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Chao A, Burley KH, Sieminski PJ, de Miranda R, Chen X, Mobley DL, Goulding CW. Structure of a Mycobacterium tuberculosis Heme-Degrading Protein, MhuD, Variant in Complex with Its Product. Biochemistry 2019; 58:4610-4620. [PMID: 31638374 DOI: 10.1021/acs.biochem.9b00726] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis, requires iron for survival. In Mtb, MhuD is the cytosolic protein that degrades imported heme. MhuD is distinct, in both sequence and structure, from canonical heme oxygenases (HOs) but homologous with IsdG-type proteins. Canonical HO is found mainly in eukaryotes, while IsdG-type proteins are predominantly found in prokaryotes, including pathogens. While there are several published structures of MhuD and other IsdG-type proteins in complex with the heme substrate, no structures of IsdG-type proteins in complex with a product have been reported, unlike the case for HOs. We recently showed that the Mtb variant MhuD-R26S produces biliverdin IXα (αBV) rather than the wild-type mycobilin isomers. Given that mycobilin and other IsdG-type protein products like staphylobilin are difficult to isolate in quantities sufficient for structure determination, here we use the MhuD-R26S variant and its product αBV as a proxy to study the IsdG-type protein-product complex. First, we show that αBV has a nanomolar affinity for MhuD and the R26S variant. Second, we determined the MhuD-R26S-αBV complex structure to 2.5 Å, which reveals two notable features: (1) two αBV molecules bound per active site and (2) a novel α-helix (α3) that was not observed in previous MhuD-heme structures. Finally, through molecular dynamics simulations, we show that α3 is stable with the proximal αBV alone. MhuD's high affinity for the product and the observed structural and electrostatic changes that accompany substrate turnover suggest that there may be an unidentified class of proteins that are responsible for the extraction of products from MhuD and other IsdG-type proteins.
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Ahmed FH, Mohamed AE, Carr PD, Lee BM, Condic-Jurkic K, O'Mara ML, Jackson CJ. Rv2074 is a novel F420 H2 -dependent biliverdin reductase in Mycobacterium tuberculosis. Protein Sci 2016; 25:1692-709. [PMID: 27364382 DOI: 10.1002/pro.2975] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Accepted: 06/29/2016] [Indexed: 12/12/2022]
Abstract
Bilirubin is a potent antioxidant that is produced from the reduction of the heme degradation product biliverdin. In mammalian cells and Cyanobacteria, NADH/NADPH-dependent biliverdin reductases (BVRs) of the Rossmann-fold have been shown to catalyze this reaction. Here, we describe the characterization of Rv2074 from Mycobacterium tuberculosis, which belongs to a structurally and mechanistically distinct family of F420 H2 -dependent BVRs (F-BVRs) that are exclusively found in Actinobacteria. We have solved the crystal structure of Rv2074 bound to its cofactor, F420 , and used this alongside molecular dynamics simulations, site-directed mutagenesis and NMR spectroscopy to elucidate its catalytic mechanism. The production of bilirubin by Rv2074 could exploit the anti-oxidative properties of bilirubin and contribute to the range of immuno-evasive mechanisms that have evolved in M. tuberculosis to allow persistent infection.
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Affiliation(s)
- F Hafna Ahmed
- Research School of Chemistry, The Australian National University, Canberra, ACT, 2601, Australia
| | - A Elaaf Mohamed
- Research School of Chemistry, The Australian National University, Canberra, ACT, 2601, Australia
| | - Paul D Carr
- Research School of Chemistry, The Australian National University, Canberra, ACT, 2601, Australia
| | - Brendon M Lee
- Research School of Chemistry, The Australian National University, Canberra, ACT, 2601, Australia
| | - Karmen Condic-Jurkic
- Research School of Chemistry, The Australian National University, Canberra, ACT, 2601, Australia
| | - Megan L O'Mara
- Research School of Chemistry, The Australian National University, Canberra, ACT, 2601, Australia
| | - Colin J Jackson
- Research School of Chemistry, The Australian National University, Canberra, ACT, 2601, Australia
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Grobmyer SR, Jiang H. Looking at and listening to cancer cells. Chembiochem 2012; 13:1401-3. [PMID: 22615100 DOI: 10.1002/cbic.201200169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2012] [Indexed: 11/11/2022]
Affiliation(s)
- Stephen R Grobmyer
- Department of Surgery, University of Florida, 1600 SW Archer Road, Room 6164; Box 100109, Gainesville, FL 32609-0109, USA.
