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Luo X, Al-Antaki AHM, Harvey DP, Ruan Y, He S, Zhang W, Raston CL. Vortex Fluidic Mediated Synthesis of Macroporous Bovine Serum Albumin-Based Microspheres. ACS APPLIED MATERIALS & INTERFACES 2018; 10:27224-27232. [PMID: 30028117 DOI: 10.1021/acsami.8b09316] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Macroporous bovine serum albumin (BSA) nanoparticles with controllable diameter were readily fabricated in a rapidly rotating angled glass tube in a vortex fluidic device (VFD). Systematically varying the rotational speed and the ratio of BSA, ethanol, and glutaraldehyde led to conditions for generating ca. 600 nm diameter macroporous particles that have intrinsic fluorescence emission at 520 nm when excited at 490 nm. The presence of the macropores increased the absorption efficiency of rhodamine B with potential applications for drug delivery purpose, compared with BSA nanoparticles having surfaces devoid of pores. Further control over the size of BSA nanoparticles occurred in the presence of C-phycocyanin protein during the VFD processing, along with control of their shape, from spheres to pockets, as established in exploring the parameter space of the microfluidic device.
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Affiliation(s)
| | | | | | - Yinlan Ruan
- ARC Centre of Excellence for Nanoscale BioPhotonics, Institute of Photonics and Advanced Sensing , Adelaide University , Adelaide , South Australia 5005 , Australia
| | - Shan He
- Department of Food Science and Engineering, School of Chemistry Chemical Engineering , Guangzhou University , Guangzhou 510006 , China
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2
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A novel “trifunctional protease” with reducibility, hydrolysis, and localization used for wool anti-felting treatment. Appl Microbiol Biotechnol 2018; 102:9159-9170. [DOI: 10.1007/s00253-018-9276-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2018] [Revised: 06/27/2018] [Accepted: 07/25/2018] [Indexed: 12/31/2022]
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3
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El-Maiss J, Cuccarese M, Maerten C, Lupattelli P, Chiummiento L, Funicello M, Schaaf P, Jierry L, Boulmedais F. Mussel-Inspired Electro-Cross-Linking of Enzymes for the Development of Biosensors. ACS APPLIED MATERIALS & INTERFACES 2018; 10:18574-18584. [PMID: 29799715 DOI: 10.1021/acsami.8b04764] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
In medical diagnosis and environmental monitoring, enzymatic biosensors are widely applied because of their high sensitivity, potential selectivity, and their possibility of miniaturization/automation. Enzyme immobilization is a critical process in the development of this type of biosensors with the necessity to avoid the denaturation of the enzymes and ensuring their accessibility toward the analyte. Electrodeposition of macromolecules is increasingly considered to be the most suitable method for the design of biosensors. Being simple and attractive, it finely controls the immobilization of enzymes on electrode surfaces, usually by entrapment or adsorption, using an electrical stimulus. Performed manually, enzyme immobilization by cross-linking prevents enzyme leaching and was never done using an electrochemical stimulus. In this work, we present a mussel-inspired electro-cross-linking process using glucose oxidase (GOX) and a homobifunctionalized catechol ethylene oxide spacer as a cross-linker in the presence of ferrocene methanol (FC) acting as a mediator of the buildup. Performed in one pot, the process takes place in three steps: (i) electro-oxidation of FC, by the application of cyclic voltammetry, creating a gradient of ferrocenium (FC+); (ii) oxidation of bis-catechol into a bis-quinone molecule by reaction with the electrogenerated FC+; and (iii) a chemical reaction of bis-quinone with free amino moieties of GOX through Michael addition and a Schiff's base condensation reaction. Employed for the design of a second-generation glucose biosensor using ferrocene methanol (FC) as a mediator, this new enzyme immobilization process presents several advantages. The cross-linked enzymatic film (i) is obtained in a one-pot process with nonmodified GOX, (ii) is strongly linked to the metallic electrode surface thanks to catechol moieties, and (iii) presents no leakage issues. The developed GOX/bis-catechol film shows a good response to glucose with a quite wide linear range from 1.0 to 12.5 mM as well as a good sensitivity (0.66 μA/mM cm2) and a high selectivity to glucose. These films would distinguish between healthy (3.8 and 6.5 mM) and hyperglycemic subjects (>7 mM). Finally, we show that this electro-cross-linking process allows the development of miniaturized biosensors through the functionalization of a single electrode out of a microelectrode array. Elegant and versatile, this electro-cross-linking process can also be used for the development of enzymatic biofuel cells.
