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Wang F, Ma X, Sun Y, Guo E, Shi C, Yuan Z, Li Y, Li Q, Lu F, Liu Y. Structure-Guided Engineering of a Protease to Improve Its Activity under Cold Conditions. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2023; 71:12528-12537. [PMID: 37561891 DOI: 10.1021/acs.jafc.3c02338] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/12/2023]
Abstract
Bacillus proteases commonly exhibit remarkably reduced activity under cold conditions. Herein, we employed a tailored combination of a loop engineering strategy and iterative saturation mutagenesis method to engineer two loops for substrate binding at the entrance of the substrate tunnel of a protease (bcPRO) from Bacillus clausii to improve its activity under cold conditions. The variant MT6 (G95P/A96D/S99W/S101T/P127S/S126T) exhibited an 18.3-fold greater catalytic efficiency than the wild-type (WT) variant at 10 °C. Molecular dynamics simulations and dynamic tunnel analysis indicated that the introduced mutations extended the substrate-binding pocket volume and facilitated extra interactions with the substrate, promoting catalysis through binding in a more favorable conformation. This study provides insights and strategies relevant to improving the activities of proteases and supplies a novel protease with enhanced activity under cold conditions for the food industry to maintain the initial flavor and color of food and reduce energy consumption.
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Affiliation(s)
- Fenghua Wang
- Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education, Tianjin Key Laboratory of Industrial Microbiology, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, P. R. China
| | - Xiangyang Ma
- Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education, Tianjin Key Laboratory of Industrial Microbiology, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, P. R. China
| | - Ying Sun
- Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education, Tianjin Key Laboratory of Industrial Microbiology, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, P. R. China
| | - Enping Guo
- Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education, Tianjin Key Laboratory of Industrial Microbiology, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, P. R. China
| | - Chaoshuo Shi
- Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education, Tianjin Key Laboratory of Industrial Microbiology, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, P. R. China
| | - Zhaoting Yuan
- Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education, Tianjin Key Laboratory of Industrial Microbiology, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, P. R. China
| | - Yu Li
- Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education, Tianjin Key Laboratory of Industrial Microbiology, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, P. R. China
| | - Qinggang Li
- Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education, Tianjin Key Laboratory of Industrial Microbiology, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, P. R. China
| | - Fuping Lu
- Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education, Tianjin Key Laboratory of Industrial Microbiology, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, P. R. China
| | - Yihan Liu
- Key Laboratory of Industrial Fermentation Microbiology, Ministry of Education, Tianjin Key Laboratory of Industrial Microbiology, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, P. R. China
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Sora V, Tiberti M, Beltrame L, Dogan D, Robbani SM, Rubin J, Papaleo E. PyInteraph2 and PyInKnife2 to Analyze Networks in Protein Structural Ensembles. J Chem Inf Model 2023; 63:4237-4245. [PMID: 37437128 DOI: 10.1021/acs.jcim.3c00574] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/14/2023]
Abstract
Due to the complex nature of noncovalent interactions and their long-range effects, analyzing protein conformations using network theory can be enlightening. Protein Structure Networks (PSNs) provide a convenient formalism to study protein structures in relation to essential properties such as key residues for structural stability, allosteric communication, and the effects of modifications of the protein. PSNs can be defined according to very different principles, and the available tools have limitations in input formats, supported models, and version control. Other outstanding problems are related to the definition of network cutoffs and the assessment of the stability of the network properties. The protein science community could benefit from a common framework to carry out these analyses and make them easier to reproduce, reuse, and evaluate. We here provide two open-source software packages, PyInteraph2 and PyInKnife2, to implement and analyze PSNs in a reproducible and documented manner. PyInteraph2 interfaces with multiple formats for protein ensembles and incorporates different network models with the possibility of integrating them into a macronetwork and performing various downstream analyses, including hubs, connected components, and several other centrality measures, and visualizes the networks or further analyzes them thanks to compatibility with Cytoscape.PyInKnife2 that supports the network models implemented in PyInteraph2. It employs a jackknife resampling approach to estimate the convergence of network properties and streamline the selection of distance cutoffs. We foresee that the modular structure of the code and the supported version control system will promote the transition to a community-driven effort, boost reproducibility, and establish common protocols in the PSN field. As developers, we will guarantee the introduction of new functionalities and maintenance, assistance, and training of new contributors.
