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Van Galen CJ, Pauszek RF, Koder RL, Stanley RJ. Flavin Charge Redistribution upon Optical Excitation Is Independent of Solvent Polarity. J Phys Chem B 2023; 127:661-672. [PMID: 36649202 DOI: 10.1021/acs.jpcb.2c07266] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Flavin absorption spectra encode molecular details of the flavin's local environment through coupling of local electric fields with the chromophore's charge redistribution upon optical excitation. Translating experimentally measured field-tuned transition energies to local electric field magnitudes and directions across a wide range of field magnitudes requires that the charge redistribution be independent of the local field. We have measured the charge redistribution upon optical excitation of the derivatized flavin TPARF in the non-hydrogen-bonding, nonpolar solvent toluene, with and without a tridentate hydrogen-bonding ligand, DBAP, using electronic Stark spectroscopy. These measurements were interpreted using TD-DFT finite field and difference density calculations. In comparing our present results to previous Stark spectroscopic analyses of flavin in more polar solvents, we conclude that flavin charge redistribution upon optical excitation is independent of solvent polarity, indicating that dependence of flavin transition energies on local field magnitude is linear with local field magnitude.
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Affiliation(s)
- Cornelius J Van Galen
- Department of Chemistry, Temple University, 1901 N. 13th St., 250B Beury Hall, Philadelphia, Pennsylvania19122, United States
| | - Raymond F Pauszek
- Department of Chemistry, Temple University, 1901 N. 13th St., 250B Beury Hall, Philadelphia, Pennsylvania19122, United States
| | - Ronald L Koder
- Department of Physics, The City College of New York, 1.308 CDI Bldg., 85 St. Nicholas Terrace, New York, New York10031, United States
| | - Robert J Stanley
- Department of Chemistry, Temple University, 1901 N. 13th St., 250B Beury Hall, Philadelphia, Pennsylvania19122, United States
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Musila JM, Rokita SE. Sequence Conservation Does Not Always Signify a Functional Imperative as Observed in the Nitroreductase Superfamily. Biochemistry 2022; 61:703-711. [PMID: 35319879 PMCID: PMC9018611 DOI: 10.1021/acs.biochem.2c00037] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Consensus sequences have the potential to help classify the structure and function of proteins and highlight key regions that may contribute to their biological properties. Often, the level of significance will track with the extent of sequence conservation, but this should not be considered universal. Arg and Lys dominate a position adjacent to the N1 and C2 carbonyl of flavin mononucleotide (FMN) bound in the proteins of the nitroreductase superfamily. Although this placement satisfies expectations for stabilizing the reduced form of FMN, the substitution of these residues in three subfamilies promoting distinct reactions demonstrates their importance to catalysis as only modest. Replacing Arg34 with Lys, Gln, or Glu enhances FMN binding to a flavin destructase (BluB) by twofold and diminishes FMN turnover by no more than 25%. Similarly, replacing Lys14 with Arg, Gln, or Glu in a nitroreductase (NfsB) does not perturb the binding of the substrate nitrofurazone. The catalytic efficiency does decrease by 21-fold for the K14Q variant, but no change in the midpoint potential of FMN was observed with any of the variants. Equivalent substitution at Arg38 in iodotyrosine deiodinase (IYD) affects catalysis even more modestly (<10-fold). While the Arg/Lys to Glu substitution inactivates NfsB and IYD, this change also stabilizes one-electron transfer in IYD contrary to predictions based on other classes of flavoproteins. Accordingly, functional correlations developed in certain structural superfamilies may not necessarily translate well to other superfamilies.
