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Functional EGF domain of the human neuregulin 1α produced in Escherichia coli with accurate disulfide bonds. Mol Biol Rep 2022; 49:11715-11727. [PMID: 36198848 DOI: 10.1007/s11033-022-07956-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Accepted: 09/17/2022] [Indexed: 10/10/2022]
Abstract
BACKGROUND Neuregulins comprise a large family of growth factors containing an epidermal growth factor (EGF) domain. NRG1 acts in signaling pathways involved in proliferation, apoptosis, migration, differentiation, and adhesion of many normal cell types and in human diseases. The EGF domain of NRG1 mediates signaling by interaction with members of the ErbB family of receptors. Easy access to correctly folded hNRG1α EGF domain can be a valuable tool to investigate its function in different cell types. MATERIALS AND METHODS The EGF domain of hNRG1α was produced in Escherichia coli in fusion with TrxA and purified after cleavage of TrxA. Conformation and stability analyses were performed by using biophysical methods and the disulfide bonds were mapped by mass spectrometry. The activity of the hNRG1α EGF domain was demonstrated in cell proliferation and migration assays. RESULTS Approximately 3.3 mg of hNRG1α EGF domain were obtained starting from a 0.5 L of E. coli culture. Correct formation of the three disulfide bonds was demonstrated by mass spectrometry with high accuracy. Heat denaturation assays monitored by circular dichroism and dynamic light scattering revealed that it is a highly stable protein. The recombinant EGF domain of hNRG1α purified in this work is highly active, inducing cell proliferation at concentration as low as 0.05 ng/mL. It induces also cell migration as demonstrated by a gap closure assay. CONCLUSION The EGF domain of hNRG1α was produced in E. coli with the correct disulfide bonds and presented high stimulation of HeLa cell proliferation and NDFH cell migration.
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Protein-induced metamorphosis of unilamellar lipid vesicles to multilamellar hybrid vesicles. J Control Release 2021; 331:187-197. [PMID: 33422501 DOI: 10.1016/j.jconrel.2021.01.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Revised: 12/19/2020] [Accepted: 01/05/2021] [Indexed: 12/17/2022]
Abstract
Protein encapsulation into nanocarriers has been extensively studied to improve the efficacy and stability of therapeutic proteins. However, the chemical modification of proteins or new synthetic carrier materials are essential to achieve a high encapsulation efficiency and structural stability of proteins, which hinders their clinical applications. New strategies to physically incorporate proteins into nanocarriers feasible for clinical uses are required to overcome the current limitation. Here we report the spontaneous protein-induced reorganization of 'pre-formed' unilamellar lipid vesicles to efficiently incorporate proteins within multilamellar protein-lipid hybrid vesicles without chemical modification. Epidermal growth factor (EGF) binds to the surface of cationic unilamellar lipid vesicles and induces layer-by-layer self-assembly of the vesicles. The protein is spontaneously entrapped in the interstitial layers of a multilamellar structure with extremely high loading efficiency, ~99%, through polyionic interactions as predicted by molecular dynamics simulation. The loaded protein exhibits much higher structural, chemical, and biological stability compared to free protein. The method is also successfully applied to several other proteins. This work provides a promising method for the highly efficient encapsulation of therapeutic proteins into multilamellar lipid vesicles without the use of specialized instruments, high energy, coupling agents, or organic solvents.
