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Nguyen TA, Lee C. Thr-to-Ala Mutation Leads to a Larger Aromatic Pair and Reduced Packing Density in α1,α3-Helices during Thioredoxin Cold Adaptation. ACS OMEGA 2024; 9:10812-10824. [PMID: 38463323 PMCID: PMC10918799 DOI: 10.1021/acsomega.3c09806] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Revised: 01/18/2024] [Accepted: 02/08/2024] [Indexed: 03/12/2024]
Abstract
This study investigates the impact of aromatic-aromatic interactions on the cold adaptation of thioredoxin (Trx), a small redox protein with a conserved Trx-fold structure. Two Trx orthologs, one from the psychrophilic Arctic bacterium Sphingomonas sp. (SpTrx) and the other from the mesophilic Escherichia coli (EcTrx), display distinct aromatic interactions in their α1,α3-helices. SpTrx features a larger Trp11-Phe69 pair, while EcTrx employs a smaller Phe12-Tyr70 pair along with an additional Asp9-Thr66 hydrogen bond. Smaller aromatic residues in SpTrx (Phe-Phe or Phe-Tyr pair) lead to decreased thermal and thermodynamic stabilities, increased conformational flexibility, and reduced enzyme activity. In contrast, EcTrx's thermal stability is primarily influenced by the larger Trp residue, especially in the more hydrophobic Trp-Phe pair compared to the Trp-Tyr pair. Both SpTrx and EcTrx exhibit a strengthening of the Asp-Thr hydrogen bond by a Phe-Tyr pair and a weakening by a Trp-Phe pair. Additionally, the Asp8-Thr65 hydrogen bond in SpTrx contributes to the destabilization of the Phe-Phe pair. Molecular dynamics simulations of SpTrx indicate that a smaller aromatic pair or the Asp-Thr hydrogen bond in the α1,α3-helices further destabilizes the α2-helix across the central β-sheet. Our results suggest that the Thr-to-Ala mutation destabilizes the α1,α3-helices, resulting in a larger aromatic pair and reduced packing density in psychrophilic Trxs during cold adaptation. These findings enhance our understanding of Trx's adaptation to colder temperatures.
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Affiliation(s)
- Tu Anh Nguyen
- Department of Biomedical
Science and Center for Bio-Nanomaterials, Daegu University, Gyeongsan 38453, South Korea
| | - ChangWoo Lee
- Department of Biomedical
Science and Center for Bio-Nanomaterials, Daegu University, Gyeongsan 38453, South Korea
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2
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Nguyen TT, Hoang T, Tran KN, Kim H, Jang SH, Lee C. Essential roles of buried phenylalanine in the structural stability of thioredoxin from a psychrophilic Arctic bacterium Sphingomonas sp. PLoS One 2021; 16:e0261123. [PMID: 34910731 PMCID: PMC8673628 DOI: 10.1371/journal.pone.0261123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Accepted: 11/24/2021] [Indexed: 11/21/2022] Open
Abstract
Thioredoxin (Trx), a small redox protein, exhibits thermal stability at high temperatures regardless of its origin, including psychrophiles. Trxs have a common structure consisting of the central β-sheet flanked by an aliphatic cluster on one side and an aromatic cluster on the other side. Although the roles of aromatic amino acids in the folding and stability of proteins have been studied extensively, the contributions of aromatic residues to the stability and function of Trx, particularly Trxs from cold-adapted organisms, have not been fully elucidated. This study examined the roles of aromatic amino acids in the aromatic cluster of a Trx from the psychrophilic Arctic bacterium Sphingomonas sp. PAMC 26621 (SpTrx). The aromatic cluster of SpTrx was comprised of W11, F26, F69, and F80, in which F26 at the β2 terminus was buried inside. The substitution of tyrosine for F26 changed the SpTrx conformation substantially compared to that of F69 and F80. Further biochemical and spectroscopic investigations on F26 showed that the F26Y, F26W, and F26A mutants resulted in structural instability of SpTrx in both urea- and temperature-induced unfolding and lower insulin reduction activities. The Trx reductase (SpTR) showed lower catalytic efficiencies against F26 mutants compared to the wild-type SpTrx. These results suggest that buried F26 is essential for maintaining the active-site conformation of SpTrx as an oxidoreductase and its structural stability for interactions with SpTR at colder temperatures.
