022] [Indexed: 12/14/2022] Open
Abstract
The emergence of new variants of SARS-CoV-2 necessitates unremitting efforts to discover novel therapeutic monoclonal antibodies (mAbs). Here, we report an extremely potent mAb named P4A2 that can neutralize all the circulating variants of concern (VOCs) with high efficiency, including the highly transmissible Omicron. The crystal structure of the P4A2 Fab:RBD complex revealed that the residues of the RBD that interact with P4A2 are a part of the ACE2-receptor-binding motif and are not mutated in any of the VOCs. The pan coronavirus pseudotyped neutralization assay confirmed that the P4A2 mAb is specific for SARS-CoV-2 and its VOCs. Passive administration of P4A2 to K18-hACE2 transgenic mice conferred protection, both prophylactically and therapeutically, against challenge with VOCs. Overall, our data shows that, the P4A2 mAb has immense therapeutic potential to neutralize the current circulating VOCs. Due to the overlap between the P4A2 epitope and ACE2 binding site on spike-RBD, P4A2 may also be highly effective against a number of future variants.
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Affiliation(s)
- Hilal Ahmad Parray
- Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Naveen Narayanan
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Sonal Garg
- Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Zaigham Abbas Rizvi
- Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Tripti Shrivastava
- Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Sachin Kushwaha
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, India
| | - Janmejay Singh
- Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Praveenkumar Murugavelu
- Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Anbalagan Anantharaj
- Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Farha Mehdi
- Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Nisha Raj
- Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Shivam Singh
- Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Jyotsna Dandotiya
- Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Asha Lukose
- Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Deepti Jamwal
- Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Sandeep Kumar
- Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Adarsh K. Chiranjivi
- Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Samridhi Dhyani
- Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Nitesh Mishra
- Department of Biochemistry, All India Institute of Medical Sciences, New Delhi, India
| | - Sanjeev Kumar
- ICGEB-Emory Vaccine Center, International Centre for Genetic Engineering and Biotechnology, New Delhi, India
| | - Kamini Jakhar
- Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Sudipta Sonar
- Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Anil Kumar Panchal
- Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Manas Ranjan Tripathy
- Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Shirlie Roy Chowdhury
- Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Shubbir Ahmed
- Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Sweety Samal
- Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Shailendra Mani
- Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Sankar Bhattacharyya
- Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Supratik Das
- Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Subrata Sinha
- Department of Biochemistry, All India Institute of Medical Sciences, New Delhi, India
| | - Kalpana Luthra
- Department of Biochemistry, All India Institute of Medical Sciences, New Delhi, India
| | - Gaurav Batra
- Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Devinder Sehgal
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, India
| | - Guruprasad R. Medigeshi
- Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Chandresh Sharma
- Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Amit Awasthi
- Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Pramod Kumar Garg
- Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Deepak T. Nair
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad, Haryana, India
| | - Rajesh Kumar
- Translational Health Science and Technology Institute, NCR Biotech Science Cluster, Faridabad, Haryana, India
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Sharma M, Nair DT. Pfprex from
Plasmodium falciparum
can bypass oxidative stress‐induced DNA lesions. FEBS J 2022; 289:5218-5240. [DOI: 10.1111/febs.16414] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Revised: 01/13/2022] [Accepted: 02/25/2022] [Indexed: 12/24/2022]
Affiliation(s)
- Minakshi Sharma
- Regional Centre for Biotechnology Faridabad India
- Kalinga Institute of Industrial Technology Bhubaneshwar India
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6
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Bhatia S, Narayanan N, Nagpal S, Nair DT. Antiviral therapeutics directed against RNA dependent RNA polymerases from positive-sense viruses. Mol Aspects Med 2021; 81:101005. [PMID: 34311994 DOI: 10.1016/j.mam.2021.101005] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Revised: 07/14/2021] [Accepted: 07/16/2021] [Indexed: 01/18/2023]
Abstract
Viruses with positive-sense single stranded RNA (+ssRNA) genomes are responsible for different diseases and represent a global health problem. In addition to developing new vaccines that protect against severe illness on infection, it is imperative to identify new antiviral molecules to treat infected patients. The genome of these RNA viruses generally codes for an enzyme with RNA dependent RNA polymerase (RdRP) activity. This molecule is centrally involved in the duplication of the RNA genome. Inhibition of this enzyme by small molecules will prevent duplication of the RNA genome and thus reduce the viral titer. An overview of the different therapeutic strategies used to inhibit RdRPs from +ssRNA viruses is provided, along with an analysis of these enzymes to highlight new binding sites for inhibitors.
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Affiliation(s)
- Sonam Bhatia
- Regional Centre for Biotechnology, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad, 121001, India
| | - Naveen Narayanan
- Regional Centre for Biotechnology, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad, 121001, India
| | - Shilpi Nagpal
- Regional Centre for Biotechnology, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad, 121001, India; National Centre for Biological Sciences, Tata Institute of Fundamental Research, GKVK Campus, Bangalore, 560065, India
| | - Deepak T Nair
- Regional Centre for Biotechnology, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad, 121001, India.
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7
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Narayanan N, Nair DT. Ritonavir may inhibit exoribonuclease activity of nsp14 from the SARS-CoV-2 virus and potentiate the activity of chain terminating drugs. Int J Biol Macromol 2020; 168:272-278. [PMID: 33309661 PMCID: PMC7724963 DOI: 10.1016/j.ijbiomac.2020.12.038] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Revised: 12/05/2020] [Accepted: 12/05/2020] [Indexed: 01/18/2023]
Abstract
SARS-CoV-2is the causative agent for the ongoing COVID19 pandemic, and this virus belongs to the Coronaviridae family. The nsp14 protein of SARS-CoV-2 houses a 3' to 5' exoribonuclease activity responsible for removing mismatches that arise during genome duplication. A homology model of nsp10-nsp14 complex was used to carry out in silico screening to identify molecules among natural products, or FDA approved drugs that can potentially inhibit the activity of nsp14. This exercise showed that ritonavir might bind to the exoribonuclease active site of the nsp14 protein. A model of the SARS-CoV-2-nsp10-nsp14 complex bound to substrate RNA showed that the ritonavir binding site overlaps with that of the 3' nucleotide of substrate RNA. A comparison of the calculated energies of binding for RNA and ritonavir suggested that the drug may bind to the active site of nsp14 with significant affinity. It is, therefore, possible that ritonavir may prevent association with substrate RNA and thus inhibit the exoribonuclease activity of nsp14. Overall, our computational studies suggest that ritonavir may serve as an effective inhibitor of the nsp14 protein. nsp14 is known to attenuate the inhibitory effect of drugs that function through premature termination of viral genome replication. Hence, ritonavir may potentiate the therapeutic properties of drugs such as remdesivir, favipiravir and ribavirin.
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Affiliation(s)
- Naveen Narayanan
- Laboratory of Genomic Integrity and Evolution, Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad 121001, Haryana, India; Manipal Academy of Higher Education, Manipal 576104, Karnataka, India
| | - Deepak T Nair
- Laboratory of Genomic Integrity and Evolution, Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad 121001, Haryana, India.
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8
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Narayanan N, Nair DT. Vitamin B12 may inhibit RNA-dependent-RNA polymerase activity of nsp12 from the SARS-CoV-2 virus. IUBMB Life 2020; 72:2112-2120. [PMID: 32812340 PMCID: PMC7461454 DOI: 10.1002/iub.2359] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2020] [Revised: 06/30/2020] [Accepted: 07/02/2020] [Indexed: 01/18/2023]
Abstract
SARS‐CoV‐2 is the causative agent for the ongoing COVID19 pandemic, and this virus belongs to the Coronaviridae family. Like other members of this family, the virus possesses a positive‐sense single‐stranded RNA genome. The genome encodes for the nsp12 protein, which houses the RNA‐dependent‐RNA polymerase (RdRP) activity responsible for the replication of the viral genome. A homology model of nsp12 was prepared using the structure of the SARS nsp12 (6NUR) as a model. The model was used to carry out in silico screening to identify molecules among natural products, or Food and Drug Administration‐approved drugs that can potentially inhibit the activity of nsp12. This exercise showed that vitamin B12 (methylcobalamin) may bind to the active site of the nsp12 protein. A model of the nsp12 in complex with substrate RNA and incoming NTP showed that vitamin B12 binding site overlaps with that of the incoming nucleotide. A comparison of the calculated energies of binding for RNA plus NTP and methylcobalamin suggested that the vitamin may bind to the active site of nsp12 with significant affinity. It is, therefore, possible that methylcobalamin binding may prevent association with RNA and NTP and thus inhibit the RdRP activity of nsp12. Overall, our computational studies suggest that methylcobalamin form of vitamin B12 may serve as an effective inhibitor of the nsp12 protein.