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Affiliation(s)
- Jonathan M Musila
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Steven E Rokita
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
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Kayastha K, Vitt S, Buckel W, Ermler U. Flavins in the electron bifurcation process. Arch Biochem Biophys 2021; 701:108796. [PMID: 33609536 DOI: 10.1016/j.abb.2021.108796] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Revised: 02/01/2021] [Accepted: 02/03/2021] [Indexed: 11/18/2022]
Abstract
The discovery of a new energy-coupling mechanism termed flavin-based electron bifurcation (FBEB) in 2008 revealed a novel field of application for flavins in biology. The key component is the bifurcating flavin endowed with strongly inverted one-electron reduction potentials (FAD/FAD•- ≪ FAD•-/FADH-) that cooperatively transfers in its reduced state one low and one high-energy electron into different directions and thereby drives an endergonic with an exergonic reduction reaction. As energy splitting at the bifurcating flavin apparently implicates one-electron chemistry, the FBEB machinery has to incorporate prior to and behind the central bifurcating flavin 2e-to-1e and 1e-to-2e switches, frequently also flavins, for oxidizing variable medium-potential two-electron donating substrates and for reducing high-potential two-electron accepting substrates. The one-electron carriers ferredoxin or flavodoxin serve as low-potential (high-energy) electron acceptors, which power endergonic processes almost exclusively in obligate anaerobic microorganisms to increase the efficiency of their energy metabolism. In this review, we outline the global organization of FBEB enzymes, the functions of the flavins therein and the surrounding of the isoalloxazine rings by which their reduction potentials are specifically adjusted in a finely tuned energy landscape.
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Affiliation(s)
- Kanwal Kayastha
- Max-Planck-Institut für Biophysik, Max-von-Laue-Str. 3, 60438, Frankfurt am Main, Germany
| | - Stella Vitt
- Max-Planck-Institut für Biophysik, Max-von-Laue-Str. 3, 60438, Frankfurt am Main, Germany; Laboratorium für Mikrobiologie, Fachbereich Biologie and SYNMIKRO, Philipps-Universität, 35032, Marburg, Germany
| | - Wolfgang Buckel
- Laboratorium für Mikrobiologie, Fachbereich Biologie and SYNMIKRO, Philipps-Universität, 35032, Marburg, Germany; Max-Planck-Institut für terrestrische Mikrobiologie, Karl-von-Frisch-Str. 10, 35043, Marburg, Germany
| | - Ulrich Ermler
- Max-Planck-Institut für Biophysik, Max-von-Laue-Str. 3, 60438, Frankfurt am Main, Germany.
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Pan F, Luo HJ, Wu ZY, Chen SZ, Wang X, Yu SX, Wang JM, Lin SY, Cai ZY, Gao YL, Zhuang PT, Xu LY, Li EM. Decreased plasma riboflavin is associated with poor prognosis, invasion, and metastasis in esophageal squamous cell carcinoma. Eur J Clin Nutr 2020; 74:1149-1156. [PMID: 32060383 DOI: 10.1038/s41430-020-0585-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Revised: 02/01/2020] [Accepted: 02/04/2020] [Indexed: 02/05/2023]
Abstract
BACKGROUND Riboflavin deficiency confers a predisposition for esophageal cancer. The role of plasma riboflavin levels in development and prognosis of individuals with digestive tract inflammation and ulcer (DTIU), digestive tract polyps (DTPs), and ESCC is not well understood. METHODS We performed a cross-sectional study, including 177 DTIU, 80 DTP, and 324 ESCC cases, to measure the plasma riboflavin levels among the three populations. Correlation between plasma riboflavin levels (categorized as ≥31.8, 6.5-31.8 and ≤6.5 nmol/L groups) and clinical characteristics, as well as survival of ESCC patients (556 cases) was analyzed. RESULTS There was no difference in plasma riboflavin levels between DTIU, DTP, and ESCC cases (P > 0.05). Plasma riboflavin levels were inversely correlated with invasive depth (correlation coefficient = -0.09, P = 0.026) and lymph node metastasis (correlation coefficient = -0.11, P = 0.010) of ESCC, and ESCC patients with low riboflavin levels had poor recurrence-free survival (P = 0.035) and overall survival (P = 0.003). Decreased riboflavin was a prognostic factor for poor overall survival (HR = 1.91, 95% CI = 1.19-3.07, P = 0.007). CONCLUSIONS Plasma riboflavin levels in DTIU, DTP, and ESCC patients are similar. Plasma riboflavin levels are associated with the development and prognosis of ESCC.
