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Functional Characterization and Structural Analysis of NADH Oxidase Mutants from Thermus thermophilus HB27: Role of Residues 166, 174, and 194 in the Catalytic Properties and Thermostability. Microorganisms 2019; 7:microorganisms7110515. [PMID: 31683638 PMCID: PMC6921046 DOI: 10.3390/microorganisms7110515] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Revised: 10/25/2019] [Accepted: 10/28/2019] [Indexed: 11/16/2022] Open
Abstract
The Thermus thermophilus strain HB27 NADH-oxidase (Tt27-NOX) catalyzes the oxidation of nicotinamide adenine dinucleotide (NAD(P)H) by reducing molecular oxygen to hydrogen peroxide in a two-electron transfer mechanism. Surprisingly, Tt27-NOX showed significant differences in catalytic properties compared to its counterpart from the strain HB8 (Tt8-NOX), despite a high degree of sequence homology between both variants. The sequence comparison between both enzymes revealed only three divergent amino acid residues at positions 166, 174, and 194. Motivated with these findings, in this work we performed mutagenesis experiments in the former three positions to study the specific role of these residues in the catalytic properties and thermostability of Tt27-NOX. We subjected five mutants, along with the wild-type enzyme, to biochemical characterization and thermal stability studies. As a result, we identified two more active and more thermostable variants than any Tt8-NOX variant reported in the literature. The most active and thermostable variant K166/H174/Y194 retained 90% of its initial activity after 5 h at pH 7 and 80 °C and an increase in melting temperature of 48.3 °C compared with the least active variant K166/R174/Y194 (inactivated after 15 min of incubation). These results, supported by structural analysis and molecular dynamics simulation studies, suggest that Lys at position 166 may stabilize the loop in which His174 is located, increasing thermal stability.
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Structural study reveals the temperature-dependent conformational flexibility of Tk-PTP, a protein tyrosine phosphatase from Thermococcus kodakaraensis KOD1. PLoS One 2018; 13:e0197635. [PMID: 29791483 PMCID: PMC5965843 DOI: 10.1371/journal.pone.0197635] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Accepted: 05/05/2018] [Indexed: 11/19/2022] Open
Abstract
Protein tyrosine phosphatases (PTPs) originating from eukaryotes or bacteria have been under intensive structural and biochemical investigation, whereas archaeal PTP proteins have not been investigated extensively; therefore, they are poorly understood. Here, we present the crystal structures of Tk-PTP derived from the hyperthermophilic archaeon Thermococcus kodakaraensis KOD1, in both the active and inactive forms. Tk-PTP adopts a common dual-specificity phosphatase (DUSP) fold, but it undergoes an atypical temperature-dependent conformational change in its P-loop and α4−α5 loop regions, switching between the inactive and active forms. Through comprehensive analyses of Tk-PTP, including additional structural determination of the G95A mutant form, enzymatic activity assays, and structural comparison with the other archaeal PTP, it was revealed that the presence of the GG motif in the P-loop is necessary but not sufficient for the structural flexibility of Tk-PTP. It was also proven that Tk-PTP contains dual general acid/base residues unlike most of the other DUSP proteins, and that both the residues are critical in its phosphatase activity. This work provides the basis for expanding our understanding of the previously uncharacterized PTP proteins from archaea, the third domain of living organisms.
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Miletti T, Di Trani J, Jr Levros LC, Mittermaier A. Conformational plasticity surrounding the active site of NADH oxidase from Thermus thermophilus. Protein Sci 2015; 24:1114-28. [PMID: 25970557 PMCID: PMC4500311 DOI: 10.1002/pro.2693] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Accepted: 04/26/2015] [Indexed: 11/08/2022]
Abstract
Biotechnological applications of enzymes can involve the use of these molecules under nonphysiological conditions. Thus, it is of interest to understand how environmental variables affect protein structure and dynamics and how this ultimately modulates enzyme function. NADH oxidase (NOX) from Thermus thermophilus exemplifies how enzyme activity can be tuned by reaction conditions, such as temperature, cofactor substitution, and the addition of cosolutes. This enzyme catalyzes the oxidation of reduced NAD(P)H to NAD(P)(+) with the concurrent reduction of O2 to H2O2, with relevance to biosensing applications. It is thermophilic, with an optimum temperature of approximately 65°C and sevenfold lower activity at 25°C. Moderate concentrations (≈1M) of urea and other chaotropes increase NOX activity by up to a factor of 2.5 at room temperature. Furthermore, it is a flavoprotein that accepts either FMN or the much larger FAD as cofactor. We have used nuclear magnetic resonance (NMR) titration and (15)N spin relaxation experiments together with isothermal titration calorimetry to study how NOX structure and dynamics are affected by changes in temperature, the addition of urea and the substitution of the FMN cofactor with FAD. The majority of signals from NOX are quite insensitive to changes in temperature, cosolute addition, and cofactor substitution. However, a small cluster of residues surrounding the active site shows significant changes. These residues are implicated in coupling changes in the solution conditions of the enzyme to changes in catalytic activity.