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Affiliation(s)
- Naveen Narayanan
- Laboratory of Genomic Integrity and Evolution, Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad, India.,Manipal Academy of Higher Education, Manipal, India
| | - Deepak T Nair
- Laboratory of Genomic Integrity and Evolution, Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad, India
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9
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Johnson MK, Kottur J, Nair DT. A polar filter in DNA polymerases prevents ribonucleotide incorporation. Nucleic Acids Res 2020; 47:10693-10705. [PMID: 31544946 PMCID: PMC6846668 DOI: 10.1093/nar/gkz792] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Revised: 09/02/2019] [Accepted: 09/09/2019] [Indexed: 12/17/2022] Open
Abstract
The presence of ribonucleotides in DNA can lead to genomic instability and cellular lethality. To prevent adventitious rNTP incorporation, the majority of the DNA polymerases (dPols) possess a steric filter. The dPol named MsDpo4 (Mycobacterium smegmatis) naturally lacks this steric filter and hence is capable of rNTP addition. The introduction of the steric filter in MsDpo4 did not result in complete abrogation of the ability of this enzyme to incorporate ribonucleotides. In comparison, DNA polymerase IV (PolIV) from Escherichia coli exhibited stringent selection for deoxyribonucleotides. A comparison of MsDpo4 and PolIV led to the discovery of an additional polar filter responsible for sugar selectivity. Thr43 represents the filter in PolIV and this residue forms interactions with the incoming nucleotide to draw it closer to the enzyme surface. As a result, the 2’-OH in rNTPs will clash with the enzyme surface, and therefore ribonucleotides cannot be accommodated in the active site in a conformation compatible with productive catalysis. The substitution of the equivalent residue in MsDpo4–Cys47, with Thr led to a drastic reduction in the ability of the mycobacterial enzyme to incorporate rNTPs. Overall, our studies evince that the polar filter serves to prevent ribonucleotide incorporation by dPols.
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Affiliation(s)
- Mary K Johnson
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad 121001, India.,National Centre for Biological Sciences, Tata Institute of Fundamental Research, GKVK Campus, Bangalore 560065, India
| | - Jithesh Kottur
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad 121001, India
| | - Deepak T Nair
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad 121001, India
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10
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Jain A, Kumar A, Shikhi M, Kumar A, Nair DT, Salunke DM. The structure of MP-4 from Mucuna pruriens at 2.22 Å resolution. Acta Crystallogr F Struct Biol Commun 2020; 76:47-57. [PMID: 32039885 PMCID: PMC7010354 DOI: 10.1107/s2053230x20000199] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Accepted: 01/08/2020] [Indexed: 11/10/2022] Open
Abstract
The structure of the MP-4 protein was previously determined at a resolution of 2.8 Å. Owing to the unavailability of gene-sequence information at the time, the side-chain assignment was carried out on the basis of a partial sequence available through Edman degradation, sequence homology to orthologs and electron density. The structure of MP-4 has now been determined at a higher resolution (2.22 Å) in another space group and all of the structural inferences that were presented in the previous report of the structure were validated. In addition, the present data allowed an improved assignment of side chains and enabled further analysis of the MP-4 structure, and the accuracy of the assignment was confirmed by the recently available gene sequence. The study reinforces the traditional concept that conservative interpretations of relatively low-resolution structures remain correct even with the availability of high-resolution data.
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Affiliation(s)
- Abha Jain
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone, Faridabad–Gurgaon Expressway, Faridabad 121 001, India
| | - Amit Kumar
- International Centre for Genetic Engineering and Biotechnology (ICGEB), Aruna Asaf Ali Marg, New Delhi 110 067, India
| | - Meha Shikhi
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone, Faridabad–Gurgaon Expressway, Faridabad 121 001, India
- Kalinga Institute of Industrial Technology, Bhubaneswar, Odisha 751 024, India
| | - Ashish Kumar
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone, Faridabad–Gurgaon Expressway, Faridabad 121 001, India
| | - Deepak T. Nair
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone, Faridabad–Gurgaon Expressway, Faridabad 121 001, India
| | - Dinakar M. Salunke
- International Centre for Genetic Engineering and Biotechnology (ICGEB), Aruna Asaf Ali Marg, New Delhi 110 067, India
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Narayanan N, Banerjee A, Jain D, Kulkarni DS, Sharma R, Nirwal S, Rao DN, Nair DT. Tetramerization at Low pH Licenses DNA Methylation Activity of M.HpyAXI in the Presence of Acid Stress. J Mol Biol 2020; 432:324-342. [DOI: 10.1016/j.jmb.2019.10.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2019] [Revised: 10/01/2019] [Accepted: 10/01/2019] [Indexed: 11/25/2022]
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12
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Kottur J, Nair DT. Pyrophosphate hydrolysis is an intrinsic and critical step of the DNA synthesis reaction. Nucleic Acids Res 2019; 46:5875-5885. [PMID: 29850882 PMCID: PMC6159520 DOI: 10.1093/nar/gky402] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Accepted: 05/15/2018] [Indexed: 11/14/2022] Open
Abstract
DNA synthesis by DNA polymerases (dPols) is central to duplication and maintenance of the genome in all living organisms. dPols catalyze the formation of a phosphodiester bond between the incoming deoxynucleoside triphosphate and the terminal primer nucleotide with the release of a pyrophosphate (PPi) group. It is believed that formation of the phosphodiester bond is an endergonic reaction and PPi has to be hydrolyzed by accompanying pyrophosphatase enzymes to ensure that the free energy change of the DNA synthesis reaction is negative and it can proceed in the forward direction. The fact that DNA synthesis proceeds in vitro in the absence of pyrophosphatases represents a long-standing conundrum regarding the thermodynamics of the DNA synthesis reaction. Using time-resolved crystallography, we show that hydrolysis of PPi is an intrinsic and critical step of the DNA synthesis reaction catalyzed by dPols. The hydrolysis of PPi occurs after the formation of the phosphodiester bond and ensures that the DNA synthesis reaction is energetically favorable without the need for additional enzymes. Also, we observe that DNA synthesis is a two Mg2+ ion assisted stepwise associative SN2 reaction. Overall, this study provides deep temporal insight regarding the primary enzymatic reaction responsible for genome duplication.
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Affiliation(s)
- Jithesh Kottur
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad 121 001, India
| | - Deepak T Nair
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad 121 001, India
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Nirwal S, Kulkarni DS, Sharma A, Rao DN, Nair DT. Mechanism of formation of a toroid around DNA by the mismatch sensor protein. Nucleic Acids Res 2019; 46:256-266. [PMID: 29182773 PMCID: PMC5758902 DOI: 10.1093/nar/gkx1149] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Accepted: 11/01/2017] [Indexed: 01/26/2023] Open
Abstract
The DNA mismatch repair (MMR) pathway removes errors that appear during genome replication. MutS is the primary mismatch sensor and forms an asymmetric dimer that encircles DNA to bend it to scan for mismatches. The mechanism utilized to load DNA into the central tunnel was unknown and the origin of the force required to bend DNA was unclear. We show that, in absence of DNA, MutS forms a symmetric dimer wherein a gap exists between the monomers through which DNA can enter the central tunnel. The comparison with structures of MutS-DNA complexes suggests that the mismatch scanning monomer (Bm) will move by nearly 50 Å to associate with the other monomer (Am). Consequently, the N-terminal domains of both monomers will press onto DNA to bend it. The proposed mechanism of toroid formation evinces that the force required to bend DNA arises primarily due to the movement of Bm and hence, the MutS dimer acts like a pair of pliers to bend DNA. We also shed light on the allosteric mechanism that influences the expulsion of adenosine triphosphate from Am on DNA binding. Overall, this study provides mechanistic insight regarding the primary event in MMR i.e. the assembly of the MutS-DNA complex.
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Affiliation(s)
- Shivlee Nirwal
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad, 121001, Haryana, India.,Manipal University, Manipal, 576104, Karnataka, India
| | - Dhananjaya S Kulkarni
- Department of Biochemistry, Indian Institute of Science, Bangalore, 560012, Karnataka, India
| | - Amit Sharma
- TERI-DIAKEN Nanobiotechnolgy Centre, TERI-Gram, Gual Pahari, Gurgaon-Faridabad Road, Gurgaon, 122001, Haryana, India
| | - Desirazu N Rao
- Department of Biochemistry, Indian Institute of Science, Bangalore, 560012, Karnataka, India
| | - Deepak T Nair
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad, 121001, Haryana, India
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Ghodke PP, Bommisetti P, Nair DT, Pradeepkumar PI. Synthesis of N 2-Deoxyguanosine Modified DNAs and the Studies on Their Translesion Synthesis by the E. coli DNA Polymerase IV. J Org Chem 2019; 84:1734-1747. [PMID: 30628447 DOI: 10.1021/acs.joc.8b02082] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
We report the synthesis of N2-aryl (benzyl, naphthyl, anthracenyl, and pyrenyl)-deoxyguanosine (dG) modified phosphoramidite building blocks and the corresponding damaged DNAs. Primer extension studies using E. coli Pol IV, a translesion polymerase, demonstrate that translesion synthesis (TLS) across these N2-dG adducts is error free. However, the efficiency of TLS activity decreases with increase in the steric bulkiness of the adducts. Molecular dynamics simulations of damaged DNA-Pol IV complexes reveal the van der Waals interactions between key amino acid residues (Phe13, Ile31, Gly32, Gly33, Ser42, Pro73, Gly74, Phe76, and Tyr79) of the enzyme and adduct that help to accommodate the bulky damages in a hydrophobic pocket to facilitate TLS. Overall, the results presented here provide insights into the TLS across N2-aryl-dG damaged DNAs by Pol IV.