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Santonocito R, Venturella F, Dal Piaz F, Morando MA, Provenzano A, Rao E, Costa MA, Bulone D, San Biagio PL, Giacomazza D, Sicorello A, Alfano C, Passantino R, Pastore A. Recombinant mussel protein Pvfp-5β: A potential tissue bioadhesive. J Biol Chem 2019; 294:12826-12835. [PMID: 31292195 PMCID: PMC6709630 DOI: 10.1074/jbc.ra119.009531] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Revised: 06/28/2019] [Indexed: 12/23/2022] Open
Abstract
During their lifecycle, many marine organisms rely on natural adhesives to attach to wet surfaces for movement and self-defense in aqueous tidal environments. Adhesive proteins from mussels are biocompatible and elicit only minimal immune responses in humans. Therefore these proteins have received increased attention for their potential applications in medicine, biomaterials, and biotechnology. The Asian green mussel Perna viridis secretes several byssal plaque proteins, molecules that help anchoring the mussel to surfaces. Among these proteins, protein-5β (Pvfp-5β) initiates interactions with the substrate, displacing interfacial water molecules before binding to the surface. Here, we established the first recombinant expression in Escherichia coli of Pvfp-5β. We characterized recombinant Pvfp-5β, finding that despite displaying a CD spectrum consistent with features of a random coil, the protein is correctly folded as indicated by MS and NMR analyses. Pvfp-5β folds as a β-sheet-rich protein as expected for an epidermal growth factor-like module. We examined the effects of Pvfp-5β on cell viability and adhesion capacity in NIH-3T3 and HeLa cell lines, revealing that Pvfp-5β has no cytotoxic effects at the protein concentrations used and provides good cell-adhesion strength on both glass and plastic plates. Our findings suggest that the adhesive properties of recombinant Pvfp-5β make it an efficient surface-coating material, potentially suitable for biomedical applications including regeneration of damaged tissues.
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Affiliation(s)
- Radha Santonocito
- Istituto di Biofisica, Consiglio Nazionale delle Ricerche, Palermo I90146, Italy
| | - Francesca Venturella
- University of Palermo, Palermo I90128, Italy.,Fondazione Ri.MED, Palermo I90133, Italy
| | | | | | - Alessia Provenzano
- Istituto di Biofisica, Consiglio Nazionale delle Ricerche, Palermo I90146, Italy
| | - Estella Rao
- Istituto di Biofisica, Consiglio Nazionale delle Ricerche, Palermo I90146, Italy
| | - Maria Assunta Costa
- Istituto di Biofisica, Consiglio Nazionale delle Ricerche, Palermo I90146, Italy
| | - Donatella Bulone
- Istituto di Biofisica, Consiglio Nazionale delle Ricerche, Palermo I90146, Italy
| | | | - Daniela Giacomazza
- Istituto di Biofisica, Consiglio Nazionale delle Ricerche, Palermo I90146, Italy
| | - Alessandro Sicorello
- King's College London, London SE59RT, United Kingdom.,UK Dementia Research Institute at King's College London, London SE59RT, United Kingdom
| | | | - Rosa Passantino
- Istituto di Biofisica, Consiglio Nazionale delle Ricerche, Palermo I90146, Italy
| | - Annalisa Pastore
- King's College London, London SE59RT, United Kingdom.,UK Dementia Research Institute at King's College London, London SE59RT, United Kingdom
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Wang H, Agarwal P, Xiao Y, Peng H, Zhao S, Liu X, Zhou S, Li J, Liu Z, He X. A Nano-In-Micro System for Enhanced Stem Cell Therapy of Ischemic Diseases. ACS CENTRAL SCIENCE 2017; 3:875-885. [PMID: 28852702 PMCID: PMC5571461 DOI: 10.1021/acscentsci.7b00213] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Indexed: 05/12/2023]
Abstract
Stem cell therapy holds great potential for treating ischemic diseases. However, contemporary methods for local stem cell delivery suffer from poor cell survival/retention after injection. We developed a unique multiscale delivery system by encapsulating therapeutic agent-laden nanoparticles in alginate hydrogel microcapsules and further coentrapping the nano-in-micro capsules with stem cells in collagen hydrogel. The multiscale system exhibits significantly higher mechanical strength and stability than pure collagen hydrogel. Moreover, unlike nanoparticles, the nano-in-micro capsules do not move with surrounding body fluid and are not taken up by the cells. This allows a sustained and localized release of extracellular epidermal growth factor (EGF), a substance that could significantly enhance the proliferation of mesenchymal stem cells while maintaining their multilineage differentiation potential via binding with its receptors on the stem cell surface. As a result, the multiscale system significantly improves the stem cell survival at 8 days after implantation to ∼70% from ∼4-7% for the conventional system with nanoparticle-encapsulated EGF or free EGF in collagen hydrogel. After injecting into the ischemic limbs of mice, stem cells in the multiscale system facilitate tissue regeneration to effectively restore ∼100% blood perfusion in 4 weeks without evident side effects.