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Affiliation(s)
- Janwa El-Maiss
- Université de Strasbourg, CNRS, Institut Charles Sadron UPR 22 , 67034 Strasbourg , France
| | - Marco Cuccarese
- Université de Strasbourg, CNRS, Institut Charles Sadron UPR 22 , 67034 Strasbourg , France
- Dipartimento di Scienze , Università degli Studi della Basilicata , 85100 Potenza , Italy
| | - Clément Maerten
- Université de Strasbourg, CNRS, Institut Charles Sadron UPR 22 , 67034 Strasbourg , France
| | - Paolo Lupattelli
- Université de Strasbourg, CNRS, Institut Charles Sadron UPR 22 , 67034 Strasbourg , France
- Dipartimento di Scienze , Università degli Studi della Basilicata , 85100 Potenza , Italy
| | - Lucia Chiummiento
- Dipartimento di Scienze , Università degli Studi della Basilicata , 85100 Potenza , Italy
| | - Maria Funicello
- Dipartimento di Scienze , Università degli Studi della Basilicata , 85100 Potenza , Italy
| | - Pierre Schaaf
- Université de Strasbourg, CNRS, Institut Charles Sadron UPR 22 , 67034 Strasbourg , France
- Ecole de Chimie, Polymères et Matériaux , Université de Strasbourg , 67087 Strasbourg , France
- University of Strasbourg Institute of Advanced Study , 67083 Strasbourg , France
- Biomatériaux et Bioingénierie , Institut National de la Santé et de la Recherche Médicale, UMR-S 1121 , 67087 Strasbourg , France
- Faculté de Chirurgie Dentaire, Fédération de Médecine Translationnelle de Strasbourg (FMTS), and Fédération des Matériaux et Nanoscience d'Alsace (FMNA) , Université de Strasbourg , 67000 Strasbourg , France
- International Center for Frontier Research in Chemistry , 67083 Strasbourg , France
| | - Loïc Jierry
- Université de Strasbourg, CNRS, Institut Charles Sadron UPR 22 , 67034 Strasbourg , France
- Ecole de Chimie, Polymères et Matériaux , Université de Strasbourg , 67087 Strasbourg , France
| | - Fouzia Boulmedais
- Université de Strasbourg, CNRS, Institut Charles Sadron UPR 22 , 67034 Strasbourg , France
- University of Strasbourg Institute of Advanced Study , 67083 Strasbourg , France
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Bekasova OD, Borzova VA, Shubin VV, Kovalyov LI, Stein-Margolina VA, Kurganov BI. An increase in the resistance of R-phycoerythrin to thermal aggregation by silver nanoparticles synthesized in nanochannels of the pigment. APPL BIOCHEM MICRO+ 2016. [DOI: 10.1134/s0003683816010026] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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5
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Dumitraşcu L, Stănciuc N, Bahrim GE, Ciumac A, Aprodu I. pH and heat-dependent behaviour of glucose oxidase down to single molecule level by combined fluorescence spectroscopy and molecular modelling. JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE 2016; 96:1906-1914. [PMID: 26058827 DOI: 10.1002/jsfa.7296] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Revised: 04/06/2015] [Accepted: 06/01/2015] [Indexed: 06/04/2023]
Abstract
BACKGROUND In the food industry, glucose oxidase (GOX) is used to improve the shelf life of food materials. The pH- and heat-induced conformational changes of glucose oxidase from Aspergillus niger were quantified by means of fluorescence spectroscopy and molecular dynamics simulations. RESULTS The phase diagram showed an all-or-none transition process, indicating that pH and temperature largely influence the conformational state of GOX. Shifts in maximum wavelength of Trp, Tyr were registered as the protein encounters a lower pH (pH 4.0), suggesting significant changes of the polarity around the chromophore molecule. Quenching experiments using KI showed higher quenching constants of Trp and flavin adenine dinucleotide upon heating or by changing pH value, and were mainly correlated with the conformational changes upon protein matrix. Finally, valuable insights into the thermal behaviour of GOX were obtained from molecular modelling results. CONCLUSIONS The conformation and structure of GOX protein is dependent upon the pH and heat treatment applied. Molecular dynamics simulation indicated significant changes in the substrate binding region at temperatures over 60 °C that might affect enzyme activity. Moreover, an important alteration of the small pocket hosting the positively charged His(516) residue responsible for oxygen activation appears evident at high temperatures.