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Affiliation(s)
- Thu-Thuy Nguyen
- Department of Biomedical Science and Center for Bio-Nanomaterials, Daegu University, Gyeongsan, South Korea
| | - Trang Hoang
- Department of Biomedical Science and Center for Bio-Nanomaterials, Daegu University, Gyeongsan, South Korea
| | - Kiet N. Tran
- Department of Biomedical Science and Center for Bio-Nanomaterials, Daegu University, Gyeongsan, South Korea
| | - Hyeonji Kim
- Department of Biomedical Science and Center for Bio-Nanomaterials, Daegu University, Gyeongsan, South Korea
| | - Sei-Heon Jang
- Department of Biomedical Science and Center for Bio-Nanomaterials, Daegu University, Gyeongsan, South Korea
| | - ChangWoo Lee
- Department of Biomedical Science and Center for Bio-Nanomaterials, Daegu University, Gyeongsan, South Korea
- * E-mail:
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3
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Luo G, Fujii S, Koda T, Tajima T, Sambongi Y, Hida A, Kato J. Unexpectedly high thermostability of an NADP-dependent malic enzyme from a psychrophilic bacterium, Shewanella livingstonensis Ac10. J Biosci Bioeng 2021; 132:445-450. [PMID: 34380602 DOI: 10.1016/j.jbiosc.2021.07.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Revised: 07/10/2021] [Accepted: 07/17/2021] [Indexed: 10/20/2022]
Abstract
Psychrophilic enzymes are generally active at low temperatures, and their functions have attracted much interest in food processing, biochemical research, and chemical industry. However, their activities are usually lost above their growth temperature because of their flexible and unstable structure. Here, we unexpectedly found that a homodimeric NADP-dependent malic enzyme from a psychrophilic bacterium, Shewanella livingstonensis Ac10 (SL-ME) showed sufficient activity with 60°C treatment, similar to its counterpart from mesophilic Escherichia coli (MaeB). Consistently, SL-ME and MaeB irreversibly denatured at 71.9°C and 64.5°C, respectively. Therefore, SL-ME shows robust catalytic activity, which appears to be advantageous for its application in the bioconversion of NADP to NADPH, an essential ingredient for membrane phospholipid synthesis.
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Affiliation(s)
- Gonglinfeng Luo
- Department of Molecular Biotechnology, Graduate School of Advanced Sciences of Matter, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8530, Japan
| | - Sotaro Fujii
- Unit of Food and AgriLife Science, Graduate School of Integrated Sciences for Life, Hiroshima University, 1-4-4 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8528, Japan
| | - Takumi Koda
- Unit of Biotechnology, Graduate School of Integrated Sciences for Life, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8530, Japan
| | - Takahisa Tajima
- Unit of Biotechnology, Graduate School of Integrated Sciences for Life, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8530, Japan.
| | - Yoshihiro Sambongi
- Unit of Food and AgriLife Science, Graduate School of Integrated Sciences for Life, Hiroshima University, 1-4-4 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8528, Japan
| | - Akiko Hida
- Unit of Biotechnology, Graduate School of Integrated Sciences for Life, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8530, Japan
| | - Junichi Kato
- Unit of Biotechnology, Graduate School of Integrated Sciences for Life, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8530, Japan
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4
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Borchert E, Knobloch S, Dwyer E, Flynn S, Jackson SA, Jóhannsson R, Marteinsson VT, O'Gara F, Dobson ADW. Biotechnological Potential of Cold Adapted Pseudoalteromonas spp. Isolated from 'Deep Sea' Sponges. Mar Drugs 2017. [PMID: 28629190 PMCID: PMC5484134 DOI: 10.3390/md15060184] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The marine genus Pseudoalteromonas is known for its versatile biotechnological potential with respect to the production of antimicrobials and enzymes of industrial interest. We have sequenced the genomes of three Pseudoalteromonas sp. strains isolated from different deep sea sponges on the Illumina MiSeq platform. The isolates have been screened for various industrially important enzymes and comparative genomics has been applied to investigate potential relationships between the isolates and their host organisms, while comparing them to free-living Pseudoalteromonas spp. from shallow and deep sea environments. The genomes of the sponge associated Pseudoalteromonas strains contained much lower levels of potential eukaryotic-like proteins which are known to be enriched in symbiotic sponge associated microorganisms, than might be expected for true sponge symbionts. While all the Pseudoalteromonas shared a large distinct subset of genes, nonetheless the number of unique and accessory genes is quite large and defines the pan-genome as open. Enzymatic screens indicate that a vast array of enzyme activities is expressed by the isolates, including β-galactosidase, β-glucosidase, and protease activities. A β-glucosidase gene from one of the Pseudoalteromonas isolates, strain EB27 was heterologously expressed in Escherichia coli and, following biochemical characterization, the recombinant enzyme was found to be cold-adapted, thermolabile, halotolerant, and alkaline active.