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Affiliation(s)
- Hai Wang
- Department of Biomedical Engineering, Comprehensive Cancer Center, Davis Heart and Lung
Research Institute, and Division of Cardiovascular Medicine,
and Department of Veterinary
Biosciences, The Ohio State University, Columbus, Ohio 43210, United States
| | - Pranay Agarwal
- Department of Biomedical Engineering, Comprehensive Cancer Center, Davis Heart and Lung
Research Institute, and Division of Cardiovascular Medicine,
and Department of Veterinary
Biosciences, The Ohio State University, Columbus, Ohio 43210, United States
| | - Yichao Xiao
- Department of Biomedical Engineering, Comprehensive Cancer Center, Davis Heart and Lung
Research Institute, and Division of Cardiovascular Medicine,
and Department of Veterinary
Biosciences, The Ohio State University, Columbus, Ohio 43210, United States
- Department of Burns and Plastic Surgery, The Third
Xiangya Hospital and Department of Cardiology,
The Second Xiangya Hospital, Central South
University, Changsha, Hunan 410013, P.R. China
| | - Hao Peng
- Department of Biomedical Engineering, Comprehensive Cancer Center, Davis Heart and Lung
Research Institute, and Division of Cardiovascular Medicine,
and Department of Veterinary
Biosciences, The Ohio State University, Columbus, Ohio 43210, United States
- Department of Burns and Plastic Surgery, The Third
Xiangya Hospital and Department of Cardiology,
The Second Xiangya Hospital, Central South
University, Changsha, Hunan 410013, P.R. China
| | - Shuting Zhao
- Department of Biomedical Engineering, Comprehensive Cancer Center, Davis Heart and Lung
Research Institute, and Division of Cardiovascular Medicine,
and Department of Veterinary
Biosciences, The Ohio State University, Columbus, Ohio 43210, United States
| | - Xuanyou Liu
- Department of Biomedical Engineering, Comprehensive Cancer Center, Davis Heart and Lung
Research Institute, and Division of Cardiovascular Medicine,
and Department of Veterinary
Biosciences, The Ohio State University, Columbus, Ohio 43210, United States
| | - Shenghua Zhou
- Department of Burns and Plastic Surgery, The Third
Xiangya Hospital and Department of Cardiology,
The Second Xiangya Hospital, Central South
University, Changsha, Hunan 410013, P.R. China
| | - Jianrong Li
- Department of Biomedical Engineering, Comprehensive Cancer Center, Davis Heart and Lung
Research Institute, and Division of Cardiovascular Medicine,
and Department of Veterinary
Biosciences, The Ohio State University, Columbus, Ohio 43210, United States
| | - Zhenguo Liu
- Department of Biomedical Engineering, Comprehensive Cancer Center, Davis Heart and Lung
Research Institute, and Division of Cardiovascular Medicine,
and Department of Veterinary
Biosciences, The Ohio State University, Columbus, Ohio 43210, United States
| | - Xiaoming He
- Department of Biomedical Engineering, Comprehensive Cancer Center, Davis Heart and Lung
Research Institute, and Division of Cardiovascular Medicine,
and Department of Veterinary
Biosciences, The Ohio State University, Columbus, Ohio 43210, United States
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Hwang DS, Waite JH. Three intrinsically unstructured mussel adhesive proteins, mfp-1, mfp-2, and mfp-3: analysis by circular dichroism. Protein Sci 2012; 21:1689-95. [PMID: 22915553 DOI: 10.1002/pro.2147] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2012] [Revised: 08/15/2012] [Accepted: 08/16/2012] [Indexed: 11/10/2022]
Abstract