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Affiliation(s)
- Pratibha P Ghodke
- Department of Chemistry , Indian Institute of Technology Bombay , Mumbai 400076 , India
| | - Praneeth Bommisetti
- Department of Chemistry , Indian Institute of Technology Bombay , Mumbai 400076 , India
| | - Deepak T Nair
- Regional Centre for Biotechnology , NCR Biotech Science Cluster , third Milestone, Faridabad-Gurgaon Expressway , Faridabad 121001 , India
| | - P I Pradeepkumar
- Department of Chemistry , Indian Institute of Technology Bombay , Mumbai 400076 , India
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15
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Kumar A, Gupta C, Nair DT, Salunke DM. MP-4 contributes to snake venom neutralization by Mucuna pruriens seeds through an indirect antibody-mediated mechanism. J Biol Chem 2018; 293:11253. [DOI: 10.1074/jbc.ec118.001735] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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16
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Sharma R, Nirwal S, Narayanan N, Nair DT. Dimerization through the RING-Finger Domain Attenuates Excision Activity of the piggyBac Transposase. Biochemistry 2018; 57:2913-2922. [DOI: 10.1021/acs.biochem.7b01191] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Rahul Sharma
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad 121001, Haryana, India
- Manipal Academy of Higher Education, Manipal 576104, Karnataka, India
| | - Shivlee Nirwal
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad 121001, Haryana, India
- Manipal Academy of Higher Education, Manipal 576104, Karnataka, India
| | - Naveen Narayanan
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad 121001, Haryana, India
- Manipal Academy of Higher Education, Manipal 576104, Karnataka, India
| | - Deepak T. Nair
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad 121001, Haryana, India
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17
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Salunke DM, Nair DT. Macromolecular structures: Quality assessment and biological interpretation. IUBMB Life 2017; 69:563-571. [DOI: 10.1002/iub.1640] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Accepted: 04/25/2017] [Indexed: 02/05/2023]
Affiliation(s)
- Dinakar M. Salunke
- International Centre for Genetic Engineering and Biotechnology; Aruna Asaf Ali Marg; New Delhi India
| | - Deepak T. Nair
- Regional Centre for Biotechnology, NCR Biotech Science Cluster; 3rd Milestone, Faridabad-Gurgaon Expressway Faridabad Haryana India
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18
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Kumar A, Gupta C, Nair DT, Salunke DM. MP-4 Contributes to Snake Venom Neutralization by Mucuna pruriens Seeds through an Indirect Antibody-mediated Mechanism. J Biol Chem 2016; 291:11373-84. [PMID: 26987900 DOI: 10.1074/jbc.m115.699173] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Indexed: 11/06/2022] Open
Abstract
Mortality due to snakebite is a serious public health problem, and available therapeutics are known to induce debilitating side effects. Traditional medicine suggests that seeds of Mucuna pruriens can provide protection against the effects of snakebite. Our aim is to identify the protein(s) that may be important for snake venom neutralization and elucidate its mechanism of action. To this end, we have identified and purified a protein from M. pruriens, which we have named MP-4. The full-length polypeptide sequence of MP-4 was obtained through N-terminal sequencing of peptide fragments. Sequence analysis suggested that the protein may belong to the Kunitz-type protease inhibitor family and therefore may potentially neutralize the proteases present in snake venom. Using various structural and biochemical tools coupled with in vivo assays, we are able to show that MP-4 does not afford direct protection against snake venom because it is actually a poor inhibitor of serine proteases. Further experiments showed that antibodies generated against MP-4 cross-react with the whole venom and provide protection to mice against Echis carinatus snake venom. This study shows that the MP-4 contributes significantly to the snake venom neutralization activity of M. pruriens seeds through an indirect antibody-mediated mechanism.
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Affiliation(s)
- Ashish Kumar
- From the Structural Biology Unit, National Institute of Immunology, Aruna Asaf Ali Road, New Delhi 110 067, India, the Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad 121 001, India, and
| | - Chitra Gupta
- From the Structural Biology Unit, National Institute of Immunology, Aruna Asaf Ali Road, New Delhi 110 067, India
| | - Deepak T Nair
- the Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad 121 001, India, and
| | - Dinakar M Salunke
- From the Structural Biology Unit, National Institute of Immunology, Aruna Asaf Ali Road, New Delhi 110 067, India, the Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad 121 001, India, and the International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110 067, India
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19
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Kottur J, Nair DT. Reactive Oxygen Species Play an Important Role in the Bactericidal Activity of Quinolone Antibiotics. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201509340] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Jithesh Kottur
- Regional Centre for Biotechnology; NCR Biotech Science Cluster; 3rd Milestone, Faridabad-Gurgaon Expressway Faridabad 121001 India
- Manipal University, Madhav Nagar; Manipal 576104 India
| | - Deepak T. Nair
- Regional Centre for Biotechnology; NCR Biotech Science Cluster; 3rd Milestone, Faridabad-Gurgaon Expressway Faridabad 121001 India
- National Centre for Biological Sciences, NCBS-TIFR, GKVK Campus; Bangalore 560065 India
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20
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Kottur J, Nair DT. Reactive Oxygen Species Play an Important Role in the Bactericidal Activity of Quinolone Antibiotics. Angew Chem Int Ed Engl 2016; 55:2397-400. [PMID: 26757158 DOI: 10.1002/anie.201509340] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Revised: 11/23/2015] [Indexed: 11/10/2022]
Abstract
Recent studies posit that reactive oxygen species (ROS) contribute to the cell lethality of bactericidal antibiotics. However, this conjecture has been challenged and remains controversial. To resolve this controversy, we adopted a strategy that involves DNA polymerase IV (PolIV). The nucleotide pool of the cell gets oxidized by ROS and PolIV incorporates the damaged nucleotides (especially 8oxodGTP) into the genome, which results in death of the bacteria. By using a combination of structural and biochemical tools coupled with growth assays, it was shown that selective perturbation of the 8oxodGTP incorporation activity of PolIV results in considerable enhancement of the survival of bacteria in the presence of the norfloxacin antibiotic. Our studies therefore indicate that ROS induced in bacteria by the presence of antibiotics in the environment contribute significantly to cell lethality.
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Affiliation(s)
- Jithesh Kottur
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad, 121001, India.,Manipal University, Madhav Nagar, Manipal, 576104, India
| | - Deepak T Nair
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad, 121001, India. .,National Centre for Biological Sciences, NCBS-TIFR, GKVK Campus, Bangalore, 560065, India.
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21
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Ghodke PP, Gore KR, Harikrishna S, Samanta B, Kottur J, Nair DT, Pradeepkumar PI. The N(2)-Furfuryl-deoxyguanosine Adduct Does Not Alter the Structure of B-DNA. J Org Chem 2016; 81:502-11. [PMID: 26650891 DOI: 10.1021/acs.joc.5b02341] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
N(2)-Furfuryl-deoxyguanosine (fdG) is carcinogenic DNA adduct that originates from furfuryl alcohol. It is also a stable structural mimic of the damage induced by the nitrofurazone family of antibiotics. For the structural and functional studies of this model N(2)-dG adduct, reliable and rapid access to fdG-modified DNAs are warranted. Toward this end, here we report the synthesis of fdG-modified DNAs using phosphoramidite chemistry involving only three steps. The functional integrity of the modified DNA has been verified by primer extension studies with DNA polymerases I and IV from E. coli. Introduction of fdG into a DNA duplex decreases the Tm by ∼1.6 °C/modification. Molecular dynamics simulations of a DNA duplex bearing the fdG adduct revealed that though the overall B-DNA structure is maintained, this lesion can disrupt W-C H-bonding, stacking interactions, and minor groove hydrations to some extent at the modified site, and these effects lead to slight variations in the local base pair parameters. Overall, our studies show that fdG is tolerated at the minor groove of the DNA to a better extent compared with other bulky DNA damages, and this property will make it difficult for the DNA repair pathways to detect this adduct.