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Affiliation(s)
- Erik Borchert
- School of Microbiology, University College Cork, National University of Ireland, Cork T12 YN60, Ireland.
| | - Stephen Knobloch
- Department of Research and Innovation, Matís ohf., Reykjavik 113, Iceland.
| | - Emilie Dwyer
- School of Microbiology, University College Cork, National University of Ireland, Cork T12 YN60, Ireland.
| | - Sinéad Flynn
- School of Microbiology, University College Cork, National University of Ireland, Cork T12 YN60, Ireland.
| | - Stephen A Jackson
- School of Microbiology, University College Cork, National University of Ireland, Cork T12 YN60, Ireland.
| | - Ragnar Jóhannsson
- Department of Research and Innovation, Matís ohf., Reykjavik 113, Iceland.
| | | | - Fergal O'Gara
- School of Microbiology, University College Cork, National University of Ireland, Cork T12 YN60, Ireland.
- Biomerit Research Centre, University College Cork, National University of Ireland, Cork T12 YN60, Ireland.
- School of Biomedical Sciences, Curtin Health Innovation Research Institute, Curtin University, Perth 6102, WA, Australia.
| | - Alan D W Dobson
- School of Microbiology, University College Cork, National University of Ireland, Cork T12 YN60, Ireland.
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5
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Activity–stability relationships revisited in blue oxidases catalyzing electron transfer at extreme temperatures. Extremophiles 2016; 20:621-9. [DOI: 10.1007/s00792-016-0851-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Accepted: 05/31/2016] [Indexed: 11/26/2022]
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6
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Plaza DO, Gallardo C, Straub YD, Bravo D, Pérez-Donoso JM. Biological synthesis of fluorescent nanoparticles by cadmium and tellurite resistant Antarctic bacteria: exploring novel natural nanofactories. Microb Cell Fact 2016; 15:76. [PMID: 27154202 PMCID: PMC4858823 DOI: 10.1186/s12934-016-0477-8] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Accepted: 04/27/2016] [Indexed: 11/10/2022] Open
Abstract
Background Fluorescent nanoparticles or quantum dots (QDs) have been intensely studied for basic and applied research due to their unique size-dependent properties. There is an increasing interest in developing ecofriendly methods to synthesize these nanoparticles since they improve biocompatibility and avoid the generation of toxic byproducts. The use of biological systems, particularly prokaryotes, has emerged as a promising alternative. Recent studies indicate that QDs biosynthesis is related to factors such as cellular redox status and antioxidant defenses. Based on this, the mixture of extreme conditions of Antarctica would allow the development of natural QDs producing bacteria. Results In this study we isolated and characterized cadmium and tellurite resistant Antarctic bacteria capable of synthesizing CdS and CdTe QDs when exposed to these oxidizing heavy metals. A time dependent change in fluorescence emission color, moving from green to red, was determined on bacterial cells exposed to metals. Biosynthesis was observed in cells grown at different temperatures and high metal concentrations. Electron microscopy analysis of treated cells revealed nanometric electron-dense elements and structures resembling membrane vesicles mostly associated to periplasmic space. Purified biosynthesized QDs displayed broad absorption and emission spectra characteristic of biogenic Cd nanoparticles. Conclusions Our work presents a novel and simple biological approach to produce QDs at room temperature by using heavy metal resistant Antarctic bacteria, highlighting the unique properties of these microorganisms as potent natural producers of nano-scale materials and promising candidates for bioremediation purposes.
