1
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Chaubey MG, Patel SN, Rastogi RP, Srivastava PL, Singh AK, Madamwar D, Singh NK. Therapeutic potential of cyanobacterial pigment protein phycoerythrin: in silico and in vitro study of BACE1 interaction and in vivo Aβ reduction. Int J Biol Macromol 2019; 134:368-378. [PMID: 31059742 DOI: 10.1016/j.ijbiomac.2019.05.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2018] [Revised: 03/29/2019] [Accepted: 05/02/2019] [Indexed: 12/18/2022]
Abstract
Cyanobacteria are an immense source of innovative classes of pharmacologically active compounds exhibiting various biological activities ranging from antioxidants, antibiotics, anticancer, anti-inflammatory to anti-Alzheimer's disease. In the present study, we primarily targeted the inhibition of Beta-site amyloid precursor protein cleaving enzyme-1 (BACE1) by a naturally occurring cyanobacterial protein phycoerythrin (C-PE). BACE1 cleaves amyloid-β precursor protein (APP) and leads to accumulation of neurotoxic amyloid beta (Aβ) plaques in the brain, as an attribute of Alzheimer's disease (AD). Inhibition of BACE1 was measured in terms of their association and dissociation rate constants, thermodynamics of binding using surface plasmon resonance (SPR) and isothermal titration calorimetry (ITC). The kinetic parameters for enzyme activity were also measured using synthetic decapeptide as a substrate. We further validated the potential of PE by in-vivo histopathological staining of Aβ aggregate mutant Caenorhabditis elegans CL4176 by Thioflavin-T. The present studies pave the way for the application of naturally occurring C-PE as a putative therapeutic drug for the AD.
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Affiliation(s)
- Mukesh Ghanshyam Chaubey
- Department of Biotechnology, Shree A. N. Patel PG Institute of Science and Research, Sardar Patel University, Anand 388001, Gujarat, India
| | - Stuti Nareshkumar Patel
- Post-Graduate Department of Biosciences, UGC-Centre of Advanced Study, Satellite Campus, Vadtal Road, Sardar Patel University, Bakrol, 388315 Anand, Gujarat, India
| | - Rajesh Prasad Rastogi
- Post-Graduate Department of Biosciences, UGC-Centre of Advanced Study, Satellite Campus, Vadtal Road, Sardar Patel University, Bakrol, 388315 Anand, Gujarat, India
| | - Prabhakar Lal Srivastava
- Symbiosis School of Biological Science, Symbiosis International (Deemed University), Lavale, 412115 Pune, Maharashtra, India
| | - Arun Kumar Singh
- Zydus Research Centre, Sarkhej-Bavla N.H. No. 8A, Moraiya, Sanand, Ahmedabad 382210, India
| | - Datta Madamwar
- Post-Graduate Department of Biosciences, UGC-Centre of Advanced Study, Satellite Campus, Vadtal Road, Sardar Patel University, Bakrol, 388315 Anand, Gujarat, India
| | - Niraj Kumar Singh
- Department of Biotechnology, Shree A. N. Patel PG Institute of Science and Research, Sardar Patel University, Anand 388001, Gujarat, India.
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2
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Escuder-Vieco D, Espinosa-Martos I, Rodríguez JM, Fernández L, Pallás-Alonso CR. Effect of HTST and Holder Pasteurization on the Concentration of Immunoglobulins, Growth Factors, and Hormones in Donor Human Milk. Front Immunol 2018; 9:2222. [PMID: 30319659 PMCID: PMC6170621 DOI: 10.3389/fimmu.2018.02222] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Accepted: 09/07/2018] [Indexed: 02/06/2023] Open
Abstract
Donor human milk (DHM) is submitted to Holder pasteurization (HoP) to ensure its microbiological safety in human milk banks but this treatment affects some of its bioactive compounds. The objective of this work was to compare the effects of HoP and high temperature short time (HTST) treatments on some bioactive compounds found in DHM. A total of 24 DHM batches were processed in a continuous HTST system (70, 72, and 75°C for 5-25 s) and by HoP (62.5°C for 30 min). The concentrations of immunoglobulins (Igs) A, G, and M, transforming growth factor-beta 2 (TGF-β2), adiponectine, ghrelin, and leptin were measured using a multiplex system, whereas the concentration of epidermal growth factor (EGF) was determined by ELISA. In relation to Igs, IgG showed the highest preservation rates (87-101%) after HTST treatments, followed by IgA (54-88%) and IgM (25-73%). Ig retention after any of the HTST treatments was higher than after HoP (p < 0.001). Treatment times required to reduce the concentration of IgM by 90% (D-value) were 130, 88, and 49 s at 70, 72, and 75°C, while the number of degrees Celsius required to change the D-value by one factor of 10 (z-value) was 11.79°C. None of the heat treatments had a significant effect on the concentrations of TGF-β2, EGF, adiponectin, and ghrelin. In contrast, leptin was detected only in 4 of the samples submitted to HoP, whereas it was present in all samples after the different HTST treatments, with retention rates ranging between 34 and 68%. Globally, the concentration of IgA, IgG, IgM, and leptin in DHM was significantly higher after HTST pasteurization performed in a continuous system designed to be used in human milk banks than after the HoP procedure that is routinely applied at present.
