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Ahmad M, Bushra R, Ritzoulis C. Pectin-mucin interactions: Insights from fluorimetry, thermodynamics and dual (static and dynamic) quenching mechanisms. Int J Biol Macromol 2024; 277:134564. [PMID: 39116979 DOI: 10.1016/j.ijbiomac.2024.134564] [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: 03/26/2024] [Revised: 08/05/2024] [Accepted: 08/05/2024] [Indexed: 08/10/2024]
Abstract
Binary systems of citrus peel pectin (a major food carbohydrate) and mucin (a principal oral-gastrointestinal glycoprotein) are studied, as to understand the interactions and thermodynamics between food and biofluids during oral processing and digestion. The fluorimetry emission spectra of mucin were quenched by pectin addition at 293, 301, 310 and 318 K, indicating direct contact between the two macromolecular populations. A red shift, suggesting pectin-induced alterations on mucin conformation, has been observed at 318 K. Intensity-based Stern - Volmer plots fitted second-order polynomial equations, suggesting the coexistence of both static and dynamic quenching, while the increase of the slopes with temperature points to the predominance of dynamic phenomena. Time-resolved fluorescence measurements also point to dynamic quenching related to transient interactions, rather than to specific bonding. Thermodynamic analysis yields negative free energy changes in all cases, with positive changes for enthalpy and large positive values for TΔS. These are in agreement with the Stern - Volmer analysis, suggesting the predominance of transient, dynamic (here entropic) interactions. These provide an image of mucin interacting with pectin macromolecules during the oral processing and digestion of foods, and can relate to the texture, flavor (e.g. astringency) and bioavailability of polysaccharide-based foods.
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Affiliation(s)
- Mehraj Ahmad
- Joint International Research Lab of Lignocellulosic Functional Materials and Provincial Key Lab of Pulp and Paper Sci. & Tech., Nanjing Forestry University, Nanjing 210037, Jiangsu, China; Department of Food Science and Engineering, College of Light Industry and Food, Nanjing Forestry University, Nanjing 210037, Jiangsu, China
| | - Rani Bushra
- Joint International Research Lab of Lignocellulosic Functional Materials and Provincial Key Lab of Pulp and Paper Sci. & Tech., Nanjing Forestry University, Nanjing 210037, Jiangsu, China; Department of Food Science and Engineering, College of Light Industry and Food, Nanjing Forestry University, Nanjing 210037, Jiangsu, China
| | - Christos Ritzoulis
- Department of Food Science and Technology, International Hellenic University, Alexander Campus, 57400 Thessaloniki, Greece.
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Cho YJ, Kim H, Lim SI. Preserved structure and function of human serum albumin self-folded in the oxidative cytoplasm of Escherichia coli. J Biotechnol 2024; 390:62-70. [PMID: 38761885 DOI: 10.1016/j.jbiotec.2024.05.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2024] [Revised: 04/11/2024] [Accepted: 05/07/2024] [Indexed: 05/20/2024]
Abstract
Human serum albumin (HSA), a polypeptide featuring 17 disulfide bonds, acts as a crucial transport protein in human blood plasma. Its extended circulation half-life, mediated by FcRn (neonatal Fc receptor)-facilitated recycling, positions HSA as an excellent carrier for long-acting drug delivery. However, the conventional method of obtaining HSA from human blood faces limitations due to availability and potential contamination risks, such as blood-borne diseases. This study introduced SHuffle, an oxidative Escherichia coli (E. coli) expression system, for the production of recombinant HSA (rHSA) that spontaneously self-folds into its native conformation. This system ensures precise disulfide bond formation and correct folding of cysteine-rich rHSA, eliminating the need for chaperone co-expression or domain fusion of a folding enhancer. The purified rHSA underwent thorough physicochemical characterization, including mass spectrometry, circular dichroism spectroscopy, intrinsic fluorescence spectroscopy, esterase-like activity assay, and size exclusion chromatography, to assess critical quality attributes. Importantly, rHSA maintained native binding affinity to FcRn and the albumin-binding domain. Collectively, our analyses demonstrated a high comparability between rHSA and plasma-derived HSA. The expression of rHSA in E. coli with an oxidizing cytosol provides a secure and cost-effective approach, enhancing the potential of rHSA for diverse medical applications.