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Affiliation(s)
- Loredana Dumitraşcu
- Dunarea de Jos University of Galati, Faculty of Food Science and Engineering, Domneascã Street 111, 800201, Galati, Romania
| | - Nicoleta Stănciuc
- Dunarea de Jos University of Galati, Faculty of Food Science and Engineering, Domneascã Street 111, 800201, Galati, Romania
| | - Gabriela Elena Bahrim
- Dunarea de Jos University of Galati, Faculty of Food Science and Engineering, Domneascã Street 111, 800201, Galati, Romania
| | - Alexandrina Ciumac
- Dunarea de Jos University of Galati, Faculty of Food Science and Engineering, Domneascã Street 111, 800201, Galati, Romania
| | - Iuliana Aprodu
- Dunarea de Jos University of Galati, Faculty of Food Science and Engineering, Domneascã Street 111, 800201, Galati, Romania
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6
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DiMauro MA, Nandi SK, Raghavan CT, Kar RK, Wang B, Bhunia A, Nagaraj RH, Biswas A. Acetylation of Gly1 and Lys2 promotes aggregation of human γD-crystallin. Biochemistry 2014; 53:7269-82. [PMID: 25393041 PMCID: PMC4245984 DOI: 10.1021/bi501004y] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
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The human lens contains three major
protein families: α-,
β-, and γ-crystallin. Among the several variants of γ-crystallin
in the human lens, γD-crystallin is a major form. γD-Crystallin
is primarily present in the nuclear region of the lens and contains
a single lysine residue at the second position (K2). In this study,
we investigated the acetylation of K2 in γD-crystallin in aging
and cataractous human lenses. Our results indicated that K2 is acetylated
at an early age and that the amount of K2-acetylated γD-crystallin
increased with age. Mass spectrometric analysis revealed that in addition
to K2, glycine 1 (G1) was acetylated in γD-crystallin from human
lenses and in γD-crystallin acetylated in vitro. The chaperone ability of α-crystallin for acetylated γD-crystallin
was lower than that for the nonacetylated protein. The tertiary structure
and the microenvironment of the cysteine residues were significantly
altered by acetylation. The acetylated protein exhibited higher surface
hydrophobicity, was unstable against thermal and chemical denaturation,
and exhibited a higher propensity to aggregate at 80 °C in comparison
to the nonacetylated protein. Acetylation enhanced the GdnHCl-induced
unfolding and slowed the subsequent refolding of γD-crystallin.
Theoretical analysis indicated that the acetylation of K2 and G1 reduced
the structural stability of the protein and brought the distal cysteine
residues (C18 and C78) into close proximity. Collectively, these results
indicate that the acetylation of G1 and K2 residues in γD-crystallin
likely induced a molten globule-like structure, predisposing it to
aggregation, which may account for the high content of aggregated
proteins in the nucleus of aged and cataractous human lenses.
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Affiliation(s)
- Michael A DiMauro
- Department of Ophthalmology and Visual Sciences and ‡Center for Proteomics and Bioinformatics, Case Western Reserve University School of Medicine , Cleveland, Ohio, United States
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7
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Eskandari K, Ghourchian H. Structural changes of glucose oxidase upon interaction with gold-coated magnetic nano-particles. Int J Biol Macromol 2012; 51:998-1002. [DOI: 10.1016/j.ijbiomac.2012.08.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2011] [Revised: 07/31/2012] [Accepted: 08/01/2012] [Indexed: 10/28/2022]
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8
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Tohidi Moghadam T, Ranjbar B, Khajeh K. Conformation and activity of lysozyme on binding to two types of gold nanorods: A comparative study. Int J Biol Macromol 2012; 51:91-6. [DOI: 10.1016/j.ijbiomac.2012.04.020] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2011] [Revised: 04/16/2012] [Accepted: 04/19/2012] [Indexed: 10/28/2022]
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9
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Cheong KW, Leow TC, Rahman RNZRA, Basri M, Rahman MBA, Salleh AB. Reductive Alkylation Causes the Formation of a Molten Globule-Like Intermediate Structure in Geobacillus zalihae Strain T1 Thermostable Lipase. Appl Biochem Biotechnol 2010; 164:362-75. [DOI: 10.1007/s12010-010-9140-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2010] [Accepted: 11/29/2010] [Indexed: 11/28/2022]
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10
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Ranjbar B, Gill P. Circular Dichroism Techniques: Biomolecular and Nanostructural Analyses- A Review. Chem Biol Drug Des 2009; 74:101-20. [DOI: 10.1111/j.1747-0285.2009.00847.x] [Citation(s) in RCA: 403] [Impact Index Per Article: 26.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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11
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Loss of structural integrity and hydrophobic ligand binding capacity of acetylated and succinylated bovine β-lactoglobulin. Int Dairy J 2009. [DOI: 10.1016/j.idairyj.2008.06.011] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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12
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Structural studies of hen egg-white lysozyme dimer: Comparison with monomer. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2008; 1784:1043-9. [DOI: 10.1016/j.bbapap.2008.03.010] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2007] [Revised: 03/02/2008] [Accepted: 03/14/2008] [Indexed: 11/18/2022]