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Affiliation(s)
- Diana Escuder-Vieco
- Banco Regional de Leche Materna, Hospital Universitario 12 de Octubre, Instituto de Investigación i+12, Madrid, Spain
- *Correspondence: Diana Escuder-Vieco
| | | | - Juan M. Rodríguez
- Sección Departamental de Nutrición y Ciencia de los Alimentos (Veterinaria), Universidad Complutense de Madrid, Madrid, Spain
| | - Leónides Fernández
- Sección Departamental de Farmacia Galénica y Tecnología Alimentaria (Veterinaria), Universidad Complutense de Madrid, Madrid, Spain
| | - Carmen Rosa Pallás-Alonso
- Banco Regional de Leche Materna, Hospital Universitario 12 de Octubre, Instituto de Investigación i+12, Madrid, Spain
- Servicio de Neonatología, Hospital Universitario 12 de Octubre, Instituto de Investigación i+12, Universidad Complutense de Madrid, Madrid, Spain
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3
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Kozer N, Rothacker J, Burgess AW, Nice EC, Clayton AHA. Conformational Dynamics in a Truncated Epidermal Growth Factor Receptor Ectodomain. Biochemistry 2011; 50:5130-9. [DOI: 10.1021/bi200095w] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Noga Kozer
- Centre for Micro-photonics, Faculty of Engineering and Industrial Sciences, Swinburne University of Technology, Victoria 3122, Australia
| | - Julie Rothacker
- The Ludwig Institute for Cancer Research, Melbourne-Parkville Branch, P.O. Box 2008, Royal Melbourne Hospital, Victoria 3050, Australia
| | - Antony W. Burgess
- The Ludwig Institute for Cancer Research, Melbourne-Parkville Branch, P.O. Box 2008, Royal Melbourne Hospital, Victoria 3050, Australia
| | - Edouard C. Nice
- The Ludwig Institute for Cancer Research, Melbourne-Parkville Branch, P.O. Box 2008, Royal Melbourne Hospital, Victoria 3050, Australia
- Department of Biochemistry, Monash University, Clayton, Victoria 3080, Australia
| | - Andrew H. A. Clayton
- Centre for Micro-photonics, Faculty of Engineering and Industrial Sciences, Swinburne University of Technology, Victoria 3122, Australia
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Kalkhof S, Witte K, Ihling CH, Müller MQ, Keller MV, Haehn S, Smyth N, Paulsson M, Sinz A. A Novel Disulfide Pattern in Laminin-Type Epidermal Growth Factor-like (LE) Modules of Laminin β1 and γ1 Chains. Biochemistry 2010; 49:8359-66. [DOI: 10.1021/bi101187f] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Stefan Kalkhof
- Department of Pharmaceutical Chemistry and Bioanalytics, Institute of Pharmacy, Martin Luther University Halle-Wittenberg, D-06120 Halle (Saale), Germany
| | - Konstanze Witte
- Department of Pharmaceutical Chemistry and Bioanalytics, Institute of Pharmacy, Martin Luther University Halle-Wittenberg, D-06120 Halle (Saale), Germany
| | - Christian H. Ihling
- Department of Pharmaceutical Chemistry and Bioanalytics, Institute of Pharmacy, Martin Luther University Halle-Wittenberg, D-06120 Halle (Saale), Germany
| | - Mathias Q. Müller
- Department of Pharmaceutical Chemistry and Bioanalytics, Institute of Pharmacy, Martin Luther University Halle-Wittenberg, D-06120 Halle (Saale), Germany
| | - Manuel V. Keller
- Center for Biochemistry and Center for Molecular Medicine, Faculty of Medicine, University of Cologne, D-50931 Cologne, Germany
- Cologne Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD), D-50931 Cologne, Germany
| | - Sebastian Haehn
- Center for Biochemistry and Center for Molecular Medicine, Faculty of Medicine, University of Cologne, D-50931 Cologne, Germany
| | - Neil Smyth
- School of Biological Sciences, University of Southampton, East Southampton SO16 7PX, United Kingdom
| | - Mats Paulsson
- Center for Biochemistry and Center for Molecular Medicine, Faculty of Medicine, University of Cologne, D-50931 Cologne, Germany
