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Miller A, Chia S, Toprakcioglu Z, Hakala T, Schmid R, Feng Y, Kartanas T, Kamada A, Vendruscolo M, Ruggeri FS, Knowles TP. Enhanced surface nanoanalytics of transient biomolecular processes. SCIENCE ADVANCES 2023; 9:eabq3151. [PMID: 36638180 PMCID: PMC9839325 DOI: 10.1126/sciadv.abq3151] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Accepted: 12/13/2022] [Indexed: 06/17/2023]
Abstract
Fundamental knowledge of the physical and chemical properties of biomolecules is key to understanding molecular processes in health and disease. Bulk and single-molecule analytical methods provide rich information about biomolecules but often require high concentrations and sample preparation away from physiologically relevant conditions. Here, we present the development and application of a lab-on-a-chip spray approach that combines rapid sample preparation, mixing, and deposition to integrate with a range of nanoanalytical methods in chemistry and biology, providing enhanced spectroscopic sensitivity and single-molecule spatial resolution. We demonstrate that this method enables multidimensional study of heterogeneous biomolecular systems over multiple length scales by nanoscopy and vibrational spectroscopy. We then illustrate the capabilities of this platform by capturing and analyzing the structural conformations of transient oligomeric species formed at the early stages of the self-assembly of α-synuclein, which are associated with the onset of Parkinson's disease.
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Affiliation(s)
- Alyssa Miller
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
| | - Sean Chia
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
| | - Zenon Toprakcioglu
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
| | - Tuuli Hakala
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
| | - Roman Schmid
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
| | - Yaduo Feng
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
| | - Tadas Kartanas
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
| | - Ayaka Kamada
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
| | - Michele Vendruscolo
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
| | - Francesco Simone Ruggeri
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
- Laboratory of Organic Chemistry, Wageningen University and Research, Stippeneng 4, Wageningen, 6703 WE, Netherlands
- Physical Chemistry and Soft Matter, Wageningen University and Research, Stippeneng 4, Wageningen, 6703 WE, Netherlands
| | - Tuomas P. J. Knowles
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK
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2
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Ulyanova V, Nadyrova A, Dudkina E, Kuznetsova A, Ahmetgalieva A, Faizullin D, Surchenko Y, Novopashina D, Zuev Y, Kuznetsov N, Ilinskaya O. Structural and Functional Differences between Homologous Bacterial Ribonucleases. Int J Mol Sci 2022; 23:ijms23031867. [PMID: 35163789 PMCID: PMC8837141 DOI: 10.3390/ijms23031867] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2021] [Revised: 01/28/2022] [Accepted: 02/04/2022] [Indexed: 02/04/2023] Open
Abstract
Small cationic guanyl-preferring ribonucleases (RNases) produced by the Bacillus species share a similar protein tertiary structure with a high degree of amino acid sequence conservation. However, they form dimers that differ in conformation and stability. Here, we have addressed the issues (1) whether the homologous RNases also have distinctions in catalytic activity towards different RNA substrates and interactions with the inhibitor protein barstar, and (2) whether these differences correlate with structural features of the proteins. Circular dichroism and dynamic light scattering assays revealed distinctions in the structures of homologous RNases. The activity levels of the RNases towards natural RNA substrates, as measured spectrometrically by acid-soluble hydrolysis products, were similar and decreased in the row high-polymeric RNA >>> transport RNA > double-stranded RNA. However, stopped flow kinetic studies on model RNA substrates containing the guanosine residue in a hairpin stem or a loop showed that the cleavage rates of these enzymes were different. Moreover, homologous RNases were inhibited by the barstar with diverse efficiency. Therefore, minor changes in structure elements of homologous proteins have a potential to significantly effect molecule stability and functional activities, such as catalysis or ligand binding.
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Affiliation(s)
- Vera Ulyanova
- Department of Microbiology, Institute of Fundamental Medicine and Biology, Kazan (Volga Region) Federal University, 420008 Kazan, Russia; (A.N.); (E.D.); (A.A.); (Y.S.); (O.I.)
