Unfolding pathway of myoglobin. Evidence for a multistate process.
Abstract: The free energy of unfolding of horse myoglobin has been calculated from the denaturation pattern induced by guanidine hydrochloride as well as by acid. The delta GH2O, i.e., the value in the absence of denaturant obtained by using the two-state transition model, was found to be 25% lower than that determined from the acid denaturation pattern, i.e., 12.0 kcal/mol, although the extent of protein denaturation produced by acid was much lower. The amount of helical structure surviving the acid-induced conformational change was estimated to be 50% of that present in the native protein, and it could be destroyed only after exposure of myoglobin samples kept at pH 3.0 to concentrated guanidine. From the guanidine denaturation pattern at acidic pH, a further variation of free energy of unfolding of 5.5 kcal/mol could be calculated, thus indicating that the overall free energy of unfolding determined from the two consecutive processes corresponds to 17.5 kcal/mol. The discrepancy between the two sets of data, i.e., guanidine unfolding at neutral pH and acid unfolding followed by addition of denaturant, has been considered to depend on the general assumption that the guanidine unfolding of myoglobin is a two-state process in the transition region. According to the recent experimental evidence showing the occurrence of at least two molecular events during the guanidine unfolding of apomyoglobin [Colonna, G., Balestrieri, C., Bismuto, E., Servillo, L., & Irace, G. (1982) Biochemistry 21, 212-215], the guanidine denaturation pattern of myoglobin was analyzed in terms of two independent steps.(ABSTRACT TRUNCATED AT 250 WORDS)
Publication Date: 1983-08-30 PubMed ID: 6626499DOI: 10.1021/bi00287a001Google Scholar: Lookup
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- Journal Article
Summary
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This research investigates the process and energy involved in the unfolding of the protein myoglobin. It finds that the unfolding process is more complex than previously thought and factors such as guanidine hydrochloride and acid can affect the free energy of unfolding.
Research Objective and Methodology
- The study set out to explore the unfolding process of horse myoglobin. The chemical reactions induced by denaturing agents such as guanidine hydrochloride and acid were examined to fully understand how myoglobin unfolds.
- The researchers calculated the change in free energy of unfolding (delta GH2O) using a two-state transition model. This calculation was carried out r both in the absence of a denaturing agent and when induced by acid.
Key Findings
- The free energy of unfolding was found to be 25% lower when derived from the acid denaturation pattern (12.0 kcal/mol) than when calculated in the absence of the denaturing agent. This was despite the fact that the extent of protein denaturation produced by acid was significantly less.
- The scientists were able to deduce that 50% of the helical structure survived the acid-induced change. However, this could be destroyed when myoglobin samples were exposed to concentrated guanidine at a pH level of 3.0.
- Further examination revealed a variation in the free energy of unfolding at acidic pH, of around 5.5 kcal/mol. The total free energy of unfolding, calculated from the two consecutive processes, corresponded to 17.5 kcal/mol.
Conclusions
- The study theorizes that the discrepancies observed in the data could be attributed to the assumptions that myoglobin unfolds solely as a two-state process. It proposes that the unfolding process is more multi-state in nature, involving at least two molecular events.
- These findings are corroborated by recent experimental evidence from other researchers who found similar complexities in the unfolding of apomyoglobin.
Cite This Article
APA
Bismuto E, Colonna G, Irace G.
(1983).
Unfolding pathway of myoglobin. Evidence for a multistate process.
Biochemistry, 22(18), 4165-4170.
https://doi.org/10.1021/bi00287a001 Publication
Researcher Affiliations
MeSH Terms
- Animals
- Guanidine
- Guanidines
- Horses
- Hydrogen-Ion Concentration
- Kinetics
- Mathematics
- Myoglobin / metabolism
- Protein Conformation
- Thermodynamics
Citations
This article has been cited 12 times.- Frankenfield K, Marchany-Rivera D, Flanders KG, Cruz-Balberdy A, Lopez-Garriga J, Cerda JF. Fluoride binding to characteristic heme-pocket centers: Insights into ligand stability.. J Inorg Biochem 2021 Nov;224:111578.
- Lee JG, Lannigan K, Shelton WA, Meissner J, Bharti B. Adsorption of Myoglobin and Corona Formation on Silica Nanoparticles.. Langmuir 2020 Dec 1;36(47):14157-14165.
- Iyer LK, Moorthy BS, Topp EM. Photolytic Cross-Linking to Probe Protein-Protein and Protein-Matrix Interactions in Lyophilized Powders.. Mol Pharm 2015 Sep 8;12(9):3237-49.
- Singh R, Hassan MI, Islam A, Ahmad F. Cooperative Unfolding of Residual Structure in Heat Denatured Proteins by Urea and Guanidinium Chloride.. PLoS One 2015;10(6):e0128740.
- Iannuzzi C, Irace G, Sirangelo I. The effect of glycosaminoglycans (GAGs) on amyloid aggregation and toxicity.. Molecules 2015 Feb 2;20(2):2510-28.
- Zhang C, Gao C, Mu J, Qiu Z, Li L. Spectroscopic studies on unfolding processes of apo-neuroglobin induced by guanidine hydrochloride and urea.. Biomed Res Int 2013;2013:349542.
- Vilasi S, Sarcina R, Maritato R, De Simone A, Irace G, Sirangelo I. Heparin induces harmless fibril formation in amyloidogenic W7FW14F apomyoglobin and amyloid aggregation in wild-type protein in vitro.. PLoS One 2011;6(7):e22076.
- Droghetti E, Sumithran S, Sono M, Antalík M, Fedurco M, Dawson JH, Smulevich G. Effects of urea and acetic acid on the heme axial ligation structure of ferric myoglobin at very acidic pH.. Arch Biochem Biophys 2009 Sep;489(1-2):68-75.
- Clark SM, Konermann L. Diffusion measurements by electrospray mass spectrometry for studying solution-phase noncovalent interactions.. J Am Soc Mass Spectrom 2003 May;14(5):430-41.
- Sinha A, Yadav S, Ahmad R, Ahmad F. A possible origin of differences between calorimetric and equilibrium estimates of stability parameters of proteins.. Biochem J 2000 Feb 1;345 Pt 3(Pt 3):711-7.
- Blum O, Haiek A, Cwikel D, Dori Z, Meade TJ, Gray HB. Isolation of a myoglobin molten globule by selective cobalt(III)-induced unfolding.. Proc Natl Acad Sci U S A 1998 Jun 9;95(12):6659-62.
- Sugawara Y, Matsuoka A, Kaino A, Shikama K. Role of globin moiety in the autoxidation reaction of oxymyoglobin: effect of 8 M urea.. Biophys J 1995 Aug;69(2):583-92.
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