Mussel foot proteins (mfps) mediate fouling by the byssal holdfast and have been extensively investigated as models for versatile polymer-mediated underwater adhesion and coatings. However, insights into the structural properties of mfps have lagged far behind the nanomechanical advances, owing in part to the inability of these proteins to crystallize as well as their limited solubility. Here, solution secondary structures of mfp-1, mfp-2, and mfp-3, localized in the mussel byssal cuticle, adhesive plaque, and plaque-substratum interface, respectively, were investigated using circular dichroism. All three have significant extended coil solution structure, but two, mfp-1 and mfp-2, appear to have punctuated regions of structure separated by unstructured domains. Apart from its punctuated distribution, the structure in mfp-1 resembles other structural proteins such as collagen and plant cell-wall proteins with prominent polyproline II helical structure. As in collagen, PP II structure of mfp-1 is incrementally disrupted by increasing the temperature and by raising pH. However, no recognizable change in mfp-1's PP II structure was evident with the addition with Ca²⁺ and Fe³⁺. In contrast, mfp-2 exhibits Ca²⁺- and disulfide-stabilized epidermal growth factor-like domains separated by unstructured sequence. Mfp-2 showed calcium-binding ability. Bound calcium in mfp-2 was not removed by chelation at pH 5.5, but it was released upon reduction of disulfide bonds. Mfp-3, in contrast, appears to consist largely of unstructured extended coils.
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Affiliation(s)
- Dong Soo Hwang
- POSTECH Ocean Science and Technology Institute and School of Environmental Science and Engineering, Pohang University of Science and Technology, Hyoja-Dong, Nam-Gu, Pohang, Gyeongbuk 790-784, Korea.
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Liu Y, Annis DS, Mosher DF. Interactions among the epidermal growth factor-like modules of thrombospondin-1. J Biol Chem 2009; 284:22206-22212. [PMID: 19531495 PMCID: PMC2755945 DOI: 10.1074/jbc.m109.026120] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Epidermal growth factor (EGF)-like modules are defined in part by six cysteines joined by disulfides in a 1–3, 2–4, and 5–6 pattern. Thrombospondin-1 (TSP-1) is a multimodular glycoprotein with three EGF-like modules, E1, E2, and E3, arranged in tandem. These modules likely propagate conformational changes between surrounding C-terminal and N-terminal elements of TSP-1 and interact with other extracellular molecules. E1, E2, and their homologs in other TSPs are unique among EGF-like modules in having two residues rather than one between Cys-4 and Cys-5. In addition, E2 has a calcium-binding site and an unusually long loop between Cys-5 and Cys-6. The structure of E1, E2, or E3 expressed alone changed little upon heating as monitored by far-UV CD, whereas more marked changes occurred in E12, E23, and E123 tandem constructs. The individual modules denatured in differential scanning calorimetry experiments only at >85 °C. E12, E23, or E123 tandem constructs, however, had a transition in the range of 44–70 °C. The temperature of the transition was higher when calcium was present and higher with E123 than with E12 or E23. Isothermal titration calorimetry demonstrated KD values of binding of calcium to E2, E12, E23, or E123 at 25 °C of 11.5, 2.9, 2.2, or 0.3 μm, respectively. Monoclonal antibodies HB8432 and C6.7, which recognize epitopes in E2, bound to E12, E23, or E123 with greater affinity than to E2 alone. These results indicate that interactions among the modules of E123 influence the tertiary structure and calcium binding of E2.