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Affiliation(s)
- Yong Joon Cho
- Department of Chemical Engineering, Pukyong National University, Yongso-ro 45, Nam-gu, Busan, Republic of Korea
| | - Hyunji Kim
- Department of Chemical Engineering, Pukyong National University, Yongso-ro 45, Nam-gu, Busan, Republic of Korea
| | - Sung In Lim
- Department of Chemical Engineering, Pukyong National University, Yongso-ro 45, Nam-gu, Busan, Republic of Korea.
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Torrez M, Brajanovska A, Slowinska K. Selective Excitation of the 1L α State of Tryptophan in Collagen-like Peptides Can Reveal the Formation of a Heterotrimer. ACS OMEGA 2024; 9:29848-29856. [PMID: 39005791 PMCID: PMC11238237 DOI: 10.1021/acsomega.4c03600] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/14/2024] [Revised: 06/06/2024] [Accepted: 06/17/2024] [Indexed: 07/16/2024]
Abstract
Fluorescence emission from tryptophan residues has been often used to probe the protein structure due to its transition dipole moment sensitivity to the local environment. We report the fluorescence study of a collagen-like peptide heterotrimer modified with the tryptophan in the X position (X-Y-Gly) n that shows the diminished fluorescence in a homotrimer versus a heterotrimer when the 1Lα state is selectively excited. This behavior is only observed in folded peptides, below the helix-to-coil transition temperature, and can be explained by long-range interactions between the tryptophans located on different strands within the triple helix, not by the change in the local environment. Our results suggest that tryptophan homotransfer is possible at distances much longer than the R 0 (0.5-0.7 nm) previously estimated. These observations imply that the energy transfer between the 1Lα states of proximal tryptophans can be facilitated by constraining their rotation by the helix and, thus, can be employed as a reporter of heterotrimer formation in biosensors.
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Affiliation(s)
- Miriam Torrez
- Department of Chemistry and Biochemistry, California State University Long Beach, 1250 Bellflower Blvd., Long Beach, California 90840, United States
| | - Aleksandra Brajanovska
- Department of Chemistry and Biochemistry, California State University Long Beach, 1250 Bellflower Blvd., Long Beach, California 90840, United States
| | - Katarzyna Slowinska
- Department of Chemistry and Biochemistry, California State University Long Beach, 1250 Bellflower Blvd., Long Beach, California 90840, United States
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Khrustalev VV, Stojarov AN, Akunevich AA, Baranov OE, Popinako AV, Samoilovich EO, Yermalovich MA, Semeiko GV, Sapon EG, Cheprasova VI, Shalygo NV, Poboinev VV, Khrustaleva TA, Khrustaleva OV. Structural Shifts of the Parvovirus B19 Capsid Receptor-binding Domain: A Peptide Study. Protein Pept Lett 2024; 31:128-140. [PMID: 38053353 DOI: 10.2174/0109298665272845231121064717] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Revised: 09/25/2023] [Accepted: 11/07/2023] [Indexed: 12/07/2023]
Abstract
BACKGROUND Binding appropriate cellular receptors is a crucial step of a lifecycle for any virus. Structure of receptor-binding domain for a viral surface protein has to be determined before the start of future drug design projects. OBJECTIVES Investigation of pH-induced changes in the secondary structure for a capsid peptide with loss of function mutation can shed some light on the mechanism of entrance. METHODS Spectroscopic methods were accompanied by electrophoresis, ultrafiltration, and computational biochemistry. RESULTS In this study, we showed that a peptide from the receptor-binding domain of Parvovirus B19 VP1 capsid (residues 13-31) is beta-structural at pH=7.4 in 0.01 M phosphate buffer, but alpha- helical at pH=5.0, according to the circular dichroism (CD) spectroscopy results. Results of infra- red (IR) spectroscopy showed that the same peptide exists in both alpha-helical and beta-structural conformations in partial dehydration conditions both at pH=7.4 and pH=5.0. In contrast, the peptide with Y20W mutation, which is known to block the internalization of the virus, forms mostly alpha-helical conformation in partial dehydration conditions at pH=7.4. According to our hypothesis, an intermolecular antiparallel beta structure formed by the wild-type peptide in its tetramers at pH=7.4 is the prototype of the similar intermolecular antiparallel beta structure formed by the corresponding part of Parvovirus B19 receptor-binding domain with its cellular receptor (AXL). CONCLUSION Loss of function Y20W substitution in VP1 capsid protein prevents the shift into the beta-structural state by the way of alpha helix stabilization and the decrease of its ability to turn into the disordered state.