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Affiliation(s)
- Feng Pan
- Key Laboratory of Molecular Biology for High Cancer Incidence Coastal Chaoshan Area, Shantou University Medical College, Shantou, 515041, China
- Department of Biochemistry and Molecular Biology, Shantou University Medical College, No. 22, Xinling Road, Shantou, 515041, China
| | - Hong-Jun Luo
- Central Laboratory, Shantou University Medical College, Shantou, 515041, China
| | - Zhi-Yong Wu
- Department of Tumor Surgery, Shantou Central Hospital, Affiliated Shantou Hospital of Sun Yat-sen University, Shantou, 515031, China
| | - Su-Zuan Chen
- Department of Gastroenterology, The First Affiliated Hospital, Shantou University Medical College, Shantou, 515041, China
| | - Xuan Wang
- Key Laboratory of Molecular Biology for High Cancer Incidence Coastal Chaoshan Area, Shantou University Medical College, Shantou, 515041, China
- Institute of Oncologic Pathology, Shantou University Medical College, No. 22, Xinling Road, Shantou, 515041, China
| | - Shuai-Xia Yu
- Key Laboratory of Molecular Biology for High Cancer Incidence Coastal Chaoshan Area, Shantou University Medical College, Shantou, 515041, China
- Institute of Oncologic Pathology, Shantou University Medical College, No. 22, Xinling Road, Shantou, 515041, China
| | - Jia-Min Wang
- Key Laboratory of Molecular Biology for High Cancer Incidence Coastal Chaoshan Area, Shantou University Medical College, Shantou, 515041, China
- Institute of Oncologic Pathology, Shantou University Medical College, No. 22, Xinling Road, Shantou, 515041, China
| | - Shu-Yuan Lin
- Key Laboratory of Molecular Biology for High Cancer Incidence Coastal Chaoshan Area, Shantou University Medical College, Shantou, 515041, China
- Institute of Oncologic Pathology, Shantou University Medical College, No. 22, Xinling Road, Shantou, 515041, China
| | - Ze-Ying Cai
- Key Laboratory of Molecular Biology for High Cancer Incidence Coastal Chaoshan Area, Shantou University Medical College, Shantou, 515041, China
- Institute of Oncologic Pathology, Shantou University Medical College, No. 22, Xinling Road, Shantou, 515041, China
| | - Yu-Lin Gao
- Key Laboratory of Molecular Biology for High Cancer Incidence Coastal Chaoshan Area, Shantou University Medical College, Shantou, 515041, China
- Institute of Oncologic Pathology, Shantou University Medical College, No. 22, Xinling Road, Shantou, 515041, China
| | - Pei-Tong Zhuang
- Key Laboratory of Molecular Biology for High Cancer Incidence Coastal Chaoshan Area, Shantou University Medical College, Shantou, 515041, China
- Department of Biochemistry and Molecular Biology, Shantou University Medical College, No. 22, Xinling Road, Shantou, 515041, China
| | - Li-Yan Xu
- Key Laboratory of Molecular Biology for High Cancer Incidence Coastal Chaoshan Area, Shantou University Medical College, Shantou, 515041, China.
- Institute of Oncologic Pathology, Shantou University Medical College, No. 22, Xinling Road, Shantou, 515041, China.
| | - En-Min Li
- Key Laboratory of Molecular Biology for High Cancer Incidence Coastal Chaoshan Area, Shantou University Medical College, Shantou, 515041, China.
- Department of Biochemistry and Molecular Biology, Shantou University Medical College, No. 22, Xinling Road, Shantou, 515041, China.