- Correspondence:
| | - Alsu Nadyrova
- Department of Microbiology, Institute of Fundamental Medicine and Biology, Kazan (Volga Region) Federal University, 420008 Kazan, Russia; (A.N.); (E.D.); (A.A.); (Y.S.); (O.I.)
| | - Elena Dudkina
- Department of Microbiology, Institute of Fundamental Medicine and Biology, Kazan (Volga Region) Federal University, 420008 Kazan, Russia; (A.N.); (E.D.); (A.A.); (Y.S.); (O.I.)
| | - Aleksandra Kuznetsova
- Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russia; (A.K.); (D.N.); (N.K.)
| | - Albina Ahmetgalieva
- Department of Microbiology, Institute of Fundamental Medicine and Biology, Kazan (Volga Region) Federal University, 420008 Kazan, Russia; (A.N.); (E.D.); (A.A.); (Y.S.); (O.I.)
| | - Dzhigangir Faizullin
- Kazan Institute of Biochemistry and Biophysics, FRC Kazan Scientific Center of RAS, 420111 Kazan, Russia; (D.F.); (Y.Z.)
| | - Yulia Surchenko
- Department of Microbiology, Institute of Fundamental Medicine and Biology, Kazan (Volga Region) Federal University, 420008 Kazan, Russia; (A.N.); (E.D.); (A.A.); (Y.S.); (O.I.)
| | - Darya Novopashina
- Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russia; (A.K.); (D.N.); (N.K.)
| | - Yuriy Zuev
- Kazan Institute of Biochemistry and Biophysics, FRC Kazan Scientific Center of RAS, 420111 Kazan, Russia; (D.F.); (Y.Z.)
| | - Nikita Kuznetsov
- Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russia; (A.K.); (D.N.); (N.K.)
| | - Olga Ilinskaya
- Department of Microbiology, Institute of Fundamental Medicine and Biology, Kazan (Volga Region) Federal University, 420008 Kazan, Russia; (A.N.); (E.D.); (A.A.); (Y.S.); (O.I.)
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3
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Chen K, Ojha SC, Imtong C, Linn AK, Li HC, Thonabulsombat C, Angsuthanasombat C. Molecular Insights into Zn 2+ Inhibition of the Antibacterial Endopeptidase Lysostaphin from Staphylococcus simulans. Protein Pept Lett 2021; 28:140-148. [PMID: 32533816 DOI: 10.2174/0929866527666200613221359] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Revised: 05/05/2020] [Accepted: 05/07/2020] [Indexed: 11/22/2022]
Abstract
BACKGROUND Mature lysostaphin (~28-kDa Lss) from Staphylococcus simulans proves effective in killing methicillin-resistant Staphylococcus aureus (MRSA) which is endemic in hospitals worldwide. Lss is Zn2+-dependent endopeptidase, but its bacteriolytic activity could be affected by exogenously added Zn2+. OBJECTIVE To gain greater insights into structural and functional impacts of Zn2+and Ni2+on Lss-induced bioactivity. METHODS Lss purified via immobilized metal ion-affinity chromatography was assessed for bioactivity using turbidity reduction assays. Conformational change of metal ion-treated Lss was examined by circular dichroism and intrinsic fluorescence spectroscopy. Co-sedimentation assay was performed to study interactions between Zn2+-treated Lss and S. aureus peptidoglycans. Metal ionbinding prediction and intermolecular docking were used to locate an extraneous Zn2+-binding site. RESULTS A drastic decrease in Lss bioactivity against S. aureus and MRSA was revealed only when treated with Zn2+, but not Ni2+, albeit no negative effect of diethyldithiocarbamate-Zn2+-chelator on Lss-induced bioactivity. No severe conformational change was observed for Lss incubated with exogenous Zn2+ or Ni2+. Lss pre-treated with Zn2+ efficiently bound to S. aureus cell-wall peptidoglycans, suggesting non-interfering effect of exogenous metal ions on cell-wall targeting (CWT) activity. In silico analysis revealed that exogenous Zn2+, but not Ni2+, preferably interacted with a potential extraneous Zn2+-binding site (His253, Glu318 and His323) placed near the Zn2+-coordinating Lssactive site within the catalytic (CAT) domain. CONCLUSION Our present data signify the adverse influence of exogenous Zn2+ ions on Lss-induced staphylolytic activity through the exclusive presence within the CAT domain of an extraneous inhibitory Zn2+-binding site, without affecting the CWT activity.