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Affiliation(s)
| | | | | | - Oleg Evgenyevich Baranov
- Bach Institute of Biochemistry, Shared-Access Equipment Centre "Industrial Biotechnology" of Russian Academy of Science, Leninskiy prospect, 33/2, Moscow, 119071, Russian Federation
| | - Anna Vladimirovna Popinako
- Bach Institute of Biochemistry, Research Center of Biotechnology of the Russian Academy of Sciences, Leninskiy prospect, 33/2, Moscow, 119071, Russian Federation
| | - Elena Olegovna Samoilovich
- Laboratory of Vaccine-controlled Infections, Republican Research and Practical Center for Epidemiology and Microbiology, Filimonova 23, Minsk, 220114, Belarus
| | - Marina Anatolyevna Yermalovich
- Laboratory of Vaccine-controlled Infections, Republican Research and Practical Center for Epidemiology and Microbiology, Filimonova 23, Minsk, 220114, Belarus
| | - Galina Valeryevna Semeiko
- Laboratory of Vaccine-controlled Infections, Republican Research and Practical Center for Epidemiology and Microbiology, Filimonova 23, Minsk, 220114, Belarus
| | - Egor Gennadyevich Sapon
- Laboratory of infra-red spectroscopy and infra-red microscopy, Belarusian State Technological University, Sverdlova 13a, Minsk, 220006, Belarus
| | - Victoria Igorevna Cheprasova
- Laboratory of infra-red spectroscopy and infra-red microscopy, Belarusian State Technological University, Sverdlova 13a, Minsk, 220006, Belarus
| | | | - Victor Vitoldovich Poboinev
- Department of General Chemistry, Belarusian State Medical University, Dzerzhinskogo 83, Minsk, 220045, Belarus
| | - Tatyana Aleksandrovna Khrustaleva
- Laboratory of Biomedical Technologies and Medical Rehabilitation, Institute of Physiology of the National Academy of Sciences of Belarus, Academicheskaya 28, Minsk, 220072; Belarus
| | - Olga Victorovna Khrustaleva
- Department of General Chemistry, Belarusian State Medical University, Dzerzhinskogo 83, Minsk, 220045, Belarus
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Song Y, Wang Z, Ji H, Jiang Z, Li X, Du Z, Wei S, Sun Y. Fatty acid modification of casein bioactive peptides nano-assemblies, synthesis, characterization and anticarcinogenic effect. Int J Biol Macromol 2024; 254:127718. [PMID: 37918594 DOI: 10.1016/j.ijbiomac.2023.127718] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Revised: 10/24/2023] [Accepted: 10/25/2023] [Indexed: 11/04/2023]
Abstract
In this study, the nano-assemblies of bovine casein hydrolyzed peptides (HP) modified by fatty acids with various alkyl chain lengths (C8, C10, C12 and C14) were synthesized. The physicochemical properties of HP-C8-HP-C14 nano-assemblies were characterized using spectra, laser particle size analyzer, contact angle meter, scanning electron microscope (SEM) and cryo-transmission electron microscope (Cryo-TEM). HP-C8 and HP-C10 self-assembled into a hollow cube cage with an average size of ~500 nm, and the assembly of HP-C12 showed a flower-shaped morphology with more dispersed behavior, and droplet size was observed as ~20 nm. The in vitro cytotoxicity against human breast cancer cells MCF-7 was tested using CCK-8 assay and flow cytometry analysis. HP-C12 showed the highest cytotoxicity for MCF-7 cells with an inhibition rate of 66.03 % ± 0.35 % with an IC50 value of 7.4 μM among HP-Cn. HP-C8, HP-C10 and HP-C12 significantly affected on the migration, invasion and apoptosis of MCF-7 cells. The apoptosis mechanism may depend on the upregulation of anti-apoptotic protein Bcl-2 as well as pro-apoptotic proteins Bax and caspase-8. The dead MCF-7 cells were analyzed with UHPLC-MS/MS using untargeted metabolomics, revealing key metabolic pathways.