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Affiliation(s)
- Valentina Sora
- Cancer Structural Biology, Danish Cancer Institute, Strandboulevarden 49, 2100 Copenhagen, Denmark
- Cancer Systems Biology, Section of Bioinformatics, Department of Health and Technology, Technical University of Denmark, 2800 Lyngby, Denmark
| | - Matteo Tiberti
- Cancer Structural Biology, Danish Cancer Institute, Strandboulevarden 49, 2100 Copenhagen, Denmark
| | - Ludovica Beltrame
- Cancer Systems Biology, Section of Bioinformatics, Department of Health and Technology, Technical University of Denmark, 2800 Lyngby, Denmark
| | - Deniz Dogan
- Cancer Structural Biology, Danish Cancer Institute, Strandboulevarden 49, 2100 Copenhagen, Denmark
| | - Shahriyar Mahdi Robbani
- Cancer Structural Biology, Danish Cancer Institute, Strandboulevarden 49, 2100 Copenhagen, Denmark
| | - Joshua Rubin
- Cancer Structural Biology, Danish Cancer Institute, Strandboulevarden 49, 2100 Copenhagen, Denmark
| | - Elena Papaleo
- Cancer Structural Biology, Danish Cancer Institute, Strandboulevarden 49, 2100 Copenhagen, Denmark
- Cancer Systems Biology, Section of Bioinformatics, Department of Health and Technology, Technical University of Denmark, 2800 Lyngby, Denmark
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3
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Rhinehardt K, Dong M. Computational analysis of protein conformational heterogeneity. J Biomol Struct Dyn 2022; 40:12100-12105. [PMID: 34424141 DOI: 10.1080/07391102.2021.1967784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
In this paper, we applied the molecular dynamics (MD) simulations and used thermolysin as the system to study the overall protein dynamics and side chain dihedral angles across the Arrhenius break. Simulations were performed at a high temperature of 36 °C which is above the previously observed Arrhenius break, and the lower temperature of 20 °C which is below the Arrhenius break. We observed different protein dynamics and conformational heterogeneity of side chain dihedral angles of thermolysin at the two temperatures. Our results indicated that certain regions of thermolysin have a higher level of fluctuation at lower temperature. A temperature dependent dihedral angles were also observed at the two temperatures. The changes observed in the protein indicated key areas of temperature sensitivity within the protein.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Kristen Rhinehardt
- Department of Computational Data Science and Engineering, North Carolina Agricultural and Technical State University, Greensboro, NC, USA
| | - Ming Dong
- Department of Chemistry, North Carolina Agricultural and Technical State University, Greensboro, NC, USA
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Masnoddin M, Ling CMWV, Yusof NA. Functional Analysis of Conserved Hypothetical Proteins from the Antarctic Bacterium, Pedobacter cryoconitis Strain BG5 Reveals Protein Cold Adaptation and Thermal Tolerance Strategies. Microorganisms 2022; 10:microorganisms10081654. [PMID: 36014072 PMCID: PMC9415557 DOI: 10.3390/microorganisms10081654] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Revised: 08/04/2022] [Accepted: 08/12/2022] [Indexed: 11/16/2022] Open
Abstract
Pedobacter cryoconitis BG5 is an obligate psychrophilic bacterium that was first isolated on King George Island, Antarctica. Over the last 50 years, the West Antarctic, including King George Island, has been one of the most rapidly warming places on Earth, hence making it an excellent area to measure the resilience of living species in warmed areas exposed to the constantly changing environment due to climate change. This bacterium encodes a genome of approximately 5694 protein-coding genes. However, 35% of the gene models for this species are found to be hypothetical proteins (HP). In this study, three conserved HP genes of P. cryoconitis, designated pcbg5hp1, pcbg5hp2 and pcbg5hp12, were cloned and the proteins were expressed, purified and their functions and structures were evaluated. Real-time quantitative PCR analysis revealed that these genes were expressed constitutively, suggesting a potentially important role where the expression of these genes under an almost constant demand might have some regulatory functions in thermal stress tolerance. Functional analysis showed that these proteins maintained their activities at low and moderate temperatures. Meanwhile, a low citrate synthase aggregation at 43 °C in the presence of PCBG5HP1 suggested the characteristics of chaperone activity. Furthermore, our comparative structural analysis demonstrated that the HPs exhibited cold-adapted traits, most notably increased flexibility in their 3D structures compared to their counterparts. Concurrently, the presence of a disulphide bridge and aromatic clusters was attributed to PCBG5HP1’s unusual protein stability and chaperone activity. Thus, this suggested that the HPs examined in this study acquired strategies to maintain a balance between molecular stability and structural flexibility. Conclusively, this study has established the structure–function relationships of the HPs produced by P. cryoconitis and provided crucial experimental evidence indicating their importance in thermal stress response.
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Affiliation(s)
- Makdi Masnoddin
- Biotechnology Research Institute, Universiti Malaysia Sabah, Jalan UMS, Kota Kinabalu 88400, Sabah, Malaysia
- Preparatory Centre for Science and Technology, Universiti Malaysia Sabah, Jalan UMS, Kota Kinabalu 88400, Sabah, Malaysia
| | | | - Nur Athirah Yusof
- Biotechnology Research Institute, Universiti Malaysia Sabah, Jalan UMS, Kota Kinabalu 88400, Sabah, Malaysia
- Correspondence:
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5
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Cold-active enzymes in the dairy industry: Insight into cold adaption mechanisms and their applications. Trends Food Sci Technol 2022. [DOI: 10.1016/j.tifs.2022.05.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Extracellular Enzymatic Activities of Oceanic Pelagic Fungal Strains and the Influence of Temperature. J Fungi (Basel) 2022; 8:jof8060571. [PMID: 35736054 PMCID: PMC9225461 DOI: 10.3390/jof8060571] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Revised: 05/23/2022] [Accepted: 05/23/2022] [Indexed: 11/20/2022] Open
Abstract
Although terrestrial and aquatic fungi are well-known decomposers of organic matter, the role of marine fungi remains largely unknown. Recent studies based on omics suggest that marine fungi potentially play a major role in elemental cycles. However, there is very limited information on the diversity of extracellular enzymatic activities performed by pelagic fungi in the ocean and how these might be affected by community composition and/or critical environmental parameters such as temperature. In order to obtain information on the potential metabolic activity of marine fungi, extracellular enzymatic activities (EEA) were investigated. Five marine fungal species belonging to the most abundant pelagic phyla (Ascomycota and Basidiomycota) were grown at 5 °C and 20 °C, and fluorogenic enzymatic assays were performed using six substrate analogues for the hydrolysis of carbohydrates (β-glucosidase, β-xylosidase, and N-acetyl-β-D-glucosaminidase), amino acids (leucine aminopeptidase), and of organic phosphorus (alkaline phosphatase) and sulfur compounds (sulfatase). Remarkably, all fungal strains were capable of hydrolyzing all the offered substrates. However, the hydrolysis rate (Vmax) and half-saturation constant (Km) varied among the fungal strains depending on the enzyme type. Temperature had a strong impact on the EEAs, resulting in Q10 values of up to 6.1 and was species and substrate dependent. The observed impact of temperature on fungal EEA suggests that warming of the global ocean might alter the contribution of pelagic fungi in marine biogeochemical cycles.