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Bull JN, Carrascosa E, Giacomozzi L, Bieske EJ, Stockett MH. Ion mobility action spectroscopy of flavin dianions reveals deprotomer-dependent photochemistry. Phys Chem Chem Phys 2018; 20:19672-19681. [PMID: 30014081 PMCID: PMC6063075 DOI: 10.1039/c8cp03244k] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Photo-induced proton transfer, deprotomer-dependent photochemistry, and intramolecular charge transfer in flavin anions are investigated using action spectroscopy.
The intrinsic optical properties and photochemistry of flavin adenine dinucleotide (FAD) dianions are investigated using a combination of tandem ion mobility spectrometry and action spectroscopy. Two principal isomers are observed, the more stable form being deprotonated on the isoalloxazine group and a phosphate (N-3,PO4 deprotomer), and the other on the two phosphates (PO4,PO4 deprotomer). Ion mobility data and electronic action spectra suggest that photo-induced proton transfer occurs from the isoalloxazine group to a phosphate group, converting the PO4,PO4 deprotomer to the N-3,PO4 deprotomer. Comparisons of the isomer selective action spectra of FAD dianions and flavin monoanions with solution spectra and gas-phase photodissociation action spectra suggests that solvation shifts the electronic absorption of the deprotonated isoalloxazine group to higher energy. This is interpreted as evidence for significant charge transfer in the lowest optical transition of deprotonated isoalloxazine. Overall, this work demonstrates that the site of deprotonation of flavin anions strongly affects their electronic absorptions and photochemistry.
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Affiliation(s)
- James N Bull
- School of Chemistry, University of Melbourne, Melbourne, VIC 3010, Australia
| | - Eduardo Carrascosa
- School of Chemistry, University of Melbourne, Melbourne, VIC 3010, Australia
| | | | - Evan J Bieske
- School of Chemistry, University of Melbourne, Melbourne, VIC 3010, Australia
| | - Mark H Stockett
- School of Chemistry, University of Melbourne, Melbourne, VIC 3010, Australia and Department of Physics, Stockholm University, Stockholm, Sweden.
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Zhu X, Wentworth P, Kyle RA, Lerner RA, Wilson IA. Cofactor-containing antibodies: crystal structure of the original yellow antibody. Proc Natl Acad Sci U S A 2006; 103:3581-5. [PMID: 16537445 PMCID: PMC1450126 DOI: 10.1073/pnas.0600251103] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Antibodies are generally thought to be a class of proteins that function without the use of cofactors. However, it is not widely appreciated that antibodies are believed to be the major carrier protein in human circulation for the important riboflavin cofactor that is involved in a host of biological phenomena. A further link between riboflavin and antibodies was discovered 30 years ago when a bright-yellow antibody, IgG(GAR), was purified from a patient with multiple myeloma who had turned yellow during the course of her disease. It was subsequently shown that the yellow color of this antibody was due to riboflavin binding. However, it was not known how and where riboflavin was bound to this antibody. We now report the crystal structure of this historically important IgG(GAR) Fab at 3.0-A resolution. The riboflavin is located in the antigen-combining site with its isoalloxazine ring stacked between the parallel aromatic moieties of TyrH33, PheH58, and TyrH100A. Together with additional hydrogen bonds, these interactions reveal the structural basis for high-affinity riboflavin binding. The ligand specificity of IgG(GAR) is compared with another riboflavin-binding antibody, IgG(DOT), which was purified from a second patient with multiple myeloma. The crystal structure of IgG(GAR) provides a starting point for attempts to understand the physiological relevance and chemical functions of cofactor-containing antibodies.
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Affiliation(s)
| | | | - Robert A. Kyle
- Division of Hematology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905
| | - Richard A. Lerner
- Departments of *Molecular Biology and
- Chemistry, and
- The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037; and
- To whom correspondence may be addressed. E-mail:
or
| | - Ian A. Wilson
- Departments of *Molecular Biology and
- The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037; and
- To whom correspondence may be addressed. E-mail:
or
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