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Affiliation(s)
- Yang Song
- College of Vocational and Technical Education, Yunnan Normal University, Kunming, Yunnan, China
| | - Zhichun Wang
- College of Vocational and Technical Education, Yunnan Normal University, Kunming, Yunnan, China
| | - Hang Ji
- College of Vocational and Technical Education, Yunnan Normal University, Kunming, Yunnan, China
| | - Zhongyou Jiang
- College of Vocational and Technical Education, Yunnan Normal University, Kunming, Yunnan, China
| | - Xiujuan Li
- Pharmaceutical Department, The Affiliated Taian City Central Hospital of Qingdao University, Taian, 271000, China
| | - Zhongyao Du
- College of Vocational and Technical Education, Yunnan Normal University, Kunming, Yunnan, China
| | - Song Wei
- Tumor Precise Intervention and Translational Medicine Laboratory, The Affiliated Taian City Central Hospital of Qingdao University, Taian, 271000, China.
| | - Yang Sun
- College of Vocational and Technical Education, Yunnan Normal University, Kunming, Yunnan, China.
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Khan S, Naeem A. Bovine serum albumin prevents human hemoglobin aggregation and retains its chaperone-like activity. J Biomol Struct Dyn 2024; 42:346-361. [PMID: 36974939 DOI: 10.1080/07391102.2023.2192802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Accepted: 03/13/2023] [Indexed: 03/29/2023]
Abstract
This study investigates the ability of bovine serum albumin (BSA) to act as an extracellular chaperone (EC) on human hemoglobin (Hb) at a pH of 7.4. The best temperature for studying this behavior was determined by analyzing Hb's aggregation kinetics at multiple temperatures. 55 °C was chosen as the optimal temperature for forming Hb amyloids. BSA was then tested at various concentrations (20-100 μM) to assess its chaperone-like activity on Hb at 55 °C. At a concentration of 100 μM, BSA exhibits chaperone-like activity with a client protein:BSA ratio of 1:10. The high ratio implies that the chaperone activity of BSA is favored by the effects of macromolecular crowding. The results showed that BSA has the potential to inhibit Hb's dissociation into alpha and beta subunits and protein aggregation by inhibiting secondary nucleation. BSA also causes the depolymerization of fibrils over time. The results were validated using molecular docking and all-atom molecular dynamics simulations. MD analysis such as RMSD, RMSF, Rg, SASA, Hydrogen bond, PCA, Free energy landscape (FEL) revealed that the stability of hemoglobin is greater when it is bound to BSA compared to unbound state. The study suggests that BSA can potentially bind to Hb dimers and reduce excitonic interactions, which reduces Hb aggregation. These results are consistent with the aggregation kinetics experiments.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Sadaf Khan
- Department of Biochemistry, Aligarh Muslim University, Aligarh, India
| | - Aabgeena Naeem
- Department of Biochemistry, Aligarh Muslim University, Aligarh, India
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Poboinev VV, Khrustalev VV, Akunevich AA, Shalygo NV, Stojarov AN, Khrustaleva TA, Kordyukova LV. Peptide Models of the Cytoplasmic Tail of Influenza A/H1N1 Virus Hemagglutinin Expand Understanding its pH-Dependent Modes of Interaction with Matrix Protein M1. Protein J 2023:10.1007/s10930-023-10101-z. [PMID: 36952102 PMCID: PMC10034248 DOI: 10.1007/s10930-023-10101-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/27/2023] [Indexed: 03/24/2023]
Abstract
