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Astegno A, Conter C, Bertoldi M, Dominici P. Structural Insights into the Heme Pocket and Oligomeric State of Non-Symbiotic Hemoglobins from Arabidopsis thaliana. Biomolecules 2020; 10:E1615. [PMID: 33260415 PMCID: PMC7761212 DOI: 10.3390/biom10121615] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Revised: 11/23/2020] [Accepted: 11/25/2020] [Indexed: 11/18/2022] Open
Abstract
Non-symbiotic hemoglobins AHb1 and AHb2 from Arabidopsis thaliana are hexacoordinate heme-proteins that likely have different biological roles, in view of diverse tissue localization, expression pattern, and ligand binding properties. Herein, we expand upon previous biophysical studies on these isoforms, focusing on their oligomeric states and circular dichroism (CD) characteristics. We found that AHb1 exists in solution in a concentration-dependent monomer-dimer equilibrium, while AHb2 is present only as a monomer. The quaternary structure of AHb1 affects its degree of hexacoordination with the formation of the dimer that enhances pentacoordination. Accordingly, the mutant of a conserved residue within the dimeric interface, AHb1-T45A, which is mostly monomeric in solution, has an equilibrium that is shifted toward a hexacoordinate form compared to the wild-type protein. CD studies further support differences in the globin's structure and heme moiety. The Soret CD spectra for AHb2 are opposite in sense to those for AHb1, reflecting different patterns of heme-protein side chain contacts in the two proteins. Moreover, the smaller contribution of the heme to the near-UV CD in AHb2 compared to AHb1 suggests a weaker heme-protein association in AHb2. Our data corroborate the structural diversity of AHb1 and AHb2 and confirm the leghemoglobin-like structural properties of AHb2.
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Affiliation(s)
- Alessandra Astegno
- Department of Biotechnology, University of Verona, Strada Le Grazie 15, 37134 Verona, Italy; (A.A.); (C.C.)
| | - Carolina Conter
- Department of Biotechnology, University of Verona, Strada Le Grazie 15, 37134 Verona, Italy; (A.A.); (C.C.)
| | - Mariarita Bertoldi
- Department of Neuroscience, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, Strada Le Grazie, 8, 37134 Verona, Italy;
| | - Paola Dominici
- Department of Biotechnology, University of Verona, Strada Le Grazie 15, 37134 Verona, Italy; (A.A.); (C.C.)
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Becana M, Yruela I, Sarath G, Catalán P, Hargrove MS. Plant hemoglobins: a journey from unicellular green algae to vascular plants. THE NEW PHYTOLOGIST 2020; 227:1618-1635. [PMID: 31960995 DOI: 10.1111/nph.16444] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Accepted: 12/24/2019] [Indexed: 05/17/2023]
Abstract
Globins (Glbs) are widely distributed in archaea, bacteria and eukaryotes. They can be classified into proteins with 2/2 or 3/3 α-helical folding around the heme cavity. Both types of Glbs occur in green algae, bryophytes and vascular plants. The Glbs of angiosperms have been more intensively studied, and several protein structures have been solved. They can be hexacoordinate or pentacoordinate, depending on whether a histidine is coordinating or not at the sixth position of the iron atom. The 3/3 Glbs of class 1 and the 2/2 Glbs (also called class 3 in plants) are present in all angiosperms, whereas the 3/3 Glbs of class 2 have been only found in early angiosperms and eudicots. The three Glb classes are expected to play different roles. Class 1 Glbs are involved in hypoxia responses and modulate NO concentration, which may explain their roles in plant morphogenesis, hormone signaling, cell fate determination, nutrient deficiency, nitrogen metabolism and plant-microorganism symbioses. Symbiotic Glbs derive from class 1 or class 2 Glbs and transport O2 in nodules. The physiological roles of class 2 and class 3 Glbs are poorly defined but could involve O2 and NO transport and/or metabolism, respectively. More research is warranted on these intriguing proteins to determine their non-redundant functions.