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Affiliation(s)
- Pratibha P Ghodke
- Department of Chemistry, Indian Institute of Technology Bombay , Mumbai-400076, India
| | - Kiran R Gore
- Department of Chemistry, Indian Institute of Technology Bombay , Mumbai-400076, India.,Department of Chemistry, University of Mumbai , Mumbai-400098, India
| | - S Harikrishna
- Department of Chemistry, Indian Institute of Technology Bombay , Mumbai-400076, India
| | - Biswajit Samanta
- Department of Chemistry, Indian Institute of Technology Bombay , Mumbai-400076, India
| | - Jithesh Kottur
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, Third Milestone, Faridabad-Gurgaon Expressway, Faridabad-121001, India.,Manipal University, Manipal-576104, India
| | - Deepak T Nair
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, Third Milestone, Faridabad-Gurgaon Expressway, Faridabad-121001, India.,National Centre for Biological Sciences (NCBS-TIFR), GKVK Campus, Bellary Road, Bangalore-560065, India
| | - P I Pradeepkumar
- Department of Chemistry, Indian Institute of Technology Bombay , Mumbai-400076, India
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22
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Jain D, Narayanan N, Nair DT. Plasticity in Repressor-DNA Interactions Neutralizes Loss of Symmetry in Bipartite Operators. J Biol Chem 2015; 291:1235-42. [PMID: 26511320 DOI: 10.1074/jbc.m115.689695] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Indexed: 11/06/2022] Open
Abstract
Transcription factor-DNA interactions are central to gene regulation. Many transcription factors regulate multiple target genes and can bind sequences that do not conform strictly to the consensus. To understand the structural mechanism utilized by the transcription regulators to bind diverse target sequences, we have employed the repressor AraR from Bacillus subtilis as a model system. AraR is known to bind to eight different operator sites in the bacterial genome. Although there are differences in the sequences of four of these operators, ORE1, ORX1, ORA1, and ORR3, the AraR-DNA binding domain (AraR-DBD) as well as full-length AraR unexpectedly binds to each of these sequences with similar affinities as measured by fluorescence anisotropy experiments. We have determined crystal structures of AraR-DBD in complex with two different natural operators ORE1 and ORX1 up to 2.07 and 1.97 Å resolution, respectively. These structures were compared with the previously reported structures of AraR-DBD bound to two other natural operators (ORA1 and ORR3). Interactions of two molecules of AraR-DBD with the symmetric operator, ORE1, are identical, but their interaction with the non-symmetric operator ORX1 results in breakdown of the symmetry in protein-DNA interactions. The novel interactions observed are accompanied by local conformational change in the DNA. ChIP-sequencing (ChIP-Seq) data on other transcription factors has shown that they can bind to diverse targets, and hence the plasticity exhibited by AraR may be a general phenomenon. The ability of transcription factors to form alternate interactions may be important for employment in new functions and evolution of novel regulatory circuits.
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Affiliation(s)
- Deepti Jain
- From the Transcription Regulation Lab and the National Centre for Biological Sciences (NCBS-TIFR), UAS-GKVK Campus, Bellary Road, Bangalore 560065, and
| | - Naveen Narayanan
- the National Centre for Biological Sciences (NCBS-TIFR), UAS-GKVK Campus, Bellary Road, Bangalore 560065, and the Genomic Integrity and Plasticity Lab, Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone, Faridabad-Gurgaon Expressway, Bhankri Village, Faridabad 121001, Manipal University, Manipal, 576104 Karnataka, India
| | - Deepak T Nair
- the National Centre for Biological Sciences (NCBS-TIFR), UAS-GKVK Campus, Bellary Road, Bangalore 560065, and the Genomic Integrity and Plasticity Lab, Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone, Faridabad-Gurgaon Expressway, Bhankri Village, Faridabad 121001
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23
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Nair DT, Kottur J, Sharma R. A rescue act: Translesion DNA synthesis past N(2) -deoxyguanosine adducts. IUBMB Life 2015; 67:564-74. [PMID: 26173005 DOI: 10.1002/iub.1403] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Accepted: 06/17/2015] [Indexed: 01/14/2023]
Abstract
Genomic DNA is continually subjected to a number of chemical insults that result in the formation of modified nucleotides--termed as DNA lesions. The N(2) -atom of deoxyguanosine is particularly reactive and a number of chemicals react at this site to form different kinds of DNA adducts. The N(2) -deoxyguanosine adducts perturb different genomic processes and are particularly deleterious for DNA replication as they have a strong tendency to inhibit replicative DNA polymerases. Many organisms possess specialized dPols--generally classified in the Y-family--that serves to rescue replication stalled at N(2) -dG and other adducts. A review of minor groove N(2) -adducts and the known strategies utilized by Y-family dPols to replicate past these lesions will be presented here.
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Affiliation(s)
- Deepak T Nair
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad, Haryana, 121 001, India
| | - Jithesh Kottur
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad, Haryana, 121 001, India.,Manipal University, Manipal.Edu, Manipal, 576104, Karnataka, India
| | - Rahul Sharma
- Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad, Haryana, 121 001, India.,Manipal University, Manipal.Edu, Manipal, 576104, Karnataka, India
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24
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Weinert T, Olieric V, Waltersperger S, Panepucci E, Chen L, Zhang H, Zhou D, Rose J, Ebihara A, Kuramitsu S, Li D, Howe N, Schnapp G, Pautsch A, Bargsten K, Prota AE, Surana P, Kottur J, Nair DT, Basilico F, Cecatiello V, Pasqualato S, Boland A, Weichenrieder O, Wang BC, Steinmetz MO, Caffrey M, Wang M. Erratum: Corrigendum: Fast native-SAD phasing for routine macromolecular structure determination. Nat Methods 2015. [DOI: 10.1038/nmeth0715-692a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Kottur J, Sharma A, Gore KR, Narayanan N, Samanta B, Pradeepkumar PI, Nair DT. Unique structural features in DNA polymerase IV enable efficient bypass of the N2 adduct induced by the nitrofurazone antibiotic. Structure 2014; 23:56-67. [PMID: 25497730 DOI: 10.1016/j.str.2014.10.019] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Revised: 10/27/2014] [Accepted: 10/28/2014] [Indexed: 11/17/2022]
Abstract
The reduction in the efficacy of therapeutic antibiotics represents a global problem of increasing intensity and concern. Nitrofuran antibiotics act primarily through the formation of covalent adducts at the N(2) atom of the deoxyguanosine nucleotide in genomic DNA. These adducts inhibit replicative DNA polymerases (dPols), leading to the death of the prokaryote. N(2)-furfuryl-deoxyguanosine (fdG) represents a stable structural analog of the nitrofuran-induced adducts. Unlike other known dPols, DNA polymerase IV (PolIV) from E. coli can bypass the fdG adduct accurately with high catalytic efficiency. This property of PolIV is central to its role in reducing the sensitivity of E. coli toward nitrofuran antibiotics such as nitrofurazone (NFZ). We present the mechanism used by PolIV to bypass NFZ-induced adducts and thus improve viability of E. coli in the presence of NFZ. Our results can be used to develop specific inhibitors of PolIV that may potentiate the activity of nitrofuran antibiotics.
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Affiliation(s)
- Jithesh Kottur
- National Centre for Biological Sciences (NCBS-TIFR), GKVK Campus, Bellary Road, Bangalore 560065, India; Manipal University, Manipal.edu, Madhav Nagar, Manipal 576104, India
| | - Amit Sharma
- National Centre for Biological Sciences (NCBS-TIFR), GKVK Campus, Bellary Road, Bangalore 560065, India
| | - Kiran R Gore
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Naveen Narayanan
- National Centre for Biological Sciences (NCBS-TIFR), GKVK Campus, Bellary Road, Bangalore 560065, India; Manipal University, Manipal.edu, Madhav Nagar, Manipal 576104, India
| | - Biswajit Samanta
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | | | - Deepak T Nair
- Regional Centre for Biotechnology, 180, Udyog Vihar, Phase 1, Gurgaon 122016, India; National Centre for Biological Sciences (NCBS-TIFR), GKVK Campus, Bellary Road, Bangalore 560065, India.