- Cologne Excellence Cluster on Cellular Stress Responses in Aging Associated Diseases (CECAD), D-50931 Cologne, Germany
| | - Andrea Sinz
- Department of Pharmaceutical Chemistry and Bioanalytics, Institute of Pharmacy, Martin Luther University Halle-Wittenberg, D-06120 Halle (Saale), Germany
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Yan C, Pattani V, Tunnell JW, Ren P. Temperature-induced unfolding of epidermal growth factor (EGF): insight from molecular dynamics simulation. J Mol Graph Model 2010; 29:2-12. [PMID: 20466569 DOI: 10.1016/j.jmgm.2010.03.011] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2010] [Revised: 03/15/2010] [Accepted: 03/29/2010] [Indexed: 10/19/2022]
Abstract
Thermal disruption of protein structure and function is a potentially powerful therapeutic vehicle. With the emerging nanoparticle-targeting and femtosecond laser technology, it is possible to deliver heating locally to specific molecules. It is therefore important to understand how fast a protein can unfold or lose its function at high temperatures, such as near the water boiling point. In this study, the thermal damage of EGF was investigated by combining the replica exchange (136 replicas) and conventional molecular dynamics simulations. The REMD simulation was employed to rigorously explore the free-energy landscape of EGF unfolding. Interestingly, besides the native and unfolded states, we also observed a distinct molten globule (MG) state that retained substantial amount of native contacts. Based on the understanding that which the unfolding of EGF is a three-state process, we have examined the unfolding kinetics of EGF (N-->MG and MG-->D) with multiple 20-ns conventional MD simulations. The Arrhenius prefactors and activation energy barriers determined from the simulation are within the range of previously studied proteins. In contrast to the thermal damage of cells and tissues which take place on the time scale of seconds to hours at relatively low temperatures, the denaturation of proteins occur in nanoseconds when the temperature of heat bath approaches the boiling point.
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Affiliation(s)
- Chunli Yan
- Department of Biomedical Engineering, University of Texas, Austin, TX 78712, USA
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6
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Chang JY. Structural heterogeneity of 6 M GdmCl-denatured proteins: implications for the mechanism of protein folding. Biochemistry 2009; 48:9340-6. [PMID: 19728745 DOI: 10.1021/bi901417f] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
An in vitro experiment with protein folding is typically initiated with 6 M GdmCl-denatured proteins, which are generally considered fully unfolded. However, studies conducted by various laboratories have shown that many 6 M GdmCl-denatured proteins are structurally heterogeneous and still retain nativelike residual structures. The extent of conformational heterogeneity of the 6 M GdmCl-denatured protein has significant implications for the folding landscape as well as the interpretation of the observed early stage folding mechanism. Using the method of disulfide scrambling, we are able to gain rough insight into the diverse structural properties of 6 M GdmCl-denatured proteins. It demonstrates that most 6 M GdmCl-denatured proteins are approximately fully denatured, but partially unfolded. Most of them comprise diverse conformational isomers. We review here the cumulative evidence obtained from various laboratories and also provide experimental data obtained in our laboratory.
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Affiliation(s)
- Jui-Yoa Chang
- Department of Biochemistry and Molecular Biology, Research Center for Protein Chemistry, Brown Foundation Institute of Molecular Medicine, University of Texas, Houston, Texas 77030, USA.
