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Imiołek M, Isenegger PG, Ng WL, Khan A, Gouverneur V, Davis BG. Residue-Selective Protein C-Formylation via Sequential Difluoroalkylation-Hydrolysis. ACS CENTRAL SCIENCE 2021; 7:145-155. [PMID: 33532577 PMCID: PMC7845020 DOI: 10.1021/acscentsci.0c01193] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Indexed: 05/16/2023]
Abstract
The carbonyl group is now a widely useful, nonproteinogenic functional group in chemical biology, yet methods for its generation in proteins have relied upon either cotranslational incorporation of unnatural amino acids bearing carbonyls or oxidative conversion (chemical or enzymatic) of existing natural amino acids. If available, alternative strategies for directly adding the C=O group through C-C bond-forming C-carbonylation, particularly at currently inaccessible amino acid sites, would provide a powerful method for adding valuable reactivity and expanding possible function in proteins. Here, following a survey of methods for HCF2· generation, we show that reductive photoredox catalysis enables mild radical-mediated difluoromethylation-hydrolysis of native protein residues as an effective method for carbonylation. Inherent selectivity of HCF2· allowed preferential modification of Trp residues. The resulting C-2-difluoromethylated Trp undergoes Reimer-Tiemann-type dehalogenation providing highly effective spontaneous hydrolytic collapse in proteins to carbonylated HC(O)-Trp (C-formyl-Trp = CfW) residues. This new, unnatural protein residue CfW not only was found to be effective in bioconjugation, ligation, and labeling reactions but also displayed strong "red-shifting" of its absorption and fluorescent emission maxima, allowing direct use of Trp sites as UV-visualized fluorophores in proteins and even cells. In this way, this method for the effective generation of masked formyl-radical "HC(O)·" equivalents enables first examples of C-C bond-forming carbonylation in proteins, thereby expanding the chemical reactivity and spectroscopic function that may be selectively and post-translationally "edited" into biology.
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Affiliation(s)
- Mateusz Imiołek
- Department
of Chemistry, University of Oxford, Oxford OX1 3TA, United Kingdom of Great Britain and Northern Ireland
- The
Rosalind Franklin Institute, Oxfordshire OX11 0FA, United Kingdom of
Great Britain and Northern Ireland
| | - Patrick G. Isenegger
- Department
of Chemistry, University of Oxford, Oxford OX1 3TA, United Kingdom of Great Britain and Northern Ireland
| | - Wai-Lung Ng
- Department
of Chemistry, University of Oxford, Oxford OX1 3TA, United Kingdom of Great Britain and Northern Ireland
| | - Aziz Khan
- Department
of Chemistry, University of Oxford, Oxford OX1 3TA, United Kingdom of Great Britain and Northern Ireland
| | - Véronique Gouverneur
- Department
of Chemistry, University of Oxford, Oxford OX1 3TA, United Kingdom of Great Britain and Northern Ireland
| | - Benjamin G. Davis
- Department
of Chemistry, University of Oxford, Oxford OX1 3TA, United Kingdom of Great Britain and Northern Ireland
- The
Rosalind Franklin Institute, Oxfordshire OX11 0FA, United Kingdom of
Great Britain and Northern Ireland
- ,
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Cook I, Asenjo AB, Sosa H, Leyh TS. The Human UGT2B7 Nanodisc. Drug Metab Dispos 2019; 48:198-204. [PMID: 31892527 DOI: 10.1124/dmd.119.089946] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Accepted: 12/30/2019] [Indexed: 01/01/2023] Open
Abstract
The 20 uridine diphosphate glycosyl-transferases (UGTs) encoded in the human genome form an essential homeostatic network of overlapping catalytic functions that surveil and regulate the activity and clearance of scores of small molecule metabolites. Biochemical and biophysical UGT studies have been hampered by the inability to purify these membrane-bound proteins. Here, using cell-free expression and nanodisc technology, we assemble and purify to homogeneity the first UGT nanodisc-the human UGT2B7•nanodisc. The complex is readily isolated in milligram quantities. It is stable and its initial-rate parameters are identical within error to those associated with UGT2B7 in microsomal preparations (i.e., Supersomes). The high purity of the nanodisc preparation simplifies UGT assays, which allows complexities traditionally associated with microsomal assays (latency and the albumin effect) to be circumvented. Each nanodisc is shown to harbor a single UGT2B7 monomer. The methods described herein should be widely applicable to UGTs, and these findings are expected to set the stage for experimentalists to more freely explore the structure, function, and biology of this important area of phase II metabolism. SIGNIFICANCE STATEMENT: Lack of access to pure, catalytically competent human uridine diphosphate glucuronosyl-transferases (UGTs) has long been an impediment to biochemical and biophysical studies of this disease-relevant enzyme family. Here, we demonstrate this barrier can be removed using nanodisc technology-a human UGT2B7•nanodisc is assembled, purified to homogeneity, and shown to have activity comparable to microsomal UGT2B7.