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Garcia Gonzalez J, Hernandez FJ. Nuclease activity: an exploitable biomarker in bacterial infections. Expert Rev Mol Diagn 2022; 22:265-294. [PMID: 35240900 DOI: 10.1080/14737159.2022.2049249] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
INTRODUCTION In the increasingly challenging field of clinical microbiology, diagnosis is a cornerstone whose accuracy and timing are crucial for the successful management, therapy, and outcome of infectious diseases. Currently employed biomarkers of infectious diseases define the scope and limitations of diagnostic techniques. As such, expanding the biomarker catalog is crucial to address unmet needs and bring about novel diagnostic functionalities and applications. AREAS COVERED This review describes the extracellular nucleases of 15 relevant bacterial pathogens and discusses the potential use of nuclease activity as a diagnostic biomarker. Articles were searched for in PubMed using terms: "nuclease", "bacteria", "nuclease activity" or "biomarker". For overview sections, original and review articles between 2000 and 2019 were searched for using terms: "infections", "diagnosis", "bacterial", "burden", "challenges". Informative articles were selected. EXPERT OPINION Using the catalytic activity of nucleases offers new possibilities compared to established biomarkers. Nucleic acid activatable reporters in combination with different transduction platforms and delivery methods can be used to detect disease-associated nuclease activity patterns in vitro and in vivo for prognostic and diagnostic applications. Even when these patterns are not obvious or of unknown etiology, screening platforms could be used to identify new disease reporters.
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Affiliation(s)
- Javier Garcia Gonzalez
- Department of Physics, Chemistry and Biology, Linköping University, Linköping, Sweden.,Wallenberg Centre for Molecular Medicine (WCMM), Linköping, Sweden.,Nucleic Acids Technologies Laboratory (NAT-lab), Linköping University, Linköping, Sweden
| | - Frank J Hernandez
- Department of Physics, Chemistry and Biology, Linköping University, Linköping, Sweden.,Wallenberg Centre for Molecular Medicine (WCMM), Linköping, Sweden.,Nucleic Acids Technologies Laboratory (NAT-lab), Linköping University, Linköping, Sweden
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Yusof NA, Hashim NHF, Bharudin I. Cold Adaptation Strategies and the Potential of Psychrophilic Enzymes from the Antarctic Yeast, Glaciozyma antarctica PI12. J Fungi (Basel) 2021; 7:jof7070528. [PMID: 34209103 PMCID: PMC8306469 DOI: 10.3390/jof7070528] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Revised: 06/19/2021] [Accepted: 06/25/2021] [Indexed: 12/20/2022] Open
Abstract
Psychrophilic organisms possess several adaptive strategies which allow them to sustain life at low temperatures between −20 to 20 °C. Studies on Antarctic psychrophiles are interesting due to the multiple stressors that exist on the permanently cold continent. These organisms produce, among other peculiarities, cold-active enzymes which not only have tremendous biotechnological potential but are valuable models for fundamental research into protein structure and function. Recent innovations in omics technologies such as genomics, transcriptomics, proteomics and metabolomics have contributed a remarkable perspective of the molecular basis underpinning the mechanisms of cold adaptation. This review critically discusses similar and different strategies of cold adaptation in the obligate psychrophilic yeast, Glaciozyma antarctica PI12 at the molecular (genome structure, proteins and enzymes, gene expression) and physiological (antifreeze proteins, membrane fluidity, stress-related proteins) levels. Our extensive studies on G. antarctica have revealed significant insights towards the innate capacity of- and the adaptation strategies employed by this psychrophilic yeast for life in the persistent cold. Furthermore, several cold-active enzymes and proteins with biotechnological potential are also discussed.
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Affiliation(s)
- Nur Athirah Yusof
- Biotechnology Research Institute, Universiti Malaysia Sabah, Jalan UMS, Kota Kinabalu 88400, Sabah, Malaysia;
| | - Noor Haza Fazlin Hashim
- Water Quality Laboratory, National Water Research Institute Malaysia (NAHRIM), Ministry of Environment and Water, Jalan Putra Permai, Seri Kembangan 43300, Selangor, Malaysia;
| | - Izwan Bharudin
- Department of Biological Sciences and Biotechnology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Bangi 43600, Selangor, Malaysia
- Correspondence:
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9
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Dong M. A Minireview on Temperature Dependent Protein Conformational Sampling. Protein J 2021; 40:545-553. [PMID: 34181188 DOI: 10.1007/s10930-021-10012-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/19/2021] [Indexed: 12/01/2022]
Abstract
In this minireview we discuss the role of the more subtle conformational change-protein conformational sampling and connect it to the classic relationship of protein structure and function. The theory of pre-existing functional states of protein are discussed in context of alternate protein conformational sampling. Last, we discuss how temperature, ligand binding and mutations affect the protein conformational sampling mode which is linked to the protein function regulation. The review includes several protein systems that showed temperature dependent protein conformational sampling. We also specifically included two enzyme systems, thermophilic alcohol dehydrogenase (ht-ADH) and thermolysin which we previously studied when discussing temperature dependent protein conformational sampling.