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Affiliation(s)
- D O Plaza
- BioNanotechnology and Microbiology Laboratory, Center for Bioinformatics and Integrative Biology (CBIB), Facultad de Ciencias Biológicas, Universidad Andres Bello, República # 239, Santiago, Chile.,Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Sergio Livingstone Pohlhammer # 1007, Santiago, Chile
| | - C Gallardo
- BioNanotechnology and Microbiology Laboratory, Center for Bioinformatics and Integrative Biology (CBIB), Facultad de Ciencias Biológicas, Universidad Andres Bello, República # 239, Santiago, Chile
| | - Y D Straub
- BioNanotechnology and Microbiology Laboratory, Center for Bioinformatics and Integrative Biology (CBIB), Facultad de Ciencias Biológicas, Universidad Andres Bello, República # 239, Santiago, Chile
| | - D Bravo
- Laboratorio de Microbiología Oral, Facultad de Odontología, Universidad de Chile, Sergio Livingstone Pohlhammer # 943, Santiago, Chile
| | - J M Pérez-Donoso
- BioNanotechnology and Microbiology Laboratory, Center for Bioinformatics and Integrative Biology (CBIB), Facultad de Ciencias Biológicas, Universidad Andres Bello, República # 239, Santiago, Chile.
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Albino A, De Angelis A, Rullo R, Maranta C, Capasso A, Ruocco MR, Sica F, De Vendittis E. The cold way for glutathione biosynthesis in the psychrophile Pseudoalteromonas haloplanktis. Redundancy and reaction rates. RSC Adv 2016. [DOI: 10.1039/c6ra15706h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In the psychrophileP. haloplanktisGSH is formed in two consecutive steps coupled to ATP hydrolysis. Differently from other sources, two redundant γ-glutamyl cysteine ligases catalyse first step; overall GSH biosynthesis is rate-limited by second step.
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Affiliation(s)
- Antonella Albino
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche
- Università di Napoli Federico II
- 80131 Napoli
- Italy
| | - Amalia De Angelis
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche
- Università di Napoli Federico II
- 80131 Napoli
- Italy
| | - Rosario Rullo
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche
- Università di Napoli Federico II
- 80131 Napoli
- Italy
- Istituto per il Sistema Produzione Animale in Ambiente Mediterraneo
| | - Chiara Maranta
- Dipartimento di Scienze Chimiche
- Università di Napoli Federico II
- Complesso Universitario di Monte Sant'Angelo
- 80126 Napoli
- Italy
| | - Alessandra Capasso
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche
- Università di Napoli Federico II
- 80131 Napoli
- Italy
| | - Maria Rosaria Ruocco
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche
- Università di Napoli Federico II
- 80131 Napoli
- Italy
| | - Filomena Sica
- Dipartimento di Scienze Chimiche
- Università di Napoli Federico II
- Complesso Universitario di Monte Sant'Angelo
- 80126 Napoli
- Italy
| | - Emmanuele De Vendittis
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche
- Università di Napoli Federico II
- 80131 Napoli
- Italy
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8
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The cold-adapted γ-glutamyl-cysteine ligase from the psychrophile Pseudoalteromonas haloplanktis. Biochimie 2014; 104:50-60. [DOI: 10.1016/j.biochi.2014.05.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Accepted: 05/09/2014] [Indexed: 01/22/2023]
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9
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Marco S, Rullo R, Albino A, Masullo M, De Vendittis E, Amato M. The thioredoxin system in the dental caries pathogen Streptococcus mutans and the food-industry bacterium Streptococcus thermophilus. Biochimie 2013; 95:2145-56. [PMID: 23954859 DOI: 10.1016/j.biochi.2013.08.008] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2013] [Accepted: 08/04/2013] [Indexed: 11/18/2022]
Abstract
The Streptococcus genus includes the pathogenic species Streptococcus mutans, the main responsible of dental caries, and the safe microorganism Streptococcus thermophilus, used for the manufacture of dairy products. These facultative anaerobes control the levels of reactive oxygen species (ROS) and indeed, both S. mutans and S. thermophilus possess a cambialistic superoxide dismutase, the key enzyme for a preventive action against ROS. To evaluate the properties of a crucial mechanism for repairing ROS damages, the molecular and functional characterization of the thioredoxin system in these streptococci was investigated. The putative genes encoding its protein components in S. mutans and S. thermophilus were analysed and the corresponding recombinant proteins were purified. A single thioredoxin reductase was obtained from either S. mutans (SmTrxB) or S. thermophilus (StTrxB1), whereas two thioredoxins were prepared from either S. mutans (SmTrxA and SmTrxH1) or S. thermophilus (StTrxA1 and StTrxA2). Both SmTrxB and StTrxB1 reduced the synthetic substrate DTNB in the presence of NADPH, whereas only SmTrxA and StTrxA1 accelerated the insulin reduction in the presence of DTT. To reconstitute an in vitro streptococcal thioredoxin system, the combined activity of the thioredoxin components was tested through the insulin precipitation in the absence of DTT. The assay functions with a combination of SmTrxB or StTrxB1 with either SmTrxA or StTrxA1. These results suggest that the streptococcal members of the thioredoxin system display a direct functional interaction between them and that these protein components are interchangeable within the Streptococcus genus. In conclusion, our data prove the existence of a functioning thioredoxin system even in these microaerophiles.