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13
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Tafreshi NK, Sadeghizadeh M, Emamzadeh R, Ranjbar B, Naderi-Manesh H, Hosseinkhani S. Site-directed mutagenesis of firefly luciferase: implication of conserved residue(s) in bioluminescence emission spectra among firefly luciferases. Biochem J 2008; 412:27-33. [PMID: 18251715 DOI: 10.1042/bj20070733] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2023]
Abstract
The bioluminescence colours of firefly luciferases are determined by assay conditions and luciferase structure. Owing to red light having lower energy than green light and being less absorbed by biological tissues, red-emitting luciferases have been considered as useful reporters in imaging technology. A set of red-emitting mutants of Lampyris turkestanicus (Iranian firefly) luciferase has been made by site-directed mutagenesis. Among different beetle luciferases, those from Phrixothrix (railroad worm) emit either green or red bioluminescence colours naturally. By substitution of three specific amino acids using site-specific mutagenesis in a green-emitting luciferase (from L. turkestanicus), the colour of emitted light was changed to red concomitant with decreasing decay rate. Different specific mutations (H245N, S284T and H431Y) led to changes in the bioluminescence colour. Meanwhile, the luciferase reaction took place with relative retention of its basic kinetic properties such as K(m) and relative activity. Structural comparison of the native and mutant luciferases using intrinsic fluorescence, far-UV CD spectra and homology modelling revealed a significant conformational change in mutant forms. A change in the colour of emitted light indicates the critical role of these conserved residues in bioluminescence colour determination among firefly luciferases. Relatively high specific activity and emission of red light might make these mutants suitable as reporters for the study of gene expression and bioluminescence imaging.
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Affiliation(s)
- Narges Kh Tafreshi
- Department of Genetics, Faculty of Basic Sciences, Tarbiat Modares University, Tehran, Iran
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14
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Mortazavi M, Hosseinkhani S, Khajeh K, Ranjbar B, Emamzadeh AR. Spectroscopic and functional characterization of Lampyris turkestanicus luciferase: a comparative study. Acta Biochim Biophys Sin (Shanghai) 2008; 40:365-74. [PMID: 18465021 DOI: 10.1111/j.1745-7270.2008.00411.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Functional expression and spectroscopic analysis of luciferases from Lampyris turkestanicus and Photinus pyralis were carried out. cDNA encoding L. turkestanicus luciferase was isolated by reverse transcription-polymerase chain reaction, cloned, and functionally expressed in Escherichia coli. The luciferases were purified to homogeneity using Ni-nitrilotriacetic acid Sepharose, and kinetic properties of luciferase from L. turkestanicus were compared with that from P. pyralis. Amino acid differences in its primary structures in relation to P. pyralis luciferase brought about changes in the kinetic properties of the enzyme as evidenced by substantial lowering of Km for ATP, increased light decay time, and decreased thermostability. Luciferase from L. turkestanicus was used to carry out Michaelis-Menten kinetics with a Km of 95.5 muM for ATP and 20 muM for luciferin. Maximum activity was recorded at pH 8.5, so it might be a suitable reporter for microbial screening at alkaline pH. Tryptophan fluorescence for P. pyralis luciferase was higher than L. turkestanicus luciferase. Substitution of some residues in L. turkestanicus luciferase appears to change the kinetic properties by inducing a substantial tertiary structural change, without a large effect on secondary structural elements, as revealed by intrinsic and extrinsic fluorescence, Fourier transform infrared spectroscopy, and near-ultraviolet circular dichroism spectra.
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Affiliation(s)
- Mojtaba Mortazavi
- Department of Biochemistry, Faculty of Basic Sciences, Tarbiat Modares University, Tehran P. O. Box 14115-175, Iran.
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15
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Shirazy NH, Ranjbar B, Hosseinkhani S, Khalifeh K, Madvar AR, Naderi-Manesh H. Critical Role of Glu175 on Stability and Folding of Bacterial Luciferase: Stopped-flow Fluorescence Study. BMB Rep 2007; 40:453-8. [PMID: 17669259 DOI: 10.5483/bmbrep.2007.40.4.453] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacterial luciferase is a heterodimeric enzyme, which catalyzes the light emission reaction, utilizing reduced FMN (FMNH2), a long chain aliphatic aldehyde and O(2), to produce green-blue light. This enzyme can be readily classed as slow or fast decay based on their rate of luminescence decay in a single turnover. Mutation of Glu175 in alpha subunit to Gly converted slow decay Xenorhabdus Luminescence luciferase to fast decay one. The following studies revealed that changing the luciferase flexibility and lake of Glu-flavin interactions are responsible for the unusual kinetic properties of mutant enzyme. Optical and thermodynamics studies have caused a decrease in free energy and anisotropy of mutant enzyme. Moreover, the role of Glu175 in transition state of folding pathway by use of stopped-flow fluorescence technique has been studied which suggesting that Glu175 is not involved in transition state of folding and appears as surface residue of the nucleus or as a member of one of a few alternative folding nuclei. These results suggest that mutation of Glu175 to Gly extended the structure of Xenorhabdus Luminescence luciferase, locally.