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Affiliation(s)
- Ming Dong
- Department of Chemistry, North Carolina Agricultural and Technical State University, 1601 E Market Street, Greensboro, NC, 27410, USA.
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Characterization of SdGA, a cold-adapted glucoamylase from Saccharophagus degradans. ACTA ACUST UNITED AC 2021; 30:e00625. [PMID: 34041001 PMCID: PMC8141877 DOI: 10.1016/j.btre.2021.e00625] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Revised: 04/24/2021] [Accepted: 04/28/2021] [Indexed: 11/24/2022]
Abstract
We investigated the structural and functional properties of SdGA, a glucoamylase (GA) from Saccharophagus degradans, a marine bacterium which degrades different complex polysaccharides at high rate. SdGA is composed mainly by a N-terminal GH15_N domain linked to a C-terminal catalytic domain (CD) found in the GH15 family of glycosylhydrolases with an overall structure similar to other bacterial GAs. The protein was expressed in Escherichia coli cells, purified and its biochemical properties were investigated. Although SdGA has a maximum activity at 39 °C and pH 6.0, it also shows high activity in a wide range, from low to mild temperatures, like cold-adapted enzymes. Furthermore, SdGA has a higher content of flexible residues and a larger CD due to various amino acid insertions compared to other thermostable GAs. We propose that this novel SdGA, is a cold-adapted enzyme that might be suitable for use in different industrial processes that require enzymes which act at low or medium temperatures.
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Zhang ZB, Xia YL, Dong GH, Fu YX, Liu SQ. Exploring the Cold-Adaptation Mechanism of Serine Hydroxymethyltransferase by Comparative Molecular Dynamics Simulations. Int J Mol Sci 2021; 22:1781. [PMID: 33670090 PMCID: PMC7916883 DOI: 10.3390/ijms22041781] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2021] [Revised: 02/08/2021] [Accepted: 02/08/2021] [Indexed: 12/20/2022] Open
Abstract
Cold-adapted enzymes feature a lower thermostability and higher catalytic activity compared to their warm-active homologues, which are considered as a consequence of increased flexibility of their molecular structures. The complexity of the (thermo)stability-flexibility-activity relationship makes it difficult to define the strategies and formulate a general theory for enzyme cold adaptation. Here, the psychrophilic serine hydroxymethyltransferase (pSHMT) from Psychromonas ingrahamii and its mesophilic counterpart, mSHMT from Escherichia coli, were subjected to μs-scale multiple-replica molecular dynamics (MD) simulations to explore the cold-adaptation mechanism of the dimeric SHMT. The comparative analyses of MD trajectories reveal that pSHMT exhibits larger structural fluctuations and inter-monomer positional movements, a higher global flexibility, and considerably enhanced local flexibility involving the surface loops and active sites. The largest-amplitude motion mode of pSHMT describes the trends of inter-monomer dissociation and enlargement of the active-site cavity, whereas that of mSHMT characterizes the opposite trends. Based on the comparison of the calculated structural parameters and constructed free energy landscapes (FELs) between the two enzymes, we discuss in-depth the physicochemical principles underlying the stability-flexibility-activity relationships and conclude that (i) pSHMT adopts the global-flexibility mechanism to adapt to the cold environment and, (ii) optimizing the protein-solvent interactions and loosening the inter-monomer association are the main strategies for pSHMT to enhance its flexibility.
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Affiliation(s)
- Zhi-Bi Zhang
- State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan & School of Life Sciences, Yunnan University, Kunming 650091, China; (Z.-B.Z.); (Y.-L.X.); (G.-H.D.)
- Yunnan Key Laboratory of Stem Cell and Regenerative Medicine & Biomedical Engineering Research Center, Kunming Medical University, Kunming 650500, China
| | - Yuan-Ling Xia
- State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan & School of Life Sciences, Yunnan University, Kunming 650091, China; (Z.-B.Z.); (Y.-L.X.); (G.-H.D.)
| | - Guang-Heng Dong
- State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan & School of Life Sciences, Yunnan University, Kunming 650091, China; (Z.-B.Z.); (Y.-L.X.); (G.-H.D.)
| | - Yun-Xin Fu
- State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan & School of Life Sciences, Yunnan University, Kunming 650091, China; (Z.-B.Z.); (Y.-L.X.); (G.-H.D.)
- Human Genetics Center and Division of Biostatistics, School of Public Health, The University of Texas Health Science Center, Houston, TX 77030, USA
| | - Shu-Qun Liu
- State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan & School of Life Sciences, Yunnan University, Kunming 650091, China; (Z.-B.Z.); (Y.-L.X.); (G.-H.D.)