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Affiliation(s)
- Manuel Becana
- Departamento de Nutrición Vegetal, Estación Experimental de Aula Dei, Consejo Superior de Investigaciones Científicas (CSIC), Apartado 13034, 50080, Zaragoza, Spain
| | - Inmaculada Yruela
- Departamento de Nutrición Vegetal, Estación Experimental de Aula Dei, Consejo Superior de Investigaciones Científicas (CSIC), Apartado 13034, 50080, Zaragoza, Spain
- Group of Biochemistry, Biophysics and Computational Biology (BIFI-Unizar) Joint Unit to CSIC, Edificio I+D Campus Río Ebro, 50018, Zaragoza, Spain
| | - Gautam Sarath
- Wheat, Sorghum, and Forage Research Unit, USDA-ARS, East Campus, University of Nebraska-Lincoln, Lincoln, NE, 86583, USA
| | - Pilar Catalán
- Group of Biochemistry, Biophysics and Computational Biology (BIFI-Unizar) Joint Unit to CSIC, Edificio I+D Campus Río Ebro, 50018, Zaragoza, Spain
- Escuela Politécnica Superior de Huesca, Universidad de Zaragoza, 22071, Huesca, Spain
| | - Mark S Hargrove
- Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA, 50011, USA
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Distinctive structural properties of THB11, a pentacoordinate Chlamydomonas reinhardtii truncated hemoglobin with N- and C-terminal extensions. J Biol Inorg Chem 2020; 25:267-283. [PMID: 32048044 PMCID: PMC7082302 DOI: 10.1007/s00775-020-01759-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Accepted: 01/14/2020] [Indexed: 12/20/2022]
Abstract
Hemoglobins (Hbs) utilize heme b as a cofactor and are found in all kingdoms of life. The current knowledge reveals an enormous variability of Hb primary sequences, resulting in topological, biochemical and physiological individuality. As Hbs appear to modulate their reactivities through specific combinations of structural features, predicting the characteristics of a given Hb is still hardly possible. The unicellular green alga Chlamydomonas reinhardtii contains 12 genes encoding diverse Hbs of the truncated lineage, several of which possess extended N- or C-termini of unknown function. Studies on some of the Chlamydomonas Hbs revealed yet unpredictable structural and biochemical variations, which, along with a different expression of their genes, suggest diverse physiological roles. Chlamydomonas thus represents a promising system to analyze the diversification of Hb structure, biochemistry and physiology. Here, we report the crystal structure, resolved to 1.75 Å, of the heme-binding domain of cyanomet THB11 (Cre16.g662750), one of the pentacoordinate algal Hbs, which offer a free Fe-coordination site in the reduced state. The overall fold of THB11 is conserved, but individual features such as a kink in helix E, a tilted heme plane and a clustering of methionine residues at a putative tunnel exit appear to be unique. Both N- and C-termini promote the formation of oligomer mixtures, and the absence of the C terminus results in reduced nitrite reduction rates. This work widens the structural and biochemical knowledge on the 2/2Hb family and suggests that the N- and C-terminal extensions of the Chlamydomonas 2/2Hbs modulate their reactivity by intermolecular interactions.
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Mot AC, Puscas C, Miclea P, Naumova-Letia G, Dorneanu S, Podar D, Dissmeyer N, Silaghi-Dumitrescu R. Redox control and autoxidation of class 1, 2 and 3 phytoglobins from Arabidopsis thaliana. Sci Rep 2018; 8:13714. [PMID: 30209406 PMCID: PMC6135765 DOI: 10.1038/s41598-018-31922-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Accepted: 08/28/2018] [Indexed: 12/29/2022] Open
Abstract
Despite a recent increase in interest towards phytoglobins and their importance in plants, much is still unknown regarding their biochemical/biophysical properties and physiological roles. The present study presents data on three recombinant Arabidopsis phytoglobins in terms of their UV-vis and Raman spectroscopic characteristics, redox state control, redox potentials and autoxidation rates. The latter are strongly influenced by pH for all three hemoglobins - (with a fundamental involvement of the distal histidine), as well as by added anion concentrations - suggesting either a process dominated by nucleophilic displacement of superoxide for AtHb2 or an inhibitory effect for AtHb1 and AtHb3. Reducing agents, such as ascorbate and glutathione, are found to either enhance- (presumably via direct electron transfer or via allosteric regulation) or prevent autoxidation. HbFe3+ reduction was possible in the presence of high (presumably not physiologically relevant) concentrations of NADH, glutathione and ascorbate, with differing behaviors for the three globins. The iron coordination sphere is found to affect the autoxidation, redox state interconversion and redox potentials in these three phytoglobins.
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Affiliation(s)
- Augustin C Mot
- Research Center for Advanced Chemical Analysis, Instrumentation and Chemometrics, Babes-Bolyai University, 11 Arany Janos Street, RO-400028, Cluj-Napoca, Romania.
- Faculty of Chemistry and Chemical Engineering, Babes-Bolyai University, 1 Mihail Kogalniceanu Street, RO-400084, Cluj-Napoca, Romania.