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Surana P, Satchidanandam V, Nair DT. RNA-dependent RNA polymerase of Japanese encephalitis virus binds the initiator nucleotide GTP to form a mechanistically important pre-initiation state. Nucleic Acids Res 2014; 42:2758-73. [PMID: 24293643 PMCID: PMC3936712 DOI: 10.1093/nar/gkt1106] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Revised: 10/03/2013] [Accepted: 10/18/2013] [Indexed: 11/22/2022] Open
Abstract
Flaviviral RNA-dependent RNA polymerases (RdRps) initiate replication of the single-stranded RNA genome in the absence of a primer. The template sequence 5'-CU-3' at the 3'-end of the flaviviral genome is highly conserved. Surprisingly, flaviviral RdRps require high concentrations of the second incoming nucleotide GTP to catalyze de novo template-dependent RNA synthesis. We show that GTP stimulates de novo RNA synthesis by RdRp from Japanese encephalitis virus (jRdRp) also. Crystal structures of jRdRp complexed with GTP and ATP provide a basis for specific recognition of GTP. Comparison of the jRdRpGTP structure with other viral RdRp-GTP structures shows that GTP binds jRdRp in a novel conformation. Apo-jRdRp structure suggests that the conserved motif F of jRdRp occupies multiple conformations in absence of GTP. Motif F becomes ordered on GTP binding and occludes the nucleotide triphosphate entry tunnel. Mutational analysis of key residues that interact with GTP evinces that the jRdRpGTP structure represents a novel pre-initiation state. Also, binding studies show that GTP binding reduces affinity of RdRp for RNA, but the presence of the catalytic Mn(2+) ion abolishes this inhibition. Collectively, these observations suggest that the observed pre-initiation state may serve as a checkpoint to prevent erroneous template-independent RNA synthesis by jRdRp during initiation.
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Affiliation(s)
- Parag Surana
- National Centre for Biological Sciences (NCBS-TIFR), UAS-GKVK Campus, Bellary Road, Bangalore 560065, India and Department of Microbiology and Cell biology, Indian Institute of Science, Bangalore 560012, India
| | - Vijaya Satchidanandam
- National Centre for Biological Sciences (NCBS-TIFR), UAS-GKVK Campus, Bellary Road, Bangalore 560065, India and Department of Microbiology and Cell biology, Indian Institute of Science, Bangalore 560012, India
| | - Deepak T. Nair
- National Centre for Biological Sciences (NCBS-TIFR), UAS-GKVK Campus, Bellary Road, Bangalore 560065, India and Department of Microbiology and Cell biology, Indian Institute of Science, Bangalore 560012, India
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Sharma A, Kottur J, Narayanan N, Nair DT. A strategically located serine residue is critical for the mutator activity of DNA polymerase IV from Escherichia coli. Nucleic Acids Res 2013; 41:5104-14. [PMID: 23525461 PMCID: PMC3643571 DOI: 10.1093/nar/gkt146] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The Y-family DNA polymerase IV or PolIV (Escherichia coli) is the founding member of the DinB family and is known to play an important role in stress-induced mutagenesis. We have determined four crystal structures of this enzyme in its pre-catalytic state in complex with substrate DNA presenting the four possible template nucleotides that are paired with the corresponding incoming nucleotide triphosphates. In all four structures, the Ser42 residue in the active site forms interactions with the base moieties of the incipient Watson–Crick base pair. This residue is located close to the centre of the nascent base pair towards the minor groove. In vitro and in vivo assays show that the fidelity of the PolIV enzyme increases drastically when this Ser residue was mutated to Ala. In addition, the structure of PolIV with the mismatch A:C in the active site shows that the Ser42 residue plays an important role in stabilizing dCTP in a conformation compatible with catalysis. Overall, the structural, biochemical and functional data presented here show that the Ser42 residue is present at a strategic location to stabilize mismatches in the PolIV active site, and thus facilitate the appearance of transition and transversion mutations.
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Affiliation(s)
- Amit Sharma
- National Centre for Biological Sciences (NCBS-TIFR), UAS-GKVK Campus, Bellary Road, Bangalore 560065, India
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Abstract
Transcription factors modulate expression primarily through specific recognition of cognate sequences resident in the promoter region of target genes. AraR (Bacillus subtilis) is a repressor of genes involved in L-arabinose metabolism. It binds to eight different operators present in five different promoters with distinct affinities through a DNA binding domain at the N-terminus. The structures of AraR-NTD in complex with two distinct operators (ORA1 and ORR3) reveal that two monomers bind to one recognition motif (T/ANG) each in the bipartite operators. The structures show that the two recognition motifs are spaced apart by six bases in cases of ORA1 and eight bases in case of ORR3. This increase in the spacing in the operators by two base pairs results in a drastic change in the position and orientation of the second monomer on DNA in the case of ORR3 when compared with ORA1. Because AraR binds to the two operators with distinct affinities to achieve different levels of repression, this observation suggests that the variation in the spacing between core recognition motifs could be a strategy used by this transcription modulator to differentially influence gene expression.
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Affiliation(s)
| | - Deepak T. Nair
- *To whom correspondence should be addressed. Tel: +91 80 2366 6405; Fax: +91 80 2363 6662;
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29
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Sharma A, Subramanian V, Nair DT. The PAD region in the mycobacterial DinB homologue MsPolIV exhibits positional heterogeneity. Acta Crystallogr D Biol Crystallogr 2012; 68:960-7. [PMID: 22868761 DOI: 10.1107/s0907444912017623] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2012] [Accepted: 04/20/2012] [Indexed: 12/17/2022]
Abstract
Y-family DNA polymerases (dPols) have evolved to carry out translesion bypass to rescue stalled replication; prokaryotic members of this family also participate in the phenomenon of adaptive mutagenesis to relieve selection pressure imposed by a maladapted environment. In this study, the first structure of a member of this family from a prokaryote has been determined. The structure of MsPolIV, a Y-family dPol from Mycobacterium smegmatis, shows the presence of the characteristic finger, palm and thumb domains. Surprisingly, the electron-density map of the intact protein does not show density for the PAD region that is unique to members of this family. Analysis of the packing of the molecules in the crystals showed the existence of large solvent-filled voids in which the PAD region could be located in multiple conformations. In line with this observation, analytical gel-filtration and dynamic light-scattering studies showed that MsPolIV undergoes significant compaction upon DNA binding. The PAD region is known to insert into the major groove of the substrate DNA and to play a major role in shaping the active site. Comparison with structures of other Y-family dPols shows that in the absence of tertiary contacts between the PAD domain and the other domains this region has the freedom to adopt multiple orientations. This structural attribute of the PAD will allow these enzymes to accommodate the alterations in the width of the DNA double helix that are necessary to achieve translesion bypass and adaptive mutagenesis and will also allow regulation of their activity to prevent adventitious error-prone DNA synthesis.
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Affiliation(s)
- Amit Sharma
- National Centre for Biological Sciences (NCBS-TIFR), UAS-GKVK Campus, Bellary Road, Bangalore 560 065, India
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Sharma A, Nair DT. Cloning, expression, purification, crystallization and preliminary crystallographic analysis of MsDpo4: a Y-family DNA polymerase from Mycobacterium smegmatis. Acta Crystallogr Sect F Struct Biol Cryst Commun 2011; 67:812-6. [PMID: 21795801 PMCID: PMC3144803 DOI: 10.1107/s1744309111019063] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2011] [Accepted: 05/19/2011] [Indexed: 11/10/2022]
Abstract
The expression of error-prone DNA polymerases belonging to the Y-family is upregulated in prokaryotes under adverse conditions to facilitate adaptive mutagenesis. However, it has been suggested that representatives of this family in mycobacteria do not participate in adaptive mutagenesis. These studies raise the possibility that mycobacterial representatives might be devoid of biochemical activity. In order to determine whether this possible loss of activity is a consequence of significant changes in the structure of these enzymes, structural studies on a representative enzyme from Mycobacterium smegmatis, MsDpo4, were initiated. The protein crystallized in space group P6(1)22 or P6(5)22. The Matthews coefficient was 4.0 Å3 Da(-1) assuming the presence of one molecule in the asymmetric unit; the corresponding solvent content was 69%. X-ray diffraction data were collected to a minimum Bragg spacing of 2.6 Å and crystals of selenomethionine-labelled MsDpo4 have been prepared for ab initio phasing.
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Affiliation(s)
- Amit Sharma
- National Centre for Biological Sciences (NCBS–TIFR), UAS GKVK Campus, Bellary Road, Bangalore 560 065, India
| | - Deepak T. Nair
- National Centre for Biological Sciences (NCBS–TIFR), UAS GKVK Campus, Bellary Road, Bangalore 560 065, India
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Nair DT, Johnson RE, Prakash L, Prakash S, Aggarwal AK. DNA synthesis across an abasic lesion by yeast REV1 DNA polymerase. J Mol Biol 2010; 406:18-28. [PMID: 21167175 DOI: 10.1016/j.jmb.2010.12.016] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2010] [Revised: 12/03/2010] [Accepted: 12/07/2010] [Indexed: 10/18/2022]
Abstract
Abasic (apurinic/apyrimidinic) sites are among the most abundant DNA lesions in humans, and they present a strong block to replication. They are also highly mutagenic because when replicative DNA polymerases manage to insert a nucleotide opposite the lesion, they prefer to insert an A. Rev1, a member of Y-family DNA polymerases, does not obey the A-rule. This enzyme inserts a C opposite an abasic lesion with much greater catalytic efficiency than an A, G, or T. We present here the structure of yeast Rev1 in ternary complex with DNA containing an abasic lesion and with dCTP as the incoming nucleotide. The structure reveals a mechanism of synthesis across an abasic lesion that differs from that in other polymerases. The lesion is driven to an extrahelical position, and the incorporation of a C is mediated by an arginine (Arg324) that is conserved in all known orthologs of Rev1, including humans. The hydrophobic cavity that normally accommodates the unmodified G is instead filled with water molecules. Since Gs are especially prone to depurination through a spontaneous hydrolysis of the glycosidic bond, the ability of Rev1 to stabilize an abasic lesion in its active site and employ a surrogate arginine to incorporate a C provides a unique means for the "error-free" bypass of this noninstructional lesion.