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Hjörleifsson JG, Helland R, Magnúsdóttir M, Ásgeirsson B. The high catalytic rate of the cold-active Vibrio alkaline phosphatase requires a hydrogen bonding network involving a large interface loop. FEBS Open Bio 2020; 11:173-184. [PMID: 33197282 PMCID: PMC7780099 DOI: 10.1002/2211-5463.13041] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 11/11/2020] [Accepted: 11/13/2020] [Indexed: 11/24/2022] Open
Abstract
The role of surface loops in mediating communication through residue networks is still a relatively poorly understood part in the study of cold adaptation of enzymes, especially in terms of their quaternary interactions. Alkaline phosphatase (AP) from the psychrophilic marine bacterium Vibrio splendidus (VAP) is characterized by an analogous large surface loop in each monomer, referred to as the large loop, that hovers over the active site of the other monomer. It presumably has a role in the high catalytic efficiency of VAP which accompanies its extremely low thermal stability. Here, we designed several different variants of VAP with the aim of removing intersubunit interactions at the dimer interface. Breaking the intersubunit contacts from one residue in particular (Arg336) reduced the temperature stability of the catalytically potent conformation and caused a 40% drop in catalytic rate. The high catalytic rates of enzymes from cold‐adapted organisms are often associated with increased dynamic flexibility. Comparison of the relative B‐factors of the R336L crystal structure to that of the wild‐type confirmed surface flexibility was increased in a loop on the opposite monomer, but not in the large loop. The increase in flexibility resulted in a reduced catalytic rate. The large loop increases the area of the interface between the subunits through its contacts and may facilitate an alternating structural cycle demanded by a half‐of‐sites reaction mechanism through stronger ties, as the dimer oscillates between high affinity (active) or low phosphoryl group affinity (inactive).
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Affiliation(s)
| | - Ronny Helland
- Department of Chemistry, Faculty of Science and Technology, The Norwegian Structural Biology Centre (NorStruct), UiT, The Arctic University of Tromsø, Norway
| | - Manuela Magnúsdóttir
- Department of Biochemistry, Science Institute, University of Iceland, Reykjavik, Iceland
| | - Bjarni Ásgeirsson
- Department of Biochemistry, Science Institute, University of Iceland, Reykjavik, Iceland
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Lambrughi M, Sanader Maršić Ž, Saez-Jimenez V, Mapelli V, Olsson L, Papaleo E. Conformational gating in ammonia lyases. Biochim Biophys Acta Gen Subj 2020; 1864:129605. [PMID: 32222547 DOI: 10.1016/j.bbagen.2020.129605] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Revised: 03/11/2020] [Accepted: 03/23/2020] [Indexed: 11/17/2022]
Abstract
BACKGROUND Ammonia lyases are enzymes of industrial and biomedical interest. Knowledge of structure-dynamics-function relationship in ammonia lyases is instrumental for exploiting the potential of these enzymes in industrial or biomedical applications. METHODS We investigated the conformational changes in the proximity of the catalytic pocket of a 3-methylaspartate ammonia lyase (MAL) as a model system. At this scope, we used microsecond all-atom molecular dynamics simulations, analyzed with dimensionality reduction techniques, as well as in terms of contact networks and correlated motions. RESULTS We identify two regulatory elements in the MAL structure, i.e., the β5-α2 loop and the helix-hairpin-loop subdomain. These regulatory elements undergo conformational changes switching from 'occluded' to 'open' states. The rearrangements are coupled to changes in the accessibility of the active site. The β5-α2 loop and the helix-hairpin-loop subdomain modulate the formation of tunnels from the protein surface to the catalytic site, making the active site more accessible to the substrate when they are in an open state. CONCLUSIONS Our work pinpoints a sequential mechanism, in which the helix-hairpin-loop subdomain of MAL needs to break a subset of intramolecular interactions first to favor the displacement of the β5-α2 loop. The coupled conformational changes of these two elements contribute to modulate the accessibility of the catalytic site. GENERAL SIGNIFICANCE Similar molecular mechanisms can have broad relevance in other ammonia lyases with similar regulatory loops. Our results also imply that it is important to account for protein dynamics in the design of variants of ammonia lyases for industrial and biomedical applications.
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Affiliation(s)
- Matteo Lambrughi
- Computational Biology Laboratory, Danish Cancer Society Research Center, Copenhagen, Denmark
| | - Željka Sanader Maršić
- Computational Biology Laboratory, Danish Cancer Society Research Center, Copenhagen, Denmark
| | - Veronica Saez-Jimenez
- Division of Industrial Biotechnology, Department of Biology and Biological Engineering, Chalmers University of Technology, Göteborg, Sweden
| | - Valeria Mapelli
- Division of Industrial Biotechnology, Department of Biology and Biological Engineering, Chalmers University of Technology, Göteborg, Sweden
| | - Lisbeth Olsson
- Division of Industrial Biotechnology, Department of Biology and Biological Engineering, Chalmers University of Technology, Göteborg, Sweden
| | - Elena Papaleo
- Computational Biology Laboratory, Danish Cancer Society Research Center, Copenhagen, Denmark; Translational Disease Systems Biology, Faculty of Health and Medical Sciences, Novo Nordisk Foundation Center for Protein Research University of Copenhagen, Copenhagen, Denmark.
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14
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Sočan J, Isaksen GV, Brandsdal BO, Åqvist J. Towards Rational Computational Engineering of Psychrophilic Enzymes. Sci Rep 2019; 9:19147. [PMID: 31844096 PMCID: PMC6915740 DOI: 10.1038/s41598-019-55697-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Accepted: 11/30/2019] [Indexed: 12/14/2022] Open
Abstract
Cold-adapted enzymes from psychrophilic species achieve their high catalytic efficiency at low temperature by a different partitioning of the activation free energy into its enthalpic and entropic components, compared to orthologous mesophilic enzymes. Their lower activation enthalpy, partly compensated by an increased entropic penalty, has been suggested to originate from changes in flexibility of the protein surface. Multiple sequence alignments of psychrophilic and mesophilic enzymes also show characteristic motifs located in surface loops of the protein. Here, we use computer simulations to examine the effects of a number of designed surface mutations of psychrophilic and mesophilic elastases on the temperature dependence of the catalyzed peptide cleavage reaction. For each of 14 mutant enzyme variants we report calculations of their thermodynamic activation parameters. The results show that substitution of psychrophilic loop residues into the mesophilic enzyme consistently changes both the activation parameters and loop flexibilities towards the former, and vice versa for opposite substitutions.