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Affiliation(s)
- Yuanyuan Liu
- Departments of Biomolecular Chemistry and Medicine, University of Wisconsin, Madison, Wisconsin 53706
| | - Douglas S Annis
- Departments of Biomolecular Chemistry and Medicine, University of Wisconsin, Madison, Wisconsin 53706
| | - Deane F Mosher
- Departments of Biomolecular Chemistry and Medicine, University of Wisconsin, Madison, Wisconsin 53706
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Alewood D, Nielsen K, Alewood PF, Craik DJ, Andrews P, Nerrie M, White S, Domagala T, Walker F, Rothacker J, Burgess AW, Nice EC. The role of disulfide bonds in the structure and function of murine epidermal growth factor (mEGF). Growth Factors 2005; 23:97-110. [PMID: 16019431 DOI: 10.1080/08977190500096061] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
A systematic study using solid phase peptide synthesis has been undertaken to examine the role of the disulfide bonds in the structure and function of mEGF. A combination of one, two and three native disulfide pair analogues of an active truncated (4-48) form of mEGF have been synthesised by replacing specific cysteine residues with isosteric a-amino-n-butyric acid (Abu). Oxidation of the peptides was performed using either conventional aerobic oxidation at basic pH, in DMSO under acidic conditions or via selective disulfide formation using orthogonal protection of the cysteine pairs. The contribution of individual, or pairs of, disulfide bonds to EGF structure was evaluated by CD and (1)H-NMR spectroscopy. The mitogenic activity of each analogue was determined using Balb/c 3T3 mouse fibroblastsAs we have reported previously (Barnham et al. 1998), the disulfide bond between residues 6 and 20 can be removed with significant retention of biological activity (EC50 20-50 nM). The overall structure of this analogue was similar to that of native mEGF, indicating that the loss of the 6-20 disulfide bridge did not affect the global fold of the molecule. We now show that removal of any other disulfide bond, either singly or in pairs, results in a major disruption of the tertiary structure, and a large loss of activity (EC50>900 nM). Remarkably, the linear analogue appears to have greater activity (EC50 580 nM) than most one and two disulfide bond analogues although it does not have a definable tertiary structure.
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Affiliation(s)
- Dianne Alewood
- The Institute for Molecular Bioscience, The University of Queensland, Australia
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Yang CH, Wu PC, Huang YB, Tsai YH. A New Approach for Determining the Stability of Recombinant Human Epidermal Growth Factor by Thermal Fourier Transform Infrared (FTIR) Microspectroscopy. J Biomol Struct Dyn 2004; 22:101-10. [PMID: 15214810 DOI: 10.1080/07391102.2004.10506985] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Based on Fourier transform infrared (FTIR) microspectroscopy, the conformation of rhEGF under the influence of pH, heat treatment, chaotropic salts, concentration of salt and protein structure perturbants was studied. The FTIR spectrum of rhEGF showed that major secondary structures from amide I bands composed of 40.6% beta-sheets, 25.0% reverse turns, 16.5% random coils, 13.0% loops and 4.9% side-chain structures. At extreme pH conditions (pH < 4 and pH > 8), there were changes in intensity of the bands attributed to loop (1658 cm(-1)) and random coil structures, and these bands shifted to lower wavenumbers, indicating changes in protein conformation. Thermal denaturation of rhEGF occurred at 40-76 degrees C and the formation of intermolecular beta-aggregates was revealed by the FTIR spectra. Thermal-irreversible property of rhEGF after second-heating treatment suggested that rhEGF has a poor thermal stability. While investigating the stability of rhEGF in the presence of chaotropic salts, anions induced protein unfolding of rhEGF more significantly than cations. The optimal stabilizing effect was found at the 2 M NaCl added to rhEGF, and expressed the structure of rhEGF more stable on the many components. The bands of loop structure (1654 cm(-1)), beta-sheet (1638 cm(-1)) and intermolecular antiparallel beta-aggregation formation (1694, 1619 and 1612 cm(-1)) seem to be "marked" to be more sensitive in determining environmental changes of rhEGF for FTIR microspectroscopy.