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Affiliation(s)
- Ian Cook
- Departments of Microbiology and Immunology (I.C., T.S.L.) and Physiology and Biophysics (A.B.A., H.S.), Albert Einstein College of Medicine, New York City, New York
| | - Anna B Asenjo
- Departments of Microbiology and Immunology (I.C., T.S.L.) and Physiology and Biophysics (A.B.A., H.S.), Albert Einstein College of Medicine, New York City, New York
| | - Hernando Sosa
- Departments of Microbiology and Immunology (I.C., T.S.L.) and Physiology and Biophysics (A.B.A., H.S.), Albert Einstein College of Medicine, New York City, New York
| | - Thomas S Leyh
- Departments of Microbiology and Immunology (I.C., T.S.L.) and Physiology and Biophysics (A.B.A., H.S.), Albert Einstein College of Medicine, New York City, New York
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Chopra A, Willmore WG, Biggar KK. Protein quantification and visualization via ultraviolet-dependent labeling with 2,2,2-trichloroethanol. Sci Rep 2019; 9:13923. [PMID: 31558752 PMCID: PMC6763483 DOI: 10.1038/s41598-019-50385-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Accepted: 09/09/2019] [Indexed: 11/09/2022] Open
Abstract
The incorporation of 2,2,2-trichloroethanol in polyacrylamide gels allows for fluorescent visualization of proteins following electrophoresis. Ultraviolet-light exposure, in the presence of this trichlorinated compound, results in a covalent modification of the tryptophan indole ring that shifts the fluorescent emission into the visible range. Based on this principle, we used 2,2,2-trichloroethanol to develop a microplate format protein quantification assay based on the fluorescent signal generated by modified proteins. We also demonstrated a specific fluorescent emission of 2,2,2-trichloroethanol-labeled protein at 450 nm, with a 310 nm excitation, resulting from modification of both tryptophan and tyrosine residues. Following optimization, this protein quantification assay displayed superior sensitivity when compared to UV absorbance at 280 nm (A280), and enabled quantification beyond the linear range permitted by the Bradford method. This 100 μL assay displayed a sensitivity of 10.5 μg in a range up to at least 200 μg. Furthermore, we extended the utility of this method through the development of a 20 μL low-volume assay, with a sensitivity of 8.7 μg tested up to 100 μg, which enabled visualization of proteins following SDS-PAGE. Collectively, these results demonstrate the utility of 2,2,2-trichloroethanol-based protein quantification and demonstrates the protein visualization in polyacrylamide gels based on 2,2,2-trichloroethanol-labeling pre-electrophoresis.
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Affiliation(s)
- Anand Chopra
- Department of Biology, Carleton University, 1125 Colonel By Dr, Ottawa, ON, K1S 5B6, Canada
| | - William G Willmore
- Department of Biology, Carleton University, 1125 Colonel By Dr, Ottawa, ON, K1S 5B6, Canada. .,Institute of Biochemistry, Carleton University, 1125 Colonel By Dr, Ottawa, ON, K1S 5B6, Canada. .,Department of Chemistry, Carleton University, 1125 Colonel By Dr, Ottawa, ON, K1S 5B6, Canada.
| | - Kyle K Biggar
- Department of Biology, Carleton University, 1125 Colonel By Dr, Ottawa, ON, K1S 5B6, Canada. .,Institute of Biochemistry, Carleton University, 1125 Colonel By Dr, Ottawa, ON, K1S 5B6, Canada.