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Affiliation(s)
- Teresa Miletti
- Department of Chemistry, McGill UniversityMontreal, Quebec, H3A 0B8
| | - Justin Di Trani
- Department of Chemistry, McGill UniversityMontreal, Quebec, H3A 0B8
| | - Louis-Charles Jr Levros
- Laboratoire de biologie moléculaire, Département des Sciences Biologiques, Centre BioMed, Université du Québec à MontréalMontréal, Québec, H3C 3P8
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Medvedev KE, Alemasov NA, Vorobjev YN, Boldyreva EV, Kolchanov NA, Afonnikov DA. Molecular dynamics simulations of the Nip7 proteins from the marine deep- and shallow-water Pyrococcus species. BMC STRUCTURAL BIOLOGY 2014; 14:23. [PMID: 25315147 PMCID: PMC4209456 DOI: 10.1186/s12900-014-0023-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/06/2014] [Accepted: 10/03/2014] [Indexed: 11/13/2022]
Abstract
Background The identification of the mechanisms of adaptation of protein structures to extreme environmental conditions is a challenging task of structural biology. We performed molecular dynamics (MD) simulations of the Nip7 protein involved in RNA processing from the shallow-water (P. furiosus) and the deep-water (P. abyssi) marine hyperthermophylic archaea at different temperatures (300 and 373 K) and pressures (0.1, 50 and 100 MPa). The aim was to disclose similarities and differences between the deep- and shallow-sea protein models at different temperatures and pressures. Results The current results demonstrate that the 3D models of the two proteins at all the examined values of pressures and temperatures are compact, stable and similar to the known crystal structure of the P. abyssi Nip7. The structural deviations and fluctuations in the polypeptide chain during the MD simulations were the most pronounced in the loop regions, their magnitude being larger for the C-terminal domain in both proteins. A number of highly mobile segments the protein globule presumably involved in protein-protein interactions were identified. Regions of the polypeptide chain with significant difference in conformational dynamics between the deep- and shallow-water proteins were identified. Conclusions The results of our analysis demonstrated that in the examined ranges of temperatures and pressures, increase in temperature has a stronger effect on change in the dynamic properties of the protein globule than the increase in pressure. The conformational changes of both the deep- and shallow-sea protein models under increasing temperature and pressure are non-uniform. Our current results indicate that amino acid substitutions between shallow- and deep-water proteins only slightly affect overall stability of two proteins. Rather, they may affect the interactions of the Nip7 protein with its protein or RNA partners.
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Affiliation(s)
- Kirill E Medvedev
- Institute of Cytology and Genetics SB RAS, Prospekt Lavrentyeva 10, Novosibirsk, 630090, Russia.
| | - Nikolay A Alemasov
- Institute of Cytology and Genetics SB RAS, Prospekt Lavrentyeva 10, Novosibirsk, 630090, Russia.
| | - Yuri N Vorobjev
- Institute of Chemical Biology and Fundamental Medicine SB RAS, Prospekt Lavrentyeva 8, Novosibirsk, 630090, Russia.
| | - Elena V Boldyreva
- Novosibirsk State University, Pirogova str. 2, Novosibirsk, 630090, Russia. .,Institute of Solid Chemistry and Mechanochemistry, SB RAS, Novosibirsk, 630090, Russia.
| | - Nikolay A Kolchanov
- Institute of Cytology and Genetics SB RAS, Prospekt Lavrentyeva 10, Novosibirsk, 630090, Russia. .,Novosibirsk State University, Pirogova str. 2, Novosibirsk, 630090, Russia. .,NRC Kurchatov Institute, 1, Akademika Kurchatova pl., Moscow, 123182, Russia.
| | - Dmitry A Afonnikov
- Institute of Cytology and Genetics SB RAS, Prospekt Lavrentyeva 10, Novosibirsk, 630090, Russia. .,Novosibirsk State University, Pirogova str. 2, Novosibirsk, 630090, Russia.
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