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Affiliation(s)
- Najmeh Hadizadeh Shirazy
- Department of Biophysics and Biochemistry, Tarbiat Modares University, P.O. Box: 14115-175, Tehran, Iran
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16
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Mossavarali S, Hosseinkhani S, Ranjbar B, Miroliaei M. Stepwise modification of lysine residues of glucose oxidase with citraconic anhydride. Int J Biol Macromol 2006; 39:192-6. [PMID: 16682074 DOI: 10.1016/j.ijbiomac.2006.03.018] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2006] [Revised: 03/18/2006] [Accepted: 03/18/2006] [Indexed: 12/01/2022]
Abstract
Structural properties of modified forms of glucose oxidase made by stepwise specific modification have been investigated. By a single step modification, one of the modified forms resulted in the conversion of native structure of glucose oxidase to molten globule like form [S. Hosseinkhani, B. Ranjbar, H. Naderi-Manesh, M. Nemat-Gorgani, FEBS Lett. 561 (2004) 213-216]. Chemical modification of lysine residues in glucose oxidase was carried out using different concentration of citraconic anhydride. Modification brought about changes in the tertiary structure with some degree of alteration in secondary structure. FTIR, far and near-UV CD spectropolarimetry, intrinsic and extrinsic fluorescence spectroscopy showed structural changes of glucose oxidase in a concentration dependent manner. This was supported by comparative study of secondary and tertiary structure.
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Affiliation(s)
- Shahla Mossavarali
- Department of Biochemistry, Faculty of Basic Sciences, Tarbiat Modarres University, Tehran, Iran
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17
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Hassani L, Ranjbar B, Khajeh K, Naderi-Manesh H, Naderi-Manesh M, Sadeghi M. Horseradish peroxidase thermostabilization: The combinatorial effects of the surface modification and the polyols. Enzyme Microb Technol 2006. [DOI: 10.1016/j.enzmictec.2005.05.006] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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18
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Madvar AR, Hosseinkhani S, Khajeh K, Ranjbar B, Asoodeh A. Implication of a critical residue (Glu175) in structure and function of bacterial luciferase. FEBS Lett 2005; 579:4701-6. [PMID: 16098518 DOI: 10.1016/j.febslet.2005.07.040] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2005] [Revised: 06/22/2005] [Accepted: 07/01/2005] [Indexed: 11/30/2022]
Abstract
Structural properties of a bacterial luciferase mutant, evolved by random mutagenesis, have been investigated. Bacterial luciferases (LuxAB) can be readily classed as slow or fast decay luciferases based on their rates of luminescence decay in a single turnover assay. By random mutagenesis, one of the mutants generated by a single mutation on LuxA at position 175 (E175G) resulted in the "slow decay" Xenorhabdus luminescens luciferase was converted into a luciferase with a significantly more rapid decay rate [Hosseinkhani, S., Szittner, R. and Meighen, E.A. (2005) Biochemical Journal 385, 575-580]. A single mutation (E175G), in a loop that connects alpha helix 5 and beta sheet 5 brought about changes in the kinetic and structural properties of the enzyme. Enhancement of tryptophan fluorescence was observed with a lower degree of fluorescence quenching by acrylamide upon mutation. Near- and far-UV circular dichroism spectra of the native and mutant forms suggested formation of an intermediate structure, further supported by 8-anilino-1-naphthalene-sulphonic acid (ANS) fluorescence which indicated lower exposure of hydrophobic residues as a result of mutation. Fluorescence quenching studies utilizing acrylamide indicated a more accessible fluor for the native form. Thus, the E175G point mutation appears to change the enzymatic decay rate by inducing a substantial tertiary structural change, without a large effect on secondary structural elements, as revealed by Fourier transform IR spectroscopy. Overall, the mutation caused structural changes that go beyond the simple change in orientation of Glu175.
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Affiliation(s)
- Ali Riahi Madvar
- Department of Biochemistry, Faculty of Basic Sciences, Tarbiat Modarres University, Tehran, Iran
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