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7
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Goelz R, Hihn E, Hamprecht K, Dietz K, Jahn G, Poets C, Elmlinger M. Effects of different CMV-heat-inactivation-methods on growth factors in human breast milk. Pediatr Res 2009; 65:458-61. [PMID: 19127217 DOI: 10.1203/pdr.0b013e3181991f18] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Preterm infants can inoculate virulent cytomegalovirus (CMV) through their mothers' raw breast milk. Complete virus inactivation is achieved only by heat treatment, but the effect on growth factors has never been assessed systematically. Insulin-like-growth-factor-1-, IGF-2-, insulin-like-growth-factor-binding-protein-2-, and IGFBP-3-concentrations were measured, before and after heating, in 51 breast-milk-samples from 28 mothers, and epidermal-growth-factor-concentrations in a subgroup of 35 samples from 22 mothers. Two heating methods were applied: Short-term (5 s) pasteurisation at 62, 65, and 72 degrees C, and long-term Holder-Pasteurisation (30 min) at 63 degrees C. IGF-1, IGF-2, IGFBP-2, and IGFBP-3 were measured by RIA, and EGF by ELISA. Heating for 30 min decreased significantly IGF-1 by 39.4%, IGF-2 by 9.9%, IGFBP-2 by 19.1%, and IGFBP-3 by 7.0%. In contrast, IGF-1, IGF-2, IGFBP-2, and IGFBP-3 were not altered significantly when using a short heating duration of 5 s, irrespective of the level of temperature, except for IGF-2 at 62 degrees C for 5 s (p = 0.041) and IGFBP-2 at 72 degrees C for 5 s (p = 0.025). Neither long- nor short-time heating methods changed the concentration of EGF. Only short heating methods (5 s, 62-72 degrees C) can preserve, almost completely, the concentrations of IGFs in human milk, whereas Holder-Pasteurization does not.
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Affiliation(s)
- Rangmar Goelz
- Department of Neonatology, University Hospital, Tuebingen, Germany.
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8
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Abstract
Five highly homologous epidermal growth factor receptor ligands were studied by mass spectral analysis, hydrogen/deuterium (H/D) exchange via attenuated total reflectance Fourier transform-infrared spectroscopy, and two-dimensional correlation analysis. These studies were performed to determine the order of events during the exchange process, the extent of H/D exchange, and associated kinetics of exchange for a comparative analysis of these ligands. Furthermore, the secondary structure composition of amphiregulin (AR) and heparin-binding-epidermal growth factor (HB-EGF) was determined. All ligands were found to have similar contributions of 3(10)-helix and random coil with varying contributions of beta-sheets and beta-turns. The extent of exchange was 40%, 65%, 55%, 65%, and 98% for EGF, transforming growth factor-alpha (TGF-alpha), AR, HB-EGF, and epiregulin (ER), respectively. The rate constants were determined and classified as fast, intermediate, and slow: for EGF the 0.20 min(-1) (Tyr), 0.09 min(-1) (Arg, beta-turns), and 1.88 x 10(-3) min(-1) (beta-sheets and 3(10)-helix); and for TGF-alpha 0.91 min(-1) (Tyr), 0.27 min(-1) (Arg, beta-turns), and 1.41 x 10(-4) min(-1) (beta-sheets). The time constants for AR 0.47 min(-1) (Tyr), 0.04 min(-1) (Arg), and 1.00 x 10(-4) min(-1) (buried 3(10)-helix, beta-turns, and beta-sheets); for HB-EGF 0.89 min(-1) (Tyr), 0.14 min(-1) (Arg and 3(10)-helix), and 1.00 x 10(-3) min(-1) (buried 3(10)-helix, beta-sheets, and beta-turns); and for epiregulin 0.16 min(-1) (Tyr), 0.03 min(-1) (Arg), and 1.00 x 10(-4) min(-1) (3(10)-helix and beta-sheets). These results provide essential information toward understanding secondary structure, H/D exchange kinetics, and solvation of these epidermal growth factor receptor ligands in their unbound state.
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9
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Latif MMAE, . EMD, . LMAEL, . NAEL. Urinary Epidermal Growth Factor Excretion: A Useful Prognostic Marker for Progression of Renal Damage in Children. JOURNAL OF MEDICAL SCIENCES 2007. [DOI: 10.3923/jms.2007.1171.1176] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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10
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Lin CCJ, Lu BY, Chang JY. Conformational stability of secretory leucocyte protease inhibitor: A protein with no hydrophobic core and very little secondary structure. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2006; 1764:1286-91. [PMID: 16807147 DOI: 10.1016/j.bbapap.2006.05.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2006] [Revised: 05/16/2006] [Accepted: 05/17/2006] [Indexed: 11/16/2022]
Abstract
Conformational stability of proteins (including disulfide containing proteins) has been routinely characterized by spectroscopic techniques. Proteins which lack adequate signal of circular dichroism may require unconventional technique. Secretory Leucocyte Protease Inhibitor (SLPI) is a 107 amino acids protein with a high density of disulfide pairing (eight). The native SLPI has no hydrophobic core and contains very little hydrogen bonded secondary structure [Gruetter, M., Fendrich, G., Huber, R., and Bode, W. (1988) The 2.5 A X-ray crystal structure of the acid stable proteinase inhibitor from human mucous secretions analyzed in its complex with bovine alpha-chymotrypsin. The EMBO J. 7, 345-352.]. In this study, conformational stability of SLPI has been investigated by the method of disulfide scrambling, which permits quantification of the native and denatured (scrambled) proteins by HPLC. Due to high heterogeneity of denatured SLPI, the native and scrambled SLPI are extensively overlapped on HPLC. This impediment was further overcome by the development of a novel method which distinguishes the native and scrambled isomers of SLPI by exploiting the relative stability of their disulfide bonds. The study reveals mid-point denaturation of SLPI at 1.36 M of GdmSCN, 4.0 M of GdmCl and >8 M urea. Based on the GdmCl denaturation curve, the unfolding free energy (DeltaG(H20)) of SLPI was estimated to be 4.56 kcal/mol. The results of our studies suggest an alternative strategy for analyzing conformational stability of disulfide proteins that are not suitable to the conventional spectroscopic techniques.