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Affiliation(s)
- Salvatore Marco
- Dipartimento di Medicina molecolare e Biotecnologie mediche, Università di Napoli Federico II, Via S. Pansini 5, 80131 Napoli, Italy
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Roman EA, Faraj SE, Cousido-Siah A, Mitschler A, Podjarny A, Santos J. Frataxin from Psychromonas ingrahamii as a model to study stability modulation within the CyaY protein family. BIOCHIMICA ET BIOPHYSICA ACTA 2013; 1834:1168-80. [PMID: 23429177 DOI: 10.1016/j.bbapap.2013.02.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Revised: 01/26/2013] [Accepted: 02/11/2013] [Indexed: 10/27/2022]
Abstract
Adaptation of life to low temperatures influences both protein stability and flexibility. Thus, proteins from psychrophilic organisms are excellent models to study relations between these properties. Here we focused on frataxin from Psychromonas ingrahamii (pFXN), an extreme psychrophilic sea ice bacterium that can grow at temperatures as low as -12°C. This α/β protein is highly conserved and plays a key role in iron homeostasis as an iron chaperone. In contrast to other frataxin homologs, chemical and temperature unfolding experiments showed that the thermodynamic stability of pFXN is strongly modulated by pHs: ranging from 5.5±0.9 (pH6.0) to 0.9±0.3kcalmol(-1) (pH8.0). This protein was crystallized and its X-ray structure solved at 1.45Å. Comparison of B-factor profiles between Escherichia coli and P. ingrahamii frataxin variants (51% of identity) suggests that, although both proteins share the same structural features, their flexibility distribution is different. Molecular dynamics simulations showed that protonation of His44 or His67 in pFXN lowers the mobility of regions encompassing residues 20-30 and the C-terminal end, probably through favorable electrostatic interactions with residues Asp27, Glu42 and Glu99. Since the C-terminal end of the protein is critical for the stabilization of the frataxin fold, the predictions presented may be reporting on the microscopic origin of the decrease in global stability produced near neutral pH in the psychrophilic variant. We propose that suboptimal electrostatic interactions may have been an evolutionary strategy for the adaptation of frataxin flexibility and function to cold environments.
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Affiliation(s)
- Ernesto A Roman
- Instituto de Química y Fisicoquímica Biológicas, Universidad de Buenos Aires, Buenos Aires, Argentina
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11
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Feller G. Psychrophilic enzymes: from folding to function and biotechnology. SCIENTIFICA 2013; 2013:512840. [PMID: 24278781 PMCID: PMC3820357 DOI: 10.1155/2013/512840] [Citation(s) in RCA: 163] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2012] [Accepted: 11/06/2012] [Indexed: 05/10/2023]
Abstract
Psychrophiles thriving permanently at near-zero temperatures synthesize cold-active enzymes to sustain their cell cycle. Genome sequences, proteomic, and transcriptomic studies suggest various adaptive features to maintain adequate translation and proper protein folding under cold conditions. Most psychrophilic enzymes optimize a high activity at low temperature at the expense of substrate affinity, therefore reducing the free energy barrier of the transition state. Furthermore, a weak temperature dependence of activity ensures moderate reduction of the catalytic activity in the cold. In these naturally evolved enzymes, the optimization to low temperature activity is reached via destabilization of the structures bearing the active site or by destabilization of the whole molecule. This involves a reduction in the number and strength of all types of weak interactions or the disappearance of stability factors, resulting in improved dynamics of active site residues in the cold. These enzymes are already used in many biotechnological applications requiring high activity at mild temperatures or fast heat-inactivation rate. Several open questions in the field are also highlighted.