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Affiliation(s)
- Jaka Sočan
- Department of Cell and Molecular Biology, Uppsala University, Biomedical Center, Box 596, SE-751 24, Uppsala, Sweden
| | - Geir Villy Isaksen
- Hylleraas Centre for Quantum Molecular Sciences, Department of Chemistry, UiT - The Arctic University of Norway, N9037, Tromsø, Norway
| | - Bjørn Olav Brandsdal
- Hylleraas Centre for Quantum Molecular Sciences, Department of Chemistry, UiT - The Arctic University of Norway, N9037, Tromsø, Norway
| | - Johan Åqvist
- Department of Cell and Molecular Biology, Uppsala University, Biomedical Center, Box 596, SE-751 24, Uppsala, Sweden. .,Hylleraas Centre for Quantum Molecular Sciences, Department of Chemistry, UiT - The Arctic University of Norway, N9037, Tromsø, Norway.
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Structural features of cold-adapted dimeric GH2 β-D-galactosidase from Arthrobacter sp. 32cB. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2019; 1867:776-786. [PMID: 31195142 DOI: 10.1016/j.bbapap.2019.06.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2019] [Revised: 05/12/2019] [Accepted: 06/06/2019] [Indexed: 12/21/2022]
Abstract
Crystal structures of cold-adapted β-d-galactosidase (EC 3.2.1.23) from the Antarctic bacterium Arthrobacter sp. 32cB (ArthβDG) have been determined in an unliganded form resulting from diffraction experiments conducted at 100 K (at resolution 1.8 Å) and at room temperature (at resolution 3.0 Å). A detailed comparison of those two structures of the same enzyme was performed in order to estimate differences in their molecular flexibility and rigidity and to study structural rationalization for the cold-adaptation of the investigated enzyme. Furthermore, a comparative analysis with structures of homologous enzymes from psychrophilic, mesophilic, and thermophilic sources has been discussed to elucidate the relationship between structure and cold-adaptation in a wider context. The performed studies confirm that the structure of cold-adapted ArthβDG maintains balance between molecular stability and structural flexibility, which can be observed independently on the temperature of conducted X-ray diffraction experiments. Obtained information about proper protein function under given conditions provide a guideline for rational engineering of proteins in terms of their temperature optimum and thermal stability.
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Liang Z, Verkhivker GM, Hu G. Integration of network models and evolutionary analysis into high-throughput modeling of protein dynamics and allosteric regulation: theory, tools and applications. Brief Bioinform 2019; 21:815-835. [DOI: 10.1093/bib/bbz029] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 02/04/2019] [Accepted: 02/21/2019] [Indexed: 12/24/2022] Open
Abstract
Abstract
Proteins are dynamical entities that undergo a plethora of conformational changes, accomplishing their biological functions. Molecular dynamics simulation and normal mode analysis methods have become the gold standard for studying protein dynamics, analyzing molecular mechanism and allosteric regulation of biological systems. The enormous amount of the ensemble-based experimental and computational data on protein structure and dynamics has presented a major challenge for the high-throughput modeling of protein regulation and molecular mechanisms. In parallel, bioinformatics and systems biology approaches including genomic analysis, coevolution and network-based modeling have provided an array of powerful tools that complemented and enriched biophysical insights by enabling high-throughput analysis of biological data and dissection of global molecular signatures underlying mechanisms of protein function and interactions in the cellular environment. These developments have provided a powerful interdisciplinary framework for quantifying the relationships between protein dynamics and allosteric regulation, allowing for high-throughput modeling and engineering of molecular mechanisms. Here, we review fundamental advances in protein dynamics, network theory and coevolutionary analysis that have provided foundation for rapidly growing computational tools for modeling of allosteric regulation. We discuss recent developments in these interdisciplinary areas bridging computational biophysics and network biology, focusing on promising applications in allosteric regulations, including the investigation of allosteric communication pathways, protein–DNA/RNA interactions and disease mutations in genomic medicine. We conclude by formulating and discussing future directions and potential challenges facing quantitative computational investigations of allosteric regulatory mechanisms in protein systems.
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Affiliation(s)
- Zhongjie Liang
- School of Biology and Basic Medical Sciences, Soochow University, Suzhou, China
| | - Gennady M Verkhivker
- Department of Computational and Data Sciences, Schmid College of Science and Technology, Chapman University, Orange, CA, USA
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, USA
| | - Guang Hu
- School of Biology and Basic Medical Sciences, Soochow University, Suzhou, China
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New Nuclease from Extremely Psychrophilic Microorganism Psychromonas ingrahamii 37: Identification and Characterization. Mol Biotechnol 2018; 61:122-133. [PMID: 30539415 DOI: 10.1007/s12033-018-0142-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Nucleases are an important group of hydrolases that degrade nucleic acids, with broad spectrum of applications in science and industry. In this paper, we report the identification and characterization of the nuclease from extremely psychrophilic bacterium Psychromonas ingrahamii that grows exponentially at 5 °C, but may also grow at even lower temperatures (down to - 12 °C). The putative endonuclease I gene, identified in the genome of P. ingrahamii, was cloned and expressed in Pichia pastoris. The recombinant protein was purified and its nucleolytic features were studied. The new enzyme, named by us as PinNuc, displays the features characteristic for the nonselective endonucleases, and has the ability to degrade different forms of nucleic acids. It is very active at room temperature in low ion-strength buffer and in the presence of low concentrations of magnesium ions. The enzyme, which possesses six cysteine residues, the most likely all engaged in disulphide bridges, is active only in oxidized form, and can be efficiently inactivated by the addition of low amounts of a reducing agent. According to our knowledge, it is the first nuclease, belonging to endonuclease I family, isolated from such extremely psychrophilic organism.