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Affiliation(s)
- Curtis C-J Lin
- Research Center for Protein Chemistry, Institute of Molecular Medicine and the Department of Biochemistry and Molecular Biology, The University of Texas, 2121 W. Holcombe Blvd., Houston, TX 77030, USA
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11
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Chang JY, Lu BY, Li L. Conformational impurity of disulfide proteins: Detection, quantification, and properties. Anal Biochem 2005; 342:78-85. [PMID: 15958183 DOI: 10.1016/j.ab.2005.03.038] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2005] [Revised: 03/13/2005] [Accepted: 03/22/2005] [Indexed: 11/24/2022]
Abstract
The conformations of native proteins are in principle, and in most cases, dictated by the law of thermodynamics. Accordingly, a native protein must always exist in equilibrium with a minor concentration of nonnative (denatured) conformational isomers even at nondenaturing conditions. The presence of an infinitesimal quantity of nonnative conformational isomers at physiological conditions is biologically relevant due to their propensity to aggregate, which is an underlying cause of many neurodegenerative diseases. However, their detection and quantification are inherently difficult. In this article, we describe a simple strategy using the technique of disulfide scrambling to identify and quantify such minute concentrations of nonnative isomers. It is demonstrated that even for small stable proteins such as epidermal growth factor and hirudin, approximately 1% of heterogeneous nonnative isomers coexist with the native proteins under physiological conditions.
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Affiliation(s)
- Jui-Yoa Chang
- Center for Protein Chemistry, Brown Foundation Institute of Molecular Medicine for the Prevention of Human Diseases, University of Texas, Houston, TX 77030, USA.
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12
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Zanuttin F, Guarnaccia C, Pintar A, Pongor S. Folding of epidermal growth factor-like repeats from human tenascin studied through a sequence frame-shift approach. ACTA ACUST UNITED AC 2004; 271:4229-40. [PMID: 15511229 DOI: 10.1111/j.1432-1033.2004.04363.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
In order to investigate the factors that determine the correct folding of epidermal growth factor-like (EGF) repeats within a multidomain protein, we prepared a series of six peptides that, taken together, span the sequence of two EGF repeats of human tenascin, a large protein from the extracellular matrix. The peptides were selected by sliding a window of the average length of tenascin EGF repeats over the sequence of EGF repeats 13 and 14. We thus obtained six peptides, EGF-f1 to EGF-f6, that are 33 residues long, contain six cysteines each, and bear a partial overlap in the sequence. While EGF-f1 corresponds to the native EGF-14 repeat, the others are frame-shifted EGF repeats. We carried out the oxidative folding of these peptides in vitro, analyzed the reaction mixtures by acid trapping followed by LC-MS, and isolated some of the resulting products. The oxidative folding of the native EGF-14 peptide is fast, produces a single three-disulfide species with an EGF-like disulfide topology and a marked difference in the RP-HPLC retention time compared with the starting product. On the contrary, frame-shifted peptides fold more slowly and give mixtures of three-disulfide species displaying RP-HPLC retention times that are closer to those of the reduced peptides. In contrast to the native EGF-14, the three-disulfide products that could be isolated are mainly unstructured, as determined by CD and NMR spectroscopy. We conclude that both kinetics and thermodynamics drive the correct pairing of cysteines, and speculate about how cysteine mispairing could trigger disulfide reshuffling in vivo.