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Filonov GS, Krumholz A, Xia J, Yao J, Wang LV, Verkhusha VV. Deep-tissue photoacoustic tomography of a genetically encoded near-infrared fluorescent probe. Angew Chem Int Ed Engl 2011; 51:1448-51. [PMID: 22213541 DOI: 10.1002/anie.201107026] [Citation(s) in RCA: 148] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Indexed: 11/11/2022]
Affiliation(s)
- Grigory S Filonov
- Department of Anatomy and Structural Biology, and Gruss-Lipper Biophotonics Center, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
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Filonov GS, Krumholz A, Xia J, Yao J, Wang LV, Verkhusha VV. Deep-Tissue Photoacoustic Tomography of a Genetically Encoded Near-Infrared Fluorescent Probe. Angew Chem Int Ed Engl 2011. [DOI: 10.1002/ange.201107026] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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Watanabe A, Hirata K, Hagiwara Y, Yutani Y, Sugishima M, Yamamoto M, Fukuyama K, Wada K. Expression, purification and preliminary X-ray crystallographic analysis of cyanobacterial biliverdin reductase. Acta Crystallogr Sect F Struct Biol Cryst Commun 2011; 67:313-7. [PMID: 21393834 DOI: 10.1107/s1744309110053431] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2010] [Accepted: 12/20/2010] [Indexed: 01/24/2023]
Abstract
Biliverdin reductase (BVR) catalyzes the conversion of biliverdin IX α to bilirubin IX α with concomitant oxidation of an NADH or NADPH cofactor. This enzyme also binds DNA and enhances the transcription of specific genes. Recombinant cyanobacterial BVR was overexpressed in Escherichia coli, purified and crystallized. A native data set was collected to 2.34 Å resolution on beamline BL38B1 at SPring-8. An SeMet data set was collected from a microcrystal (300×10×10 µm) on the RIKEN targeted protein beamline BL32XU and diffraction spots were obtained to 3.0 Å resolution. The native BVR crystal belonged to space group P2(1)2(1)2(1), with unit-cell parameters a=58.8, b=88.4, c=132.6 Å. Assuming that two molecules are present in the asymmetric unit, VM (the Matthews coefficient) was calculated to be 2.37 Å3 Da(-1) and the solvent content was estimated to be 48.1%. The structure of cyanobacterial BVR may provide insights into the mechanisms of its enzymatic and physiological functions.
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Affiliation(s)
- Aya Watanabe
- Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
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Kohler AC, Gae DD, Richley MA, Stoll S, Gunn A, Lim S, Martin SS, Doukov TI, Britt RD, Ames JB, Lagarias JC, Fisher AJ. Structural basis for hydration dynamics in radical stabilization of bilin reductase mutants. Biochemistry 2010; 49:6206-18. [PMID: 20557110 DOI: 10.1021/bi100728q] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Heme-derived linear tetrapyrroles (phytobilins) in phycobiliproteins and phytochromes perform critical light-harvesting and light-sensing roles in oxygenic photosynthetic organisms. A key enzyme in their biogenesis, phycocyanobilin:ferredoxin oxidoreductase (PcyA), catalyzes the overall four-electron reduction of biliverdin IXalpha to phycocyanobilin--the common chromophore precursor for both classes of biliproteins. This interconversion occurs via semireduced bilin radical intermediates that are profoundly stabilized by selected mutations of two critical catalytic residues, Asp105 and His88. To understand the structural basis for this stabilization and to gain insight into the overall catalytic mechanism, we report the high-resolution crystal structures of substrate-loaded Asp105Asn and His88Gln mutants of Synechocystis sp. PCC 6803 PcyA in the initial oxidized and one-electron reduced radical states. Unlike wild-type PcyA, both mutants possess a bilin-interacting axial water molecule that is ejected from the active site upon formation of the enzyme-bound neutral radical complex. Structural studies of both mutants also show that the side chain of Glu76 is unfavorably located for D-ring vinyl reduction. On the basis of these structures and companion (15)N-(1)H long-range HMQC NMR analyses to assess the protonation state of histidine residues, we propose a new mechanistic scheme for PcyA-mediated reduction of both vinyl groups of biliverdin wherein an axial water molecule, which prematurely binds and ejects from both mutants upon one electron reduction, is required for catalytic turnover of the semireduced state.