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Zeng J, Huang Z. From Levinthal's Paradox to the Effects of Cell Environmental Perturbation on Protein Folding. Curr Med Chem 2018; 26:7537-7554. [PMID: 30332937 DOI: 10.2174/0929867325666181017160857] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 07/04/2018] [Accepted: 08/03/2018] [Indexed: 01/01/2023]
Abstract
BACKGROUND The rapidly increasing number of known protein sequences calls for more efficient methods to predict the Three-Dimensional (3D) structures of proteins, thus providing basic knowledge for rational drug design. Understanding the folding mechanism of proteins is valuable for predicting their 3D structures and for designing proteins with new functions and medicinal applications. Levinthal's paradox is that although the astronomical number of conformations possible even for proteins as small as 100 residues cannot be fully sampled, proteins in nature normally fold into the native state within timescales ranging from microseconds to hours. These conflicting results reveal that there are factors in organisms that can assist in protein folding. METHODS In this paper, we selected a crowded cell-like environment and temperature, and the top three Posttranslational Modifications (PTMs) as examples to show that Levinthal's paradox does not reflect the folding mechanism of proteins. We then revealed the effects of these factors on protein folding. RESULTS The results summarized in this review indicate that a crowded cell-like environment, temperature, and the top three PTMs reshape the Free Energy Landscapes (FELs) of proteins, thereby regulating the folding process. The balance between entropy and enthalpy is the key to understanding the effect of the crowded cell-like environment and PTMs on protein folding. In addition, the stability/flexibility of proteins is regulated by temperature. CONCLUSION This paper concludes that the cellular environment could directly intervene in protein folding. The long-term interactions of the cellular environment and sequence evolution may enable proteins to fold efficiently. Therefore, to correctly understand the folding mechanism of proteins, the effect of the cellular environment on protein folding should be considered.
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Affiliation(s)
- Juan Zeng
- Guangdong Provincial Key Laboratory of Medical Molecular Diagnostics, Dongguan Scientific Research Center, Guangdong Medical University, Dongguan, Guangdong 523808, China.,Laboratory of Computational Chemistry and Drug Design, Laboratory of Chemical Genomics, Peking University Shenzhen Graduate School, Shenzhen 518055, China
| | - Zunnan Huang
- Guangdong Provincial Key Laboratory of Medical Molecular Diagnostics, Dongguan Scientific Research Center, Guangdong Medical University, Dongguan, Guangdong 523808, China
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Wang Y, Hou Y, Wang Y, Zheng L, Xu X, Pan K, Li R, Wang Q. A Novel Cold-Adapted Leucine Dehydrogenase from Antarctic Sea-Ice Bacterium Pseudoalteromonas sp. ANT178. Mar Drugs 2018; 16:md16100359. [PMID: 30275355 PMCID: PMC6213480 DOI: 10.3390/md16100359] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Revised: 09/27/2018] [Accepted: 09/27/2018] [Indexed: 02/06/2023] Open
Abstract
l-tert-leucine and its derivatives are useful as pharmaceutical active ingredients, in which leucine dehydrogenase (LeuDH) is the key enzyme in their enzymatic conversions. In the present study, a novel cold-adapted LeuDH, psleudh, was cloned from psychrotrophic bacteria Pseudoalteromonas sp. ANT178, which was isolated from Antarctic sea-ice. Bioinformatics analysis of the gene psleudh showed that the gene was 1209 bp in length and coded for a 42.6 kDa protein containing 402 amino acids. PsLeuDH had conserved Phe binding site and NAD+ binding site, and belonged to a member of the Glu/Leu/Phe/Val dehydrogenase family. Homology modeling analysis results suggested that PsLeuDH exhibited more glycine residues, reduced proline residues, and arginine residues, which might be responsible for its catalytic efficiency at low temperature. The recombinant PsLeuDH (rPsLeuDH) was purified a major band with the high specific activity of 275.13 U/mg using a Ni-NTA affinity chromatography. The optimum temperature and pH for rPsLeuDH activity were 30 °C and pH 9.0, respectively. Importantly, rPsLeuDH retained at least 40% of its maximum activity even at 0 °C. Moreover, the activity of rPsLeuDH was the highest in the presence of 2.0 M NaCl. Substrate specificity and kinetic studies of rPsLeuDH demonstrated that l-leucine was the most suitable substrate, and the catalytic activity at low temperatures was ensured by maintaining a high kcat value. The results of the current study would provide insight into Antarctic sea-ice bacterium LeuDH, and the unique properties of rPsLeuDH make it a promising candidate as a biocatalyst in medical and pharmaceutical industries.