Influenza A virus hemagglutinin (HA) is a major virus antigen. No cryo-electron microscopy or X-ray data can be obtained for the HA intraviral (cytoplasmic) domain (CT) post-translationally modified with long fatty acid residues bound to three highly conserved cysteines. We recently proposed a model of HA CT of Influenza A/H1N1 virus possessing an antiparallel beta structure based on the experimental secondary structure analysis of four 14-15 amino acid long synthetic peptides, corresponding to the HA CT sequence, with free or acetaminomethylated cysteines. To dispel doubts about possible non-specific "amyloid-like" aggregation of those synthetic peptides in phosphate buffer solution, we have determined the order of oligomers based on blue native gel electrophoresis, membrane filtration, fluorescence spectroscopy and molecular modeling approaches. We have found that unmodified peptides form only low molecular weight oligomers, while modified peptides form both oligomers of low order similar to those found for unmodified peptides and high order conglomerates, which however are not of beta-amyloid-like fold. This study confirms that the beta structure previously detected by circular dichroism spectroscopy analysis is more likely the result of intrinsic propensity of the HA CT amino acid sequence than the consequence of aggregation. The structures of low order oligomers of the synthetic peptides were used for in silico experiments on modeling of HA CT interactions with matrix protein M1 at physiological and acidic pH levels and revealed two different areas of binding. Finally, tripeptides capable of blocking interactions between HA CT and M1 were proposed.
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Queiroz N, Mendes C, Nascimento J, Silva M, Oliveira JE, BEZERRA DE OLIVEIRA SEVERINOCARLOS. OXIDATION MECHANISM OF 1‐METHYL‐TRYPTOPHAN AND TRYPTOPHAN ON GLASSY CARBON ELECTRODE: A COMPARATIVE STUDY. ELECTROANAL 2022. [DOI: 10.1002/elan.202200249] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Cho KH, Kim JH, Nam HS, Kang DJ. Efficacy Comparison Study of Human Epidermal Growth Factor (EGF) between Heberprot-P® and Easyef® in Adult Zebrafish and Embryo under Presence or Absence Combination of Diabetic Condition and Hyperlipidemia to Mimic Elderly Patients. Geriatrics (Basel) 2022; 7:geriatrics7020045. [PMID: 35447848 PMCID: PMC9028627 DOI: 10.3390/geriatrics7020045] [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: 03/05/2022] [Revised: 04/02/2022] [Accepted: 04/02/2022] [Indexed: 12/30/2022] Open
Abstract
Recombinant human epidermal growth factor (EGF) has been used to treat adult diabetic foot ulcers and pediatric burns by facilitating wound healing and epithelization, especially for elderly patients. Several formulation types of EGF from different expression hosts are clinically available, such as intralesional injection and topical application. On the other hand, no study has compared the in vivo efficacy of EGF products directly in terms of tissue regeneration and wound healing activity. The present study compared two commercial products, Heberprot-P75® and Easyef®, in terms of their tissue regeneration activity in adult zebrafish and the developmental speed of zebrafish embryos. Fluorescence spectroscopy showed that the two EGF products had different Trp fluorescence emission spectra: Easyef® showed a wavelength of maximum fluorescence (WMF) of 337 nm with weak fluorescence intensity (FI), while Heberprot-P75® showed WMF of 349 nm with a 4.1 times stronger FI than that of Easyef®. The WMF of Heberprot-P75® was quenched by adding singlet oxygen in ozonated oil, while the WMF of Easyef® was not quenched. Treatment with Heberprot-P75® induced greater embryo development speed with a higher survival rate after exposure to EGF in water and microinjection into embryos. Under normal diet (ND) consumption, Heberprot-P75® showed a 1.4 times higher tail fin regeneration activity than Easyef® during seven days from the intraperitoneal injection (10 μL, 50 μg/mL) after amputating the tail fin. Under ND consumption and diabetic condition caused by streptozotocin (STZ) treatment, Heberprot-P75® showed 2.1 times higher tail fin