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Affiliation(s)
- C-H Yang
- Graduate Institute of Pharmaceutical Sciences, Kaohsiung Medical University, No. 100 Shih-Chuan 1st Road, Kaohsiung 807, Taiwan, R.O.C.
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Li T, Yamane H, Arakawa T, Narhi LO, Philo J. Effect of the intermolecular disulfide bond on the conformation and stability of glial cell line-derived neurotrophic factor. Protein Eng Des Sel 2002; 15:59-64. [PMID: 11842239 DOI: 10.1093/protein/15.1.59] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Glial cell line-derived neurotrophic factor (GDNF) is a member of the TGF-beta superfamily of proteins. It exists as a covalent dimer in solution, with the 15 kDa monomers linked by an interchain disulfide bond through the Cys101 residues. Sedimentation equilibrium and velocity experiments demonstrated that, after removal of the interchain disulfide bond, GDNF remains as a non-covalent dimer and is stable at pH 7.0. To investigate the effect of the intermolecular disulfide on the structure and stability of GDNF, we compared the solution structures of the wild-type protein and a cysteine-101 to alanine (C101A) mutant using Fourier transform infrared (FTIR), FT-Raman and circular dichroism (CD) spectroscopy and sedimentation analysis. The elimination of the intermolecular disulfide bond causes only minor changes (approximately 4%) in the secondary structures of GDNF. The far- and near-UV CD spectra demonstrated that the secondary and tertiary structures were similar for both wild-type and C101A GDNF. Heparin binding and sedimentation velocity experiments also indicated that the folded structure of the wild-type and C101A GDNF are indistinguishable. The thermal stability of GDNF does not appear to be affected by the absence of the interchain disulfide bond and the biological activity of the C101A mutant is identical with that of the wild-type protein. However, small but significant changes in side chain conformations of tyrosine and aliphatic residues were observed by FT-Raman spectroscopy upon removal of the intermolecular disulfide bond, which may reflect structural changes in the area of dimeric contact. By comparing the Raman spectrum of wild-type GDNF with that of the C101A analog, we identified the conformation of the intermolecular disulfide as trans-gauche-trans geometry. These results indicate that GDNF is an active, properly folded molecule in the absence of the interchain disulfide bond.
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Affiliation(s)
- Tiansheng Li
- Pharmaceutics, Amgen Inc., Amgen Center, One Amgen Drive,M/S 8-1-C Thousand Oaks, CA 91320, USA
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Dukor RK, Pancoska P, Keiderling TA, Prestrelski SJ, Arakawa T. Vibrational circular dichroism studies of epidermal growth factor and basic fibroblast growth factor. Arch Biochem Biophys 1992; 298:678-81. [PMID: 1416996 DOI: 10.1016/0003-9861(92)90465-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Vibrational circular dichroism (VCD) studies are reported for two unrelated recombinant growth factor proteins: epidermal growth factor and basic fibroblast growth factor (bFGF). NMR, electronic CD, and bFGF X-ray studies indicate that these two proteins are primarily composed of beta-sheet and loop secondary structure elements with no detectable alpha-helices. Two reports on solution conformation of these proteins using FTIR absorption spectroscopy with subsequent resolution enhancement confirmed the presence of a large fraction of a beta-sheet conformation but in addition indicated the presence of large absorption bands in the 1650-1656 cm-1 region, which are typically assigned to alpha-helices. The VCD spectra of both proteins have band shapes that strongly resemble those of other high beta-sheet fraction proteins, such as the trypsin family of proteins. Quantitative analysis of the VCD spectra also indicates that these proteins are predominantly in beta-sheet and extended ("other") conformations with very little alpha-helix fraction. These results agree with the CD interpretation and affirm that the FTIR peaks in the region 1650-1656 cm-1 can be assigned to loops. This study provides an example of the limitations of using FTIR frequencies alone for examination of protein secondary structure.
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Affiliation(s)
- R K Dukor
- Department of Chemistry, University of Illinois, Chicago 60680
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