Allosteric Inhibition of Human Ribonucleotide Reductase by dATP Entails the Stabilization of a Hexamer
Ribonucleotide reductases (RNRs) are responsible for all de novo biosynthesis of DNA precursors in nature by catalyzing the conversion of ribonucleotides to deoxyribonucleotides. Because of its essential role in cell division, human RNR is a target for a number of anticancer drugs in clinical use. L...
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| Format: | Article |
| Language: | en_US |
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American Chemical Society (ACS)
2017
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| Online Access: | http://hdl.handle.net/1721.1/108309 https://orcid.org/0000-0001-8076-4489 https://orcid.org/0000-0001-5486-2755 |
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| author | Asturias, Francisco J. Ando, Nozomi Li, Haoran Brignole, Edward J Thompson, Samuel M. McLaughlin, Martin I. Page, Julia E. Stubbe, JoAnne Drennan, Catherine L. |
| author2 | Massachusetts Institute of Technology. Department of Biology |
| author_facet | Massachusetts Institute of Technology. Department of Biology Asturias, Francisco J. Ando, Nozomi Li, Haoran Brignole, Edward J Thompson, Samuel M. McLaughlin, Martin I. Page, Julia E. Stubbe, JoAnne Drennan, Catherine L. |
| author_sort | Asturias, Francisco J. |
| collection | MIT |
| description | Ribonucleotide reductases (RNRs) are responsible for all de novo biosynthesis of DNA precursors in nature by catalyzing the conversion of ribonucleotides to deoxyribonucleotides. Because of its essential role in cell division, human RNR is a target for a number of anticancer drugs in clinical use. Like other class Ia RNRs, human RNR requires both a radical-generation subunit (β) and nucleotide-binding subunit (α) for activity. Because of their complex dependence on allosteric effectors, however, the active and inactive quaternary forms of many class Ia RNRs have remained in question. Here, we present an X-ray crystal structure of the human α subunit in the presence of inhibiting levels of dATP, depicting a ring-shaped hexamer (α[subscript 6]) where the active sites line the inner hole. Surprisingly, our small-angle X-ray scattering (SAXS) results indicate that human α forms a similar hexamer in the presence of ATP, an activating effector. In both cases, α[subscript 6] is assembled from dimers (α[subscript 2]) without a previously proposed tetramer intermediate (α[subscript 4]). However, we show with SAXS and electron microscopy that at millimolar ATP, the ATP-induced α[subscript 6] can further interconvert with higher-order filaments. Differences in the dATP- and ATP-induced α[subscript 6] were further examined by SAXS in the presence of the β subunit and by activity assays as a function of ATP or dATP. Together, these results suggest that dATP-induced α[subscript 6] is more stable than the ATP-induced α6 and that stabilization of this ring-shaped configuration provides a mechanism to prevent access of the β subunit to the active site of α. |
| first_indexed | 2024-09-23T11:32:43Z |
| format | Article |
| id | mit-1721.1/108309 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T11:32:43Z |
| publishDate | 2017 |
| publisher | American Chemical Society (ACS) |
| record_format | dspace |
| spelling | mit-1721.1/1083092022-10-01T04:21:24Z Allosteric Inhibition of Human Ribonucleotide Reductase by dATP Entails the Stabilization of a Hexamer Asturias, Francisco J. Ando, Nozomi Li, Haoran Brignole, Edward J Thompson, Samuel M. McLaughlin, Martin I. Page, Julia E. Stubbe, JoAnne Drennan, Catherine L. Massachusetts Institute of Technology. Department of Biology Massachusetts Institute of Technology. Department of Chemistry Ando, Nozomi Li, Haoran Brignole, Edward J Thompson, Samuel M. McLaughlin, Martin I. Page, Julia E. Stubbe, JoAnne Drennan, Catherine L. Ribonucleotide reductases (RNRs) are responsible for all de novo biosynthesis of DNA precursors in nature by catalyzing the conversion of ribonucleotides to deoxyribonucleotides. Because of its essential role in cell division, human RNR is a target for a number of anticancer drugs in clinical use. Like other class Ia RNRs, human RNR requires both a radical-generation subunit (β) and nucleotide-binding subunit (α) for activity. Because of their complex dependence on allosteric effectors, however, the active and inactive quaternary forms of many class Ia RNRs have remained in question. Here, we present an X-ray crystal structure of the human α subunit in the presence of inhibiting levels of dATP, depicting a ring-shaped hexamer (α[subscript 6]) where the active sites line the inner hole. Surprisingly, our small-angle X-ray scattering (SAXS) results indicate that human α forms a similar hexamer in the presence of ATP, an activating effector. In both cases, α[subscript 6] is assembled from dimers (α[subscript 2]) without a previously proposed tetramer intermediate (α[subscript 4]). However, we show with SAXS and electron microscopy that at millimolar ATP, the ATP-induced α[subscript 6] can further interconvert with higher-order filaments. Differences in the dATP- and ATP-induced α[subscript 6] were further examined by SAXS in the presence of the β subunit and by activity assays as a function of ATP or dATP. Together, these results suggest that dATP-induced α[subscript 6] is more stable than the ATP-induced α6 and that stabilization of this ring-shaped configuration provides a mechanism to prevent access of the β subunit to the active site of α. National Institutes of Health (U.S.) (GM100008) National Institutes of Health (U.S.) (Grant GM29595) Massachusetts Institute of Technology. Undergraduate Research Opportunities Program 2017-04-20T18:36:43Z 2017-04-20T18:36:43Z 2015-12 2015-11 Article http://purl.org/eprint/type/JournalArticle 0006-2960 1520-4995 http://hdl.handle.net/1721.1/108309 Ando, Nozomi et al. “Allosteric Inhibition of Human Ribonucleotide Reductase by dATP Entails the Stabilization of a Hexamer.” Biochemistry 55.2 (2016): 373–381. © 2015 American Chemical Society https://orcid.org/0000-0001-8076-4489 https://orcid.org/0000-0001-5486-2755 en_US http://dx.doi.org/10.1021/acs.biochem.5b01207 Biochemistry Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. application/pdf American Chemical Society (ACS) ACS |
| spellingShingle | Asturias, Francisco J. Ando, Nozomi Li, Haoran Brignole, Edward J Thompson, Samuel M. McLaughlin, Martin I. Page, Julia E. Stubbe, JoAnne Drennan, Catherine L. Allosteric Inhibition of Human Ribonucleotide Reductase by dATP Entails the Stabilization of a Hexamer |
| title | Allosteric Inhibition of Human Ribonucleotide Reductase by dATP Entails the Stabilization of a Hexamer |
| title_full | Allosteric Inhibition of Human Ribonucleotide Reductase by dATP Entails the Stabilization of a Hexamer |
| title_fullStr | Allosteric Inhibition of Human Ribonucleotide Reductase by dATP Entails the Stabilization of a Hexamer |
| title_full_unstemmed | Allosteric Inhibition of Human Ribonucleotide Reductase by dATP Entails the Stabilization of a Hexamer |
| title_short | Allosteric Inhibition of Human Ribonucleotide Reductase by dATP Entails the Stabilization of a Hexamer |
| title_sort | allosteric inhibition of human ribonucleotide reductase by datp entails the stabilization of a hexamer |
| url | http://hdl.handle.net/1721.1/108309 https://orcid.org/0000-0001-8076-4489 https://orcid.org/0000-0001-5486-2755 |
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