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Affiliation(s)
- Deepak T Nair
- Department of Structural and Chemical Biology, Mount Sinai School of Medicine, Box 1677, 1425 Madison Avenue, New York, NY 10029, USA
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32
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Namadurai S, Jain D, Kulkarni DS, Tabib CR, Friedhoff P, Rao DN, Nair DT. The C-terminal domain of the MutL homolog from Neisseria gonorrhoeae forms an inverted homodimer. PLoS One 2010; 5:e13726. [PMID: 21060849 PMCID: PMC2965676 DOI: 10.1371/journal.pone.0013726] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2010] [Accepted: 09/23/2010] [Indexed: 01/07/2023] Open
Abstract
The mismatch repair (MMR) pathway serves to maintain the integrity of the genome by removing mispaired bases from the newly synthesized strand. In E. coli, MutS, MutL and MutH coordinate to discriminate the daughter strand through a mechanism involving lack of methylation on the new strand. This facilitates the creation of a nick by MutH in the daughter strand to initiate mismatch repair. Many bacteria and eukaryotes, including humans, do not possess a homolog of MutH. Although the exact strategy for strand discrimination in these organisms is yet to be ascertained, the required nicking endonuclease activity is resident in the C-terminal domain of MutL. This activity is dependent on the integrity of a conserved metal binding motif. Unlike their eukaryotic counterparts, MutL in bacteria like Neisseria exist in the form of a homodimer. Even though this homodimer would possess two active sites, it still acts a nicking endonuclease. Here, we present the crystal structure of the C-terminal domain (CTD) of the MutL homolog of Neisseria gonorrhoeae (NgoL) determined to a resolution of 2.4 Å. The structure shows that the metal binding motif exists in a helical configuration and that four of the six conserved motifs in the MutL family, including the metal binding site, localize together to form a composite active site. NgoL-CTD exists in the form of an elongated inverted homodimer stabilized by a hydrophobic interface rich in leucines. The inverted arrangement places the two composite active sites in each subunit on opposite lateral sides of the homodimer. Such an arrangement raises the possibility that one of the active sites is occluded due to interaction of NgoL with other protein factors involved in MMR. The presentation of only one active site to substrate DNA will ensure that nicking of only one strand occurs to prevent inadvertent and deleterious double stranded cleavage.
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Affiliation(s)
| | - Deepti Jain
- Laboratory 4, National Centre for Biological Sciences, Bangalore, India
| | | | - Chaitanya R. Tabib
- Department of Biochemistry, Indian Institute of Science, Bangalore, India
| | - Peter Friedhoff
- Institut für Biochemie (FB 08), Justus-Liebig-Universität, Giessen, Germany
| | - Desirazu N. Rao
- Department of Biochemistry, Indian Institute of Science, Bangalore, India
| | - Deepak T. Nair
- Laboratory 4, National Centre for Biological Sciences, Bangalore, India
- * E-mail:
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33
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Jain R, Nair DT, Johnson RE, Prakash L, Prakash S, Aggarwal AK. Replication across template T/U by human DNA polymerase-iota. Structure 2009; 17:974-80. [PMID: 19604477 DOI: 10.1016/j.str.2009.04.011] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2009] [Revised: 04/21/2009] [Accepted: 04/29/2009] [Indexed: 10/20/2022]
Abstract
Human DNA polymerase-iota (Poliota) incorporates correct nucleotides opposite template purines with a much higher efficiency and fidelity than opposite template pyrimidines. In fact, the fidelity opposite template T is so poor that Poliota inserts an incorrect dGTP approximately 10 times better than it inserts the correct dATP. We determine here how a template T/U is accommodated in the Poliota active site and why a G is incorporated more efficiently than an A. We show that in the absence of incoming dATP or dGTP (binary complex), template T/U exists in both syn and anti conformations, but in the presence of dATP or dGTP (ternary complexes), template T/U is predominantly in the anti conformation. We also show that dATP and dGTP insert differently opposite template T/U, and that the basis of selection of dGTP over dATP is a hydrogen bond between the N2 amino group of dGTP and Gln59 of Poliota.
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Affiliation(s)
- Rinku Jain
- Department of Structural and Chemical Biology, Mount Sinai School of Medicine, New York, NY 10029, USA
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34
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Nair DT, Johnson RE, Prakash L, Prakash S, Aggarwal AK. DNA synthesis across an abasic lesion by human DNA polymerase iota. Structure 2009; 17:530-7. [PMID: 19368886 DOI: 10.1016/j.str.2009.02.015] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2008] [Revised: 02/17/2009] [Accepted: 02/18/2009] [Indexed: 11/26/2022]
Abstract
Abasic sites are among the most abundant DNA lesions formed in human cells, and they present a strong block to replication. DNA polymerase iota (Poliota) is one of the few DNA Pols that does not follow the A-rule opposite an abasic site. We present here three structures of human Poliota in complex with DNAs containing an abasic lesion and dGTP, dTTP, or dATP as the incoming nucleotide. The structures reveal a mechanism of translesion synthesis across an abasic lesion that differs from that in other Pols. Both the abasic lesion and the incoming dNTPs are intrahelical and are closely apposed across a constricted active site cleft. The dNTPs partake in distinct networks of hydrogen bonds in the "void" opposite the lesion. These different patterns of hydrogen bonds, as well as stacking interactions, may underlie Poliota's small preference for insertion of dGTP over other nucleotides opposite this common lesion.
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Affiliation(s)
- Deepak T Nair
- Department of Structural and Chemical Biology, Mount Sinai School of Medicine, New York, NY 10029, USA
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35
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Nair DT, Johnson RE, Prakash L, Prakash S, Aggarwal AK. Protein-template-directed synthesis across an acrolein-derived DNA adduct by yeast Rev1 DNA polymerase. Structure 2008; 16:239-45. [PMID: 18275815 DOI: 10.1016/j.str.2007.12.009] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2007] [Revised: 12/10/2007] [Accepted: 12/10/2007] [Indexed: 10/22/2022]
Abstract
Acrolein is generated as the end product of lipid peroxidation and is also a ubiquitous environmental pollutant. Its reaction with the N2 of guanine leads to a cyclic gamma-HOPdG adduct that presents a block to normal replication. We show here that yeast Rev1 incorporates the correct nucleotide C opposite a permanently ring-closed form of gamma-HOPdG (PdG) with nearly the same efficiency as opposite an undamaged G. The structural basis of this action lies in the eviction of the PdG adduct from the Rev1 active site, and the pairing of incoming dCTP with a "surrogate" arginine residue. We also show that yeast Polzeta can carry out the subsequent extension reaction. Together, our studies reveal how the exocyclic PdG adduct is accommodated in a DNA polymerase active site, and they show that the combined action of Rev1 and Polzeta provides for accurate and efficient synthesis through this potentially carcinogenic DNA lesion.
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Affiliation(s)
- Deepak T Nair
- Department of Structural and Chemical Biology, Mount Sinai School of Medicine, Box 1677, 1425 Madison Avenue, New York, NY 10029, USA
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36
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Gupta YK, Nair DT, Wharton RP, Aggarwal AK. Structures of human Pumilio with noncognate RNAs reveal molecular mechanisms for binding promiscuity. Structure 2008; 16:549-57. [PMID: 18328718 DOI: 10.1016/j.str.2008.01.006] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2007] [Revised: 12/29/2007] [Accepted: 01/02/2008] [Indexed: 10/22/2022]
Abstract
Pumilio is a founder member of the evolutionarily conserved Puf family of RNA-binding proteins that control a number of physiological processes in eukaryotes. A structure of human Pumilio (hPum) Puf domain bound to a Drosophila regulatory sequence showed that each Puf repeat recognizes a single nucleotide. Puf domains in general bind promiscuously to a large set of degenerate sequences, but the structural basis for this promiscuity has been unclear. Here, we describe the structures of hPum Puf domain complexed to two noncognate RNAs, CycB(reverse) and Puf5. In each complex, one of the nucleotides is ejected from the binding surface, in effect, acting as a "spacer." The complexes also reveal the plasticity of several Puf repeats, which recognize noncanonical nucleotides. Together, these complexes provide a molecular basis for recognition of degenerate binding sites, which significantly increases the number of mRNAs targeted for regulation by Puf proteins in vivo.