regeneration activity than Easyef® from the same injection and amputation protocol. Under a high-cholesterol diet (HCD) alone, Heberprot-P75® showed 1.2 times higher tail fin regeneration activity than the Easyef® group and PBS group from the same injection and amputation. Under diabetic conditions (STZ-injected) and HCD consumption, the Heberprot-P75® group showed 1.7 and 1.5 times higher tail fin regeneration activity than the Easyef® group and PBS group, respectively, with a distinct and clean regeneration pattern. In contrast, the Easyef® group and PBS group showed ambiguous regeneration patterns with a severe fissure of the tail fin, which is a typical symptom of a diabetic foot. In conclusion, Heberprot-P75® and Easyef® have different Trp fluorescence properties in terms of the WMF and fluorescence quenching. Treatment of Heberprot-P75® induced a greater developmental speed of zebrafish embryos in both water exposure and microinjection. Heberprot-P75® induced significantly higher wound healing and tissue regeneration activity than Easyef® and PBS in the presence or absence of diabetic conditions and cholesterol supplementation.
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Affiliation(s)
- Kyung-Hyun Cho
- Raydel Research Institute, Medical Innovation Complex, Daegu 41061, Korea; (J.-H.K.); (H.-S.N.); (D.-J.K.)
- LipoLab, Yeungnam University, Gyeongsan 38541, Korea
- Correspondence: ; Tel.: +82-53-964-1990; Fax: +82-53-965-1992
| | - Ju-Hyun Kim
- Raydel Research Institute, Medical Innovation Complex, Daegu 41061, Korea; (J.-H.K.); (H.-S.N.); (D.-J.K.)
| | - Hyo-Seon Nam
- Raydel Research Institute, Medical Innovation Complex, Daegu 41061, Korea; (J.-H.K.); (H.-S.N.); (D.-J.K.)
| | - Dae-Jin Kang
- Raydel Research Institute, Medical Innovation Complex, Daegu 41061, Korea; (J.-H.K.); (H.-S.N.); (D.-J.K.)
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Equilibrium Between Dimeric and Monomeric Forms of Human Epidermal Growth Factor is Shifted Towards Dimers in a Solution. Protein J 2022; 41:245-259. [PMID: 35348971 DOI: 10.1007/s10930-022-10051-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/22/2022] [Indexed: 10/18/2022]
Abstract
An interplay between monomeric and dimeric forms of human epidermal growth factor (EGF) affecting its interaction with EGF receptor (EGFR) is poorly understood. While EGF dimeric structure was resolved at pH 8.1, the possibility of EGF dimerization under physiological conditions is still unclear. This study aimed to describe the oligomeric state of EGF in a solution at physiological pH value. With centrifugal ultrafiltration followed by blue native gel electrophoresis, we showed that synthetic human EGF in a solution at a concentration of 0.1 mg/ml exists mainly in the dimeric form at pH 7.4 and temperature of 37 °C, although a small fraction of its monomers was also observed. Based on bioinformatics predictions, we introduced the D46G substitution to examine if EGF C-terminal part is directly involved in the intermolecular interface formation of the observed dimers. We found a reduced ability of the resulting EGF D46G dimers to dissociate at temperatures up to 50 °C. The D46G substitution also increased the intermolecular antiparallel β-structure content within the EGF peptide in a solution according to the CD spectra analysis that was confirmed by HATR-FTIR results. Additionally, the energy transfer between Tyr and Trp residues was detected by fluorescence spectroscopy for the EGF D46G mutant, but not for the native EGF. This allowed us to suggest the elongation and rearrangement of the intermolecular β-structure that leads to the observed stabilization of EGF D46G dimers. The results imply EGF dimerization under physiological pH value and temperature and the involvement of EGF C-terminal part in this process.
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