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Affiliation(s)
- Georges Feller
- Laboratory of Biochemistry, Centre for Protein Engineering, Institute of Chemistry, University of Liège, B6a, 4000 Liège, Belgium
- *Georges Feller:
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Optimization to low temperature activity in psychrophilic enzymes. Int J Mol Sci 2012; 13:11643-11665. [PMID: 23109875 PMCID: PMC3472767 DOI: 10.3390/ijms130911643] [Citation(s) in RCA: 143] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2012] [Revised: 09/07/2012] [Accepted: 09/10/2012] [Indexed: 01/20/2023] Open
Abstract
Psychrophiles, i.e., organisms thriving permanently at near-zero temperatures, synthesize cold-active enzymes to sustain their cell cycle. These enzymes are already used in many biotechnological applications requiring high activity at mild temperatures or fast heat-inactivation rate. Most psychrophilic enzymes optimize a high activity at low temperature at the expense of substrate affinity, therefore reducing the free energy barrier of the transition state. Furthermore, a weak temperature dependence of activity ensures moderate reduction of the catalytic activity in the cold. In these naturally evolved enzymes, the optimization to low temperature activity is reached via destabilization of the structures bearing the active site or by destabilization of the whole molecule. This involves a reduction in the number and strength of all types of weak interactions or the disappearance of stability factors, resulting in improved dynamics of active site residues in the cold. Considering the subtle structural adjustments required for low temperature activity, directed evolution appears to be the most suitable methodology to engineer cold activity in biological catalysts.
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13
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Albino A, Marco S, Di Maro A, Chambery A, Masullo M, De Vendittis E. Characterization of a cold-adapted glutathione synthetase from the psychrophile Pseudoalteromonas haloplanktis. MOLECULAR BIOSYSTEMS 2012; 8:2405-14. [PMID: 22777241 DOI: 10.1039/c2mb25116g] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Glutathione (GSH) biosynthesis occurs through two ATP-dependent reactions, usually involving distinct enzymes; in the second step of this process, catalysed by glutathione synthetase (GshB), GSH is formed from γ-glutamylcysteine and glycine. A recombinant form of GshB from the cold-adapted source Pseudoalteromonas haloplanktis (rPhGshB) was purified and characterised. The enzyme formed a disulfide adduct with β-mercaptoethanol, when purified in the presence of this reducing agent. The homotetrameric form of rPhGshB observed at high protein concentration disassembled into two homodimers at low concentration. A new method for directly determining the rPhGshB activity was developed, based on [γ-(32)P]ATP hydrolysis coupled to the GSH synthesis. The ATPase activity required the presence of both γ-glutamylcysteine and glycine and its optimum was reached in the 7.4-8.6 pH range; a divalent cation was absolutely required for the activity, whereas monovalent cations were dispensable. rPhGshB was active at low temperatures and had a similar affinity for ATP (K(m) 0.26 mM) and γ-glutamylcysteine (K(m) 0.25 mM); a lower affinity was measured for glycine (K(m) 0.75 mM). The oxidised form of glutathione (GSSG) acted as an irreversible inhibitor of rPhGshB (K(i) 10.7 mM) and formed disulfide adducts with the enzyme. rPhGshB displayed a great temperature-dependent increase in its activity with an unusually high value of energy of activation (75 kJ mol(-1)) for a psychrophilic enzyme. The enzyme was moderately thermostable, its half inactivation temperature being 50.5 °C after 10 min exposure. The energy of activation of the heat inactivation process was 208 kJ mol(-1). To our knowledge, this is the first contribution to the characterization of a GshB from cold-adapted sources.
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Affiliation(s)
- Antonella Albino
- Dipartimento di Biochimica e Biotecnologie Mediche, Università di Napoli Federico II, Via S. Pansini 5, 80131 Napoli, Italy
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