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Affiliation(s)
- Yogesh K Gupta
- Department of Structural and Chemical Biology, Mount Sinai School of Medicine, Box 1677, 1425 Madison Avenue, New York, NY 10029, USA
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37
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Lone S, Townson SA, Uljon SN, Johnson RE, Brahma A, Nair DT, Prakash S, Prakash L, Aggarwal AK. Human DNA polymerase kappa encircles DNA: implications for mismatch extension and lesion bypass. Mol Cell 2007; 25:601-14. [PMID: 17317631 DOI: 10.1016/j.molcel.2007.01.018] [Citation(s) in RCA: 173] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2006] [Revised: 10/22/2006] [Accepted: 01/17/2007] [Indexed: 10/23/2022]
Abstract
Human DNA polymerase kappa (Pol kappa) is a proficient extender of mispaired primer termini on undamaged DNAs and is implicated in the extension step of lesion bypass. We present here the structure of Pol kappa catalytic core in ternary complex with DNA and an incoming nucleotide. The structure reveals encirclement of the DNA by a unique "N-clasp" at the N terminus of Pol kappa, which augments the conventional right-handed grip on the DNA by the palm, fingers, and thumb domains and the PAD and provides additional thermodynamic stability. The structure also reveals an active-site cleft that is constrained by the close apposition of the N-clasp and the fingers domain, and therefore can accommodate only a single Watson-Crick base pair. Together, DNA encirclement and other structural features help explain Pol kappa's ability to extend mismatches and to promote replication through various minor groove DNA lesions, by extending from the nucleotide incorporated opposite the lesion by another polymerase.
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Affiliation(s)
- Samer Lone
- Department of Structural and Chemical Biology, Mount Sinai School of Medicine, Box 1677, 1425 Madison Avenue, New York, NY 10029, USA
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38
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Nair DT, Johnson RE, Prakash L, Prakash S, Aggarwal AK. An incoming nucleotide imposes an anti to syn conformational change on the templating purine in the human DNA polymerase-iota active site. Structure 2006; 14:749-55. [PMID: 16615915 DOI: 10.1016/j.str.2006.01.010] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2005] [Revised: 01/12/2006] [Accepted: 01/12/2006] [Indexed: 10/24/2022]
Abstract
Substrate-induced conformational change of the protein is the linchpin of enzymatic reactions. Replicative DNA polymerases, for example, convert from an open to a closed conformation in response to dNTP binding. Human DNA polymerase-iota (hPoliota), a member of the Y family of DNA polymerases, differs strikingly from other polymerases in its much higher proficiency and fidelity for nucleotide incorporation opposite template purines than opposite template pyrimidines. We present here a crystallographic analysis of hPoliota binary complexes, which together with the ternary complexes show that, contrary to replicative DNA polymerases, the DNA, and not the polymerase, undergoes the primary substrate-induced conformational change. The incoming dNTP "pushes" templates A and G from the anti to the syn conformation dictated by a rigid hPoliota active site. Together, the structures posit a mechanism for template selection wherein dNTP binding induces a conformational switch in template purines for productive Hoogsteen base pairing.
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Affiliation(s)
- Deepak T Nair
- Structural Biology Program, Department of Physiology and Biophysics, Mount Sinai School of Medicine, Box 1677, 1425 Madison Avenue, New York, New York 10029, USA
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39
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Nair DT, Johnson RE, Prakash L, Prakash S, Aggarwal AK. Hoogsteen base pair formation promotes synthesis opposite the 1,N6-ethenodeoxyadenosine lesion by human DNA polymerase iota. Nat Struct Mol Biol 2006; 13:619-25. [PMID: 16819516 DOI: 10.1038/nsmb1118] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2006] [Accepted: 06/05/2006] [Indexed: 11/08/2022]
Abstract
The 1,N6-ethenodeoxyadenosine (epsilon dA) lesion is promutagenic and has been implicated in carcinogenesis. We show here that human Pol iota, a Y-family DNA polymerase, can promote replication through this lesion by proficiently incorporating a nucleotide opposite it. The structural basis of this action is rotation of the epsilon dA adduct to the syn conformation in the Pol iota active site and presentation of its 'Hoogsteen edge' for hydrogen-bonding with incoming dTTP or dCTP. We also show that Pol zeta carries out the subsequent extension reaction and that efficiency of extension from epsilon dA x T is notably higher than from epsilon dA x C. Together, our studies reveal for the first time how the exocyclic epsilon dA adduct is accommodated in a DNA polymerase active site, and they show that the combined action of Pol iota and Pol zeta provides for efficient and error-free synthesis through this potentially carcinogenic DNA lesion.
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Affiliation(s)
- Deepak T Nair
- Department of Molecular Physiology and Biophysics, Mount Sinai School of Medicine, Box 1677, 1425 Madison Avenue, New York, New York 10029, USA
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40
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Nair DT, Johnson RE, Prakash L, Prakash S, Aggarwal AK. Human DNA polymerase iota incorporates dCTP opposite template G via a G.C + Hoogsteen base pair. Structure 2006; 13:1569-77. [PMID: 16216587 DOI: 10.1016/j.str.2005.08.010] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2005] [Revised: 08/08/2005] [Accepted: 08/13/2005] [Indexed: 11/30/2022]
Abstract
Human DNA polymerase iota (hPoliota), a member of the Y family of DNA polymerases, differs in remarkable ways from other DNA polymerases, incorporating correct nucleotides opposite template purines with a much higher efficiency and fidelity than opposite template pyrimidines. We present here the crystal structure of hPoliota bound to template G and incoming dCTP, which reveals a G.C + Hoogsteen base pair in a DNA polymerase active site. We show that the hPoliota active site has evolved to favor Hoogsteen base pairing, wherein the template sugar is fixed in a cavity that reduces the C1'-C1' distance across the nascent base pair from approximately 10.5 A in other DNA polymerases to 8.6 A in hPoliota. The rotation of G from anti to syn is then largely in response to this curtailed C1'-C1' distance. A G.C+ Hoogsteen base pair suggests a specific mechanism for hPoliota's ability to bypass N(2)-adducted guanines that obstruct replication.
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Affiliation(s)
- Deepak T Nair
- Structural Biology Program, Department of Physiology and Biophysics, Mount Sinai School of Medicine, Box 1677, 1425 Madison Avenue, New York, New York 10029, USA
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41
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Abstract
The Rev1 DNA polymerase is highly specialized for the incorporation of C opposite template G. We present here the crystal structure of yeast Rev1 bound to template G and incoming 2'-deoxycytidine 5'-triphosphate (dCTP), which reveals that the polymerase itself dictates the identity of the incoming nucleotide, as well as the identity of the templating base. Template G and incoming dCTP do not pair with each other. Instead, the template G is evicted from the DNA helix, and it makes optimal hydrogen bonds with a segment of Rev1. Also, unlike other DNA polymerases, incoming dCTP pairs with an arginine rather than the templating base, which ensures the incorporation of dCTP over other incoming nucleotides. This mechanism provides an elegant means for promoting proficient and error-free synthesis through N2-adducted guanines that obstruct replication.
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Affiliation(s)
- Deepak T Nair
- Structural Biology Program, Department of Physiology and Biophysics, Mount Sinai School of Medicine, Box 1677, 1425 Madison Avenue, New York, NY 10029, USA
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42
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Nair DT, Johnson RE, Prakash S, Prakash L, Aggarwal AK. Replication by human DNA polymerase-iota occurs by Hoogsteen base-pairing. Nature 2004; 430:377-80. [PMID: 15254543 DOI: 10.1038/nature02692] [Citation(s) in RCA: 244] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2004] [Accepted: 05/28/2004] [Indexed: 11/09/2022]
Abstract
Almost all DNA polymerases show a strong preference for incorporating the nucleotide that forms the correct Watson-Crick base pair with the template base. In addition, the catalytic efficiencies with which any given polymerase forms the four possible correct base pairs are roughly the same. Human DNA polymerase-iota (hPoliota), a member of the Y family of DNA polymerases, is an exception to these rules. hPoliota incorporates the correct nucleotide opposite a template adenine with a several hundred to several thousand fold greater efficiency than it incorporates the correct nucleotide opposite a template thymine, whereas its efficiency for correct nucleotide incorporation opposite a template guanine or cytosine is intermediate between these two extremes. Here we present the crystal structure of hPoliota bound to a template primer and an incoming nucleotide. The structure reveals a polymerase that is 'specialized' for Hoogsteen base-pairing, whereby the templating base is driven to the syn conformation. Hoogsteen base-pairing offers a basis for the varied efficiencies and fidelities of hPoliota opposite different template bases, and it provides an elegant mechanism for promoting replication through minor-groove purine adducts that interfere with replication.