- Independent Junior Research Group on Protein Recognition and Degradation, Leibniz Institute of Plant Biochemistry, Weinberg 3, D-06120, Halle (Saale), Germany.
| | - Cristina Puscas
- Faculty of Chemistry and Chemical Engineering, Babes-Bolyai University, 1 Mihail Kogalniceanu Street, RO-400084, Cluj-Napoca, Romania
| | - Patricia Miclea
- Faculty of Chemistry and Chemical Engineering, Babes-Bolyai University, 1 Mihail Kogalniceanu Street, RO-400084, Cluj-Napoca, Romania
| | - Galaba Naumova-Letia
- Faculty of Chemistry and Chemical Engineering, Babes-Bolyai University, 1 Mihail Kogalniceanu Street, RO-400084, Cluj-Napoca, Romania
| | - Sorin Dorneanu
- Faculty of Chemistry and Chemical Engineering, Babes-Bolyai University, 1 Mihail Kogalniceanu Street, RO-400084, Cluj-Napoca, Romania
| | - Dorina Podar
- Faculty of Biology and Geology, Babes-Bolyai University, 1 Mihail Kogalniceanu Street, RO-400084, Cluj-Napoca, Romania
| | - Nico Dissmeyer
- Independent Junior Research Group on Protein Recognition and Degradation, Leibniz Institute of Plant Biochemistry, Weinberg 3, D-06120, Halle (Saale), Germany
| | - Radu Silaghi-Dumitrescu
- Faculty of Chemistry and Chemical Engineering, Babes-Bolyai University, 1 Mihail Kogalniceanu Street, RO-400084, Cluj-Napoca, Romania.
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Gell DA. Structure and function of haemoglobins. Blood Cells Mol Dis 2017; 70:13-42. [PMID: 29126700 DOI: 10.1016/j.bcmd.2017.10.006] [Citation(s) in RCA: 108] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2017] [Revised: 10/29/2017] [Accepted: 10/30/2017] [Indexed: 12/18/2022]
Abstract
Haemoglobin (Hb) is widely known as the iron-containing protein in blood that is essential for O2 transport in mammals. Less widely recognised is that erythrocyte Hb belongs to a large family of Hb proteins with members distributed across all three domains of life-bacteria, archaea and eukaryotes. This review, aimed chiefly at researchers new to the field, attempts a broad overview of the diversity, and common features, in Hb structure and function. Topics include structural and functional classification of Hbs; principles of O2 binding affinity and selectivity between O2/NO/CO and other small ligands; hexacoordinate (containing bis-imidazole coordinated haem) Hbs; bacterial truncated Hbs; flavohaemoglobins; enzymatic reactions of Hbs with bioactive gases, particularly NO, and protection from nitrosative stress; and, sensor Hbs. A final section sketches the evolution of work on the structural basis for allosteric O2 binding by mammalian RBC Hb, including the development of newer kinetic models. Where possible, reference to historical works is included, in order to provide context for current advances in Hb research.
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Affiliation(s)
- David A Gell
- School of Medicine, University of Tasmania, TAS 7000, Australia.
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Mukhi N, Kundu S, Kaur J. NO dioxygenase- and peroxidase-like activity of Arabidopsis phytoglobin 3 and its role in Sclerotinia sclerotiorum defense. Nitric Oxide 2017; 68:150-162. [PMID: 28315469 DOI: 10.1016/j.niox.2017.03.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 02/17/2017] [Accepted: 03/13/2017] [Indexed: 01/05/2023]
Abstract
Phytoglobin 3 appears to be ubiquitous in plants, yet there has been dearth of evidence for their potent physiological functions. Previous crystallographic studies suggest a potential NO dioxygenase like activity of Arabidopsis phytoglobin 3 (AHb3). The present work examined the in vivo function of AHb3 in plant physiology and its role in biotic stress using Arabidopsis- Sclerotinia sclerotorium pathosystem. The gene was found to be ubiquitously expressed in all plant tissues, with moderately increased expression in roots. Its expression was induced upon NO, H2O2 and biotic stress. A C-terminal tagged GFP version of the wild type protein revealed its enhanced accumulation in the guard cells. AHb3-GFP was found to be partitioned majorly into the nucleus while residual amounts were present in the cytoplasm. The loss of function AHb3 mutant exhibited reduced root length and fresh weight. AHb3 knockout lines also displayed enhanced susceptibility towards the S. sclerotiorum. Interestingly, these lines displayed enhanced ROS accumulation upon pathogen challenge as suggested by DAB staining. Furthermore, enhanced/decreased NO accumulation in AHb3 knockout/overexpression lines upon treatment with multiple NO donors suggests a potent NO dioxygenase like activity for the protein. Taken together, our data indicate that AHb3 play a crucial role in regulating root length as well as in mediating defense response against S. sclerotiorum, possibly by modulating NO and ROS levels.
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Affiliation(s)
- Nitika Mukhi
- Department of Genetics, University of Delhi South Campus, New Delhi 110021, India
| | - Suman Kundu
- Department of Biochemistry, University of Delhi South Campus, New Delhi 110021, India
| | - Jagreet Kaur
- Department of Genetics, University of Delhi South Campus, New Delhi 110021, India.
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