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Ghatak SK, Dey D, Sen S, Sen K. Aromatic amino acids in high selectivity bismuth(iii) recognition. Analyst 2013; 138:2308-14. [DOI: 10.1039/c3an36842d] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Ladner CL, Turner RJ, Edwards RA. Development of indole chemistry to label tryptophan residues in protein for determination of tryptophan surface accessibility. Protein Sci 2007; 16:1204-13. [PMID: 17525468 PMCID: PMC2206665 DOI: 10.1110/ps.062728407] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Solvent accessibility can be used to evaluate protein structural models, identify binding sites, and characterize protein conformational changes. The differential modification of amino acids at specific sites enables the accessible surface residues to be identified by mass spectrometry. Tryptophan residues within proteins can be differentially labeled with halocompounds by a photochemical reaction. In this study, tryptophan residues of carbonic anhydrase are reacted with chloroform, 2,2,2-trichloroethanol (TCE), 2,2,2-trichloroacetate (TCA), or 3-bromo-1-propanol (BP) under UV irradiation at 280 nm. The light-driven reactions with chloroform, TCE, TCA, and BP attach a formyl, hydroxyethanone, carboxylic acid, and propanol group, respectively, onto the indole ring of tryptophan. Trypsin and chymotrypsin digests of the modified carbonic anhydrase are used to map accessible tryptophan residues using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Tryptophan reactivity is determined by identifying peptides with tryptophan residues modified with the appropriate label. The reactivity is calculated from the frequency that the modification is identified and a semiquantitative measure of the amount of products formed. Both of these measures of tryptophan reactivity correlate significantly with the accessible surface area of tryptophan residues in carbonic anhydrase determined from the X-ray crystal structure. Therefore the photochemical reaction of halocompounds with tryptophan residues in carbonic anhydrase indicates the degree of solvent accessibility of these residues.
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Affiliation(s)
- Carol L Ladner
- Department of Biological Sciences, University of Calgary, Calgary, AB T2N 1N4, Canada
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Clairmont CA, Sweasy JB. The Pol beta-14 dominant negative rat DNA polymerase beta mutator mutant commits errors during the gap-filling step of base excision repair in Saccharomyces cerevisiae. J Bacteriol 1998; 180:2292-7. [PMID: 9573177 PMCID: PMC107167 DOI: 10.1128/jb.180.9.2292-2297.1998] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
We demonstrated recently that dominant negative mutants of rat DNA polymerase beta (Pol beta) interfere with repair of alkylation damage in Saccharomyces cerevisiae. To identify the alkylation repair pathway that is disrupted by the Pol beta dominant negative mutants, we studied the epistatic relationship of the dominant negative Pol beta mutants to genes known to be involved in repair of DNA alkylation damage in S. cerevisiae. We demonstrate that the rat Pol beta mutants interfere with the base excision repair pathway in S. cerevisiae. In addition, expression of one of the Pol beta dominant negative mutants, Pol beta-14, increases the spontaneous mutation rate of S. cerevisiae whereas expression of another Pol beta dominant negative mutant, Pol beta-TR, does not. Expression of the Pol beta-14 mutant in cells lacking APN1 activity does not result in an increase in the spontaneous mutation rate. These results suggest that gaps are required for mutagenesis to occur in the presence of Pol beta-14 but that it is not merely the presence of a gap that results in mutagenesis. Our results suggest that mutagenesis can occur during the gap-filling step of base excision repair in vivo.
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Affiliation(s)
- C A Clairmont
- Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, Connecticut 06520, USA
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Papp SJ, Highsmith S. The ATP-induced myosin subfragment-1 fluorescence intensity increase is due to one tryptophan. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1202:169-72. [PMID: 8373821 DOI: 10.1016/0167-4838(93)90079-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The irradiation of skeletal muscle myosin subfragment 1 (S1) in the presence of 2,2,2-trichloroethanol (TCE) reduces S1 fluorescence intensity in two phases. In the first phase, there is an increase in MgATPase activity, and no significant change in the fluorescence intensity increase upon ATP binding. In the second phase, the activity remains elevated, but there is a complete loss of the ATP-induced intensity increase. Measurements on denatured S1 indicate that fluorescence intensity reductions of one fifth of the total occur during each of the two phases, consistent with the fluorescence intensity increase upon forming S1.MgADP.P(i) being due to one of the five heavy-chain tryptophans.
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Affiliation(s)
- S J Papp
- Department of Biochemistry, University of the Pacific School of Dentistry, San Francisco, CA 94115
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