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Affiliation(s)
- Deepak T Nair
- Structural Biology Program, Department of Physiology and Biophysics, Mount Sinai School of Medicine, Box 1677, 1425 Madison Avenue, New York, New York 10029, USA
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Nair DT, Kaur KJ, Singh K, Mukherjee P, Rajagopal D, George A, Bal V, Rath S, Rao KVS, Salunke DM. Mimicry of native peptide antigens by the corresponding retro-inverso analogs is dependent on their intrinsic structure and interaction propensities. J Immunol 2003; 170:1362-73. [PMID: 12538696 DOI: 10.4049/jimmunol.170.3.1362] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Retro-inverso (ri) analogs of model T cell and B cell epitopes were predictively designed as mimics and then assayed for activity to understand the basis of functional ri-antigenic peptide mimicry. ri versions of two MHC class I binding peptide epitopes, one from a vesicular stomatitis virus glycoprotein (VSV(p)) and another from OVA (OVAp), exhibit structural as well as functional mimicry of their native counterparts. The two ri peptides exhibit conformational plasticity and they bind to MHC class I (H-2K(b)) similar to their native counterparts both in silico and in vivo. In fact, ri-OVAp is also presented to an OVAp-specific T cell line in a mode similar to native OVAp. In contrast, the ri version of an immunodominant B cell peptide epitope from a hepatitis B virus protein, PS1, exhibits no structural or functional correlation with its native counterpart. PS1 and its ri analog do not exhibit similar conformational propensities. PS1 is less flexible relative to its ri version. These observed structure-function relationships of the ri-peptide epitopes are consistent with the differences in recognition properties between peptide-MHC vs peptide-Ab binding where, while the recognition of the epitope by MHC is pattern based, the exquisitely specific recognition of Ag by Ab arises from the high complementarity between the Ag and the binding site of the Ab. It is evident that the correlation of conformational and interaction propensities of native L-peptides and their ri counterparts depends both on their inherent structural properties and on their mode of recognition.
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Nair DT, Singh K, Siddiqui Z, Nayak BP, Rao KVS, Salunke DM. Epitope recognition by diverse antibodies suggests conformational convergence in an antibody response. J Immunol 2002; 168:2371-82. [PMID: 11859128 DOI: 10.4049/jimmunol.168.5.2371] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Crystal structures of distinct mAbs that recognize a common epitope of a peptide Ag have been determined and analyzed in the unbound and bound forms. These Abs display dissimilar binding site structures in the absence of the Ag. The dissimilarity is primarily expressed in the conformations of complementarity-determining region H3, which is responsible for defining the epitope specificity. Interestingly, however, the three Abs exhibit similar complementarity-determining region conformations in the Ag binding site while recognizing the common epitope, indicating that different pathways of binding are used for Ag recognition. The epitope also exhibits conformational similarity when bound to each of these Abs, although the peptide Ag was otherwise flexible. The observed conformational convergence in the epitope and the Ag binding site was facilitated by the plasticity in the nature of interactions.
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Affiliation(s)
- Deepak T Nair
- Structural Biology Unit, National Institute of Immunology, New Delhi 110067, India
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45
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Jain D, Nair DT, Swaminathan GJ, Abraham EG, Nagaraju J, Salunke DM. Structure of the induced antibacterial protein from tasar silkworm, Antheraea mylitta. Implications to molecular evolution. J Biol Chem 2001; 276:41377-82. [PMID: 11522783 DOI: 10.1074/jbc.m104674200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The crystal structure of an antibacterial protein of immune origin (TSWAB), purified from tasar silkworm (Antheraea mylitta) larvae after induction by Escherichia coli infection, has been determined. This is the first insect lysozyme structure and represents induced lysozymes of innate immunity. The core structure of TSWAB is similar to c-type lysozymes and alpha-lactalbumins. However, TSWAB shows significant differences with respect to the other two proteins in the exposed loop regions. The catalytic residues in TSWAB are conserved with respect to the chicken lysozyme, indicating a common mechanism of action. However, differences in the noncatalytic residues in the substrate binding groove imply subtle differences in the specificity and the level of activity. Thus, conformational differences between TSWAB and chicken lysozyme exist, whereas functional mechanisms appear to be similar. On the other hand, alpha-lactalbumins and c-type lysozymes exhibit drastically different functions with conserved molecular conformation. It is evident that a common molecular scaffold is exploited in the three enzymes for apparently different physiological roles. It can be inferred on the basis of the structure-function comparison of these three proteins having common phylogenetic origin that the conformational changes in a protein are minimal during rapid evolution as compared with those in the normal course of evolution.
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Affiliation(s)
- D Jain
- National Institute of Immunology, New Delhi 110 067, India
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46
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Nayak SK, Bagga S, Gaur D, Nair DT, Salunke DM, Batra JK. Mechanism of specific target recognition and RNA hydrolysis by ribonucleolytic toxin restrictocin. Biochemistry 2001; 40:9115-24. [PMID: 11478878 DOI: 10.1021/bi010923m] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Restrictocin, a member of the fungal ribotoxin family, specifically cleaves a single phosphodiester bond in the 28S rRNA and potently inhibits eukaryotic protein synthesis. Residues Tyr47, His49, Glu95, Phe96, Pro97, Arg120, and His136 have been predicted to form the active site of restrictocin. In this study, we have individually mutated these amino acids to alanine to probe their role in restrictocin structure and function. The role of Tyr47, His49, Arg120, and His136 was further investigated by making additional mutants. Mutating Arg120 or His136 to alanine or the other amino acids rendered the toxin completely inactive, whereas mutating Glu95 to alanine only partially inactivated the toxin. Mutation of Phe96 and Pro97 to Ala had no effect on the activity of restrictocin. The Tyr47 to alanine mutant was inactive in inhibiting protein synthesis, and had a nonspecific ribonuclease activity on 28S rRNA similar to that shown previously for the His49 to Ala mutant. Unlike the His136 to Ala mutant, the double mutants containing Tyr47 or His49 mutated to alanine along with His136 did not compete with restrictocin to cause a significant reduction in the extent of cleavage of 28S rRNA. In a model of restrictocin and a 29-mer RNA substrate complex, residues Tyr47, His49, Glu95, Arg120, and His136 were found to be near the cleavage site on RNA. It is proposed that in restrictocin Glu95 and His136 are directly involved in catalysis, Arg120 is involved in the stabilization of the enzyme-substrate complex, Tyr47 provides structural stability to the active site, and His49 determines the substrate specificity.
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Affiliation(s)
- S K Nayak
- Immunochemistry Laboratory, National Institute of Immunology, Aruna Asaf Ali Road, New Delhi 110067, India
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Nair DT, Singh K, Sahu N, Rao KV, Salunke DM. Crystal structure of an antibody bound to an immunodominant peptide epitope: novel features in peptide-antibody recognition. J Immunol 2000; 165:6949-55. [PMID: 11120821 DOI: 10.4049/jimmunol.165.12.6949] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The crystal structure of Fab of an Ab PC283 complexed with its corresponding peptide Ag, PS1 (HQLDPAFGANSTNPD), derived from the hepatitis B virus surface Ag was determined. The PS1 stretch Gln2P to Phe7P is present in the Ag binding site of the Ab, while the next three residues of the peptide are raised above the binding groove. The residues Ser11P, Thr12P, and Asn13P then loop back onto the Ag-binding site of the Ab. The last two residues, Pro14P and Asp15P, extend outside the binding site without forming any contacts with the Ab. The PC283-PS1 complex is among the few examples where the light chain complementarity-determining regions show more interactions than the heavy chain complementarity-determining regions, and a distal framework residue is involved in Ag binding. As seen from the crystal structure, most of the contacts between peptide and Ab are through the five residues, Leu3-Asp4-Pro5-Ala6-Phe7, of PS1. The paratope is predominantly hydrophobic with aromatic residues lining the binding pocket, although a salt bridge also contributes to stabilizing the Ag-Ab interaction. The molecular surface area buried upon PS1 binding is 756 A(2) for the peptide and 625 A(2) for the Fab, which is higher than what has been seen to date for Ab-peptide complexes. A comparison between PC283 structure and a homology model of its germline ancestor suggests that paratope optimization for PS1 occurs by improving both charge and shape complementarity.
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Affiliation(s)
- D T Nair
- National Institute of Immunology and International Center of Genetic Engineering and Biotechnology, New Delhi, India
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