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Affiliation(s)
- Yatong Wang
- School of Marine Science and Technology, Harbin Institute of Technology, Weihai 264209, China.
| | - Yanhua Hou
- School of Marine Science and Technology, Harbin Institute of Technology, Weihai 264209, China.
| | - Yifan Wang
- School of Marine Science and Technology, Harbin Institute of Technology, Weihai 264209, China.
| | - Lu Zheng
- School of Marine Science and Technology, Harbin Institute of Technology, Weihai 264209, China.
| | - Xianlei Xu
- School of Marine Science and Technology, Harbin Institute of Technology, Weihai 264209, China.
| | - Kang Pan
- School of Marine Science and Technology, Harbin Institute of Technology, Weihai 264209, China.
| | - Rongqi Li
- School of Marine Science and Technology, Harbin Institute of Technology, Weihai 264209, China.
| | - Quanfu Wang
- School of Marine Science and Technology, Harbin Institute of Technology, Weihai 264209, China.
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Next generation industrial biotechnology based on extremophilic bacteria. Curr Opin Biotechnol 2018; 50:94-100. [DOI: 10.1016/j.copbio.2017.11.016] [Citation(s) in RCA: 186] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Revised: 11/24/2017] [Accepted: 11/27/2017] [Indexed: 01/13/2023]
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Brininger C, Spradlin S, Cobani L, Evilia C. The more adaptive to change, the more likely you are to survive: Protein adaptation in extremophiles. Semin Cell Dev Biol 2018; 84:158-169. [PMID: 29288800 DOI: 10.1016/j.semcdb.2017.12.016] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Revised: 12/25/2017] [Accepted: 12/25/2017] [Indexed: 12/22/2022]
Abstract
Discovering how organisms and their proteins adapt to extreme conditions is a complicated process. Every condition has its own set of adaptations that make it uniquely stable in its environment. The purpose of our review is to discuss what is known in the extremophilic community about protein adaptations. To simplify our mission, we broke the extremophiles into three broad categories: thermophiles, halophiles and psychrophiles. While there are crossover organisms- organisms that exist in two or more extremes, like heat plus acid or cold plus pressure, most of them have a primary adaptation that is within one of these categories which tends to be the most easily identifiable one. While the generally known adaptations are still accepted, like thermophilic proteins have increased ionic interactions and a hardier hydrophobic core, halophilic proteins have a large increase in acidic amino acids and amino acid/peptide insertions and psychrophiles have a much more open structure and reduced ionic interactions, some new information has come to light. Thermophilic stability can be improved by increased subunit-subunit or subunit-cofactor interactions. Halophilic proteins have reversible folding when in the presence of salt. Psychrophilic proteins have an increase in cavities that not only decrease the formation of ice, but also increase flexibility under low temperature conditions. In a proof of concept experiment, we applied what is currently known about adaptations to a well characterized protein, malate dehydrogenase (MDH). While this protein has been profiled in the literature, we are applying our adaptation predictions to its sequence and structure to see if the described adaptations apply. Our analysis demonstrates that thermophilic and halophilic adaptations fit the corresponding MDHs very well. However, because the number of psychrophiles MDH sequences and structures is low, our analysis on psychrophiles is inconclusive and needs more information. By discussing known extremophilic adaptations and applying them to a random, conserved protein, we have found that general adaptations are conserved and can be predicted in proposed extremophilic proteins. The present field of extremophile adaptations is discovering more and more ways organisms and their proteins have adapted. The more that is learned about protein adaptation, the closer we get to custom proteins, designed to fit any extreme and solve some of the world's most pressing environmental problems.
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Affiliation(s)
- C Brininger
- Department of Chemistry, Idaho State University, Pocatello, ID 83209, USA
| | - S Spradlin
- Department of Chemistry, Idaho State University, Pocatello, ID 83209, USA
| | - L Cobani
- Department of Chemistry, Idaho State University, Pocatello, ID 83209, USA
| | - C Evilia
- Department of Chemistry, Idaho State University, Pocatello, ID 83209, USA.
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Lund BA, Thomassen AM, Carlsen TJO, Leiros HKS. Structure, activity and thermostability investigations of OXA-163, OXA-181 and OXA-245 using biochemical analysis, crystal structures and differential scanning calorimetry analysis. Acta Crystallogr F Struct Biol Commun 2017; 73:579-587. [PMID: 28994407 PMCID: PMC5633926 DOI: 10.1107/s2053230x17013838] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Accepted: 09/25/2017] [Indexed: 01/20/2023] Open
Abstract
The first crystal structures of the class D β-lactamases OXA-181 and OXA-245 were determined to 2.05 and 2.20 Å resolution, respectively; in addition, the structure of a new crystal form of OXA-163 was resolved to 2.07 Å resolution. All of these enzymes are OXA-48-like and have been isolated from different clinical Klebsiella pneumoniae strains and also from other human pathogens such as Pseudomonas aeruginosa and Escherichia coli. Here, enzyme kinetics and thermostability studies are presented, and the new crystal structures are used to explain the observed variations. OXA-245 had the highest melting point (Tm = 55.8°C), as determined by differential scanning calorimetry, compared with OXA-163 (Tm = 49.4°C) and OXA-181 (Tm = 52.6°C). The differences could be explained by the loss of two salt bridges in OXA-163, and an overall decrease in the polarity of the surface of OXA-181 compared with OXA-245.
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Affiliation(s)
- Bjarte Aarmo Lund
- Department of Chemistry, UiT The Arctic University of Norway, 9037 Tromsø, Norway
| | - Ane Molden Thomassen
- Department of Chemistry, UiT The Arctic University of Norway, 9037 Tromsø, Norway
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