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Affiliation(s)
- Francesco Zanuttin
- International Centre for Genetic Engineering and Biotechnology, Protein Structure and Bioinformatics Group, Trieste, Italy
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13
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Cemazar M, Zahariev S, Pongor S, Hore PJ. Oxidative Folding of Amaranthus α-Amylase Inhibitor. J Biol Chem 2004; 279:16697-705. [PMID: 14749333 DOI: 10.1074/jbc.m312328200] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Oxidative folding is the fusion of native disulfide bond formation with conformational folding. This complex process is guided by two types of interactions: first, covalent interactions between cysteine residues, which transform into native disulfide bridges, and second, non-covalent interactions giving rise to secondary and tertiary protein structure. The aim of this work is to understand both types of interactions in the oxidative folding of Amaranthus alpha-amylase inhibitor (AAI) by providing information both at the level of individual disulfide species and at the level of amino acid residue conformation. The cystine-knot disulfides of AAI protein are stabilized in an interdependent manner, and the oxidative folding is characterized by a high heterogeneity of one-, two-, and three-disulfide intermediates. The formation of the most abundant species, the main folding intermediate, is favored over other species even in the absence of non-covalent sequential preferences. Time-resolved NMR and photochemically induced dynamic nuclear polarization spectroscopies were used to follow the oxidative folding at the level of amino acid residue conformation. Because this is the first time that a complete oxidative folding process has been monitored with these two techniques, their results were compared with those obtained at the level of an individual disulfide species. The techniques proved to be valuable for the study of conformational developments and aromatic accessibility changes along oxidative folding pathways. A detailed picture of the oxidative folding of AAI provides a model study that combines different biochemical and biophysical techniques for a fuller understanding of a complex process.
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Affiliation(s)
- Masa Cemazar
- International Centre for Genetic Engineering and Biotechnology, Padriciano 99, 34012 Trieste, Italy.
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14
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Singh RR, Chang JY. Investigating conformational stability of bovine pancreatic phospholipase A2: a novel concept in evaluating the contribution of the 'native-framework' of disulphides to the global conformational stability of proteins. Biochem J 2004; 377:685-92. [PMID: 14533980 PMCID: PMC1223891 DOI: 10.1042/bj20030968] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2003] [Revised: 09/23/2003] [Accepted: 10/08/2003] [Indexed: 11/17/2022]
Abstract
Bovine pancreatic PLA(2) (phospholipase A(2)) is a 14 kDa protein whose structure is highly cross-linked by seven disulphide bonds. We investigated the structural stability of this enzyme by the method of 'disulphide-scrambling' with denaturants such as urea, GdmCl (guanidine hydrochloride), GdmSCN (guanidine thiocyanate) and at high temperatures in the presence of 2-mercaptoethanol (0.2 mM) as thiol initiator. Reverse-phase HPLC was used to follow denaturation. To denature 50% of the native protein, 1.25 M GdmSCN, approx. 3 M GdmCl and higher than 8 M urea were required. Only 20% of the protein was denatured after 2 h at 60 degrees C, whereas complete denaturation was seen after 2 h at 70 degrees C and within 30 min at 80 degrees C. A distinct enhancement of stability was observed when denaturation was conducted in the presence of 10 mM calcium chloride, which has not been reported previously. CD studies of GdmCl denaturation of bovine PLA(2) showed that 2.5 M GdmCl was required to denature 50% of the protein in the presence of 0.2 mM 2-mercaptoethanol (in agreement with the HPLC analysis), whereas 6.4 M GdmCl was necessary to denature 50% of the protein in the absence of a thiol initiator. Conformational stability (Delta G (water)) was estimated to be 8.7 kcal/mol (1 cal=4.184 J) by 'disulphide-intact' denaturation (where 'native' disulphide framework was unaffected) and 2.5 kcal/mol by 'disulphide-scrambling' denaturation (involved breaking of native disulphides and formation of 'non-native' ones). The difference, Delta(Delta G (water)), of 6.2 kcal/mol was the conformational stability contributed by the 'native-framework' of seven disulphides. Using bovine PLA(2) as an example, we have demonstrated a novel comparative technique, where the conformational stability study of a disulphide-containing protein, with a common denaturant, in both the presence and absence of catalytic amounts of a thiol initiator can be used as a convenient method to estimate selectively and quantitatively the actual contribution of the 'native disulphide bond network' towards the global conformational stability of the protein.
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Affiliation(s)
- R Rajesh Singh
- Research Center for Protein Chemistry, Institute of Molecular Medicine and the Department of Biochemistry and Molecular Biology, The University of Texas, Houston, TX 77030, U.S.A
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