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Affiliation(s)
- Amanda C Kohler
- Department of Chemistry, University of California, One Shields Avenue, Davis, California 95616, USA
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Biliverdin reductase is a transporter of haem into the nucleus and is essential for regulation of HO-1 gene expression by haematin. Biochem J 2008; 413:405-16. [PMID: 18412543 DOI: 10.1042/bj20080018] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
hBVR (human biliverdin reductase) is an enzyme that reduces biliverdin (the product of haem oxygenases HO-1 and HO-2 activity) to the antioxidant bilirubin. It also functions as a kinase and as a transcription factor in the MAPK (mitogen-activated protein kinase) signalling cascade. Fluorescence correlation spectroscopy was used to investigate the mobility of hBVR in living cells and its function in the nuclear transport of haematin for induction of HO-1. In transiently transfected HeLa cells only kinase-competent hBVR translocates to the nucleus. A reduced mobility in the nucleus of haematin-treated cells suggests formation of an hBVR-haematin complex and its further association with large nuclear components. The binding of haematin is specific, with the formation of a 1:1 molar complex, and the C-terminal 7-residue fragment KYCCSRK(296) of hBVR contributes to the binding. The following data suggest formation of dynamic complexes of hBVR-haematin with chromatin: (i) the reduction of hBVR mobility in the presence of haematin is greater in heterochromatic regions than in euchromatic domains and (ii) hBVR mobility is not retarded by haematin in nuclear lysates that contain only soluble factors. Moreover, hBVR kinase activity is stimulated in the presence of double-stranded DNA fragments corresponding to HO-1 antioxidant and HREs (hypoxia response elements), as well as by haematin. Experiments with nuclear localization, export signal mutants and si-hBVR [siRNA (small interfering RNA) specific to hBVR] indicate that nuclear localization of hBVR is required for induction of HO-1 by haematin. Because gene regulation is energy-dependent and haematin regulates gene expression, our data suggest that hBVR functions as an essential component of the regulatory mechanisms for haem-responsive transcriptional activation.
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Computational and experimental studies on the catalytic mechanism of biliverdin-IXbeta reductase. Biochem J 2008; 411:475-84. [PMID: 18241201 DOI: 10.1042/bj20071495] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
BVR-B (biliverdin-IXbeta reductase) also known as FR (flavin reductase) is a promiscuous enzyme catalysing the pyridine-nucleotide-dependent reduction of a variety of flavins, biliverdins, PQQ (pyrroloquinoline quinone) and ferric ion. Mechanistically it is a good model for BVR-A (biliverdin-IXalpha reductase), a potential pharmacological target for neonatal jaundice and also a potential target for adjunct therapy to maintain protective levels of biliverdin-IXalpha during organ transplantation. In a commentary on the structure of BVR-B it was noted that one outstanding issue remained: whether the mechanism was a concerted hydride transfer followed by protonation of a pyrrolic anion or protonation of the pyrrole followed by hydride transfer. In the present study we have attempted to address this question using QM/MM (quantum mechanics/molecular mechanics) calculations. QM/MM potential energy surfaces show that the lowest energy pathway proceeds with a positively charged pyrrole intermediate via two transition states. These initial calculations were performed with His(153) as the source of the proton. However site-directed mutagenesis studies with both the H153A and the H153N mutant reveal that His(153) is not required for catalytic activity. We have repeated the calculation with a solvent hydroxonium donor and obtain a similar energy landscape indicating that protonation of the pyrrole is the most likely first step followed by hydride transfer and that the required proton may come from bulk solvent. The implications of the present study for the design of inhibitors of BVR-A are discussed.
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