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Affiliation(s)
- Ke Chen
- Department of Anatomy, Faculty of Science, Mahidol University, Payatai Campus, Bangkok, Thailand
| | - Suvash Chandra Ojha
- Department of Infectious Diseases, The Affliliated Hospital of Southwest Medical University, Luzhou, China
| | - Chompounoot Imtong
- Division of Biology, Department of Science, Faculty of Science and Technology, Prince of Songkla University, Pattani Campus, Pattani, Thailand
| | - Aung Khine Linn
- Laboratory of Synthetic Biophysics and Chemical Biology, Biophysics Institute for Research and Development (BIRD), Chiang Mai, Thailand
| | - Hui-Chun Li
- Department of Biochemistry, School of Medicine, Tzu Chi University, Hualien, Taiwan
| | | | - Chanan Angsuthanasombat
- Laboratory of Synthetic Biophysics and Chemical Biology, Biophysics Institute for Research and Development (BIRD), Chiang Mai, Thailand
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4
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Wahiduzzaman, Dar MA, Haque MA, Idrees D, Hassan MI, Islam A, Ahmad F. Characterization of folding intermediates during urea-induced denaturation of human carbonic anhydrase II. Int J Biol Macromol 2017; 95:881-887. [DOI: 10.1016/j.ijbiomac.2016.10.073] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Revised: 10/07/2016] [Accepted: 10/22/2016] [Indexed: 11/25/2022]
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5
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Mahon BP, Bhatt A, Socorro L, Driscoll JM, Okoh C, Lomelino CL, Mboge MY, Kurian JJ, Tu C, Agbandje-McKenna M, Frost SC, McKenna R. The Structure of Carbonic Anhydrase IX Is Adapted for Low-pH Catalysis. Biochemistry 2016; 55:4642-53. [PMID: 27439028 DOI: 10.1021/acs.biochem.6b00243] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Human carbonic anhydrase IX (hCA IX) expression in many cancers is associated with hypoxic tumors and poor patient outcome. Inhibitors of hCA IX have been used as anticancer agents with some entering Phase I clinical trials. hCA IX is transmembrane protein whose catalytic domain faces the extracellular tumor milieu, which is typically associated with an acidic microenvironment. Here, we show that the catalytic domain of hCA IX (hCA IX-c) exhibits the necessary biochemical and biophysical properties that allow for low pH stability and activity. Furthermore, the unfolding process of hCA IX-c appears to be reversible, and its catalytic efficiency is thought to be correlated directly with its stability between pH 3.0 and 8.0 but not above pH 8.0. To rationalize this, we determined the X-ray crystal structure of hCA IX-c to 1.6 Å resolution. Insights from this study suggest an understanding of hCA IX-c stability and activity in low-pH tumor microenvironments and may be applicable to determining pH-related effects on enzymes.
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Affiliation(s)
- Brian P Mahon
- Department of Biochemistry and Molecular Biology, University of Florida College of Medicine , Gainesville, Florida 32610, United States
| | - Avni Bhatt
- Department of Biochemistry and Molecular Biology, University of Florida College of Medicine , Gainesville, Florida 32610, United States
| | - Lilien Socorro
- Department of Biochemistry and Molecular Biology, University of Florida College of Medicine , Gainesville, Florida 32610, United States
| | - Jenna M Driscoll
- Department of Biochemistry and Molecular Biology, University of Florida College of Medicine , Gainesville, Florida 32610, United States
| | - Cynthia Okoh
- Department of Biochemistry and Molecular Biology, University of Florida College of Medicine , Gainesville, Florida 32610, United States
| | - Carrie L Lomelino
- Department of Biochemistry and Molecular Biology, University of Florida College of Medicine , Gainesville, Florida 32610, United States
| | - Mam Y Mboge
- Department of Biochemistry and Molecular Biology, University of Florida College of Medicine , Gainesville, Florida 32610, United States
| | - Justin J Kurian
- Department of Biochemistry and Molecular Biology, University of Florida College of Medicine , Gainesville, Florida 32610, United States
| | - Chingkuang Tu
- Department of Biochemistry and Molecular Biology, University of Florida College of Medicine , Gainesville, Florida 32610, United States
| | - Mavis Agbandje-McKenna
- Department of Biochemistry and Molecular Biology, University of Florida College of Medicine , Gainesville, Florida 32610, United States
| | - Susan C Frost
- Department of Biochemistry and Molecular Biology, University of Florida College of Medicine , Gainesville, Florida 32610, United States
| | - Robert McKenna
- Department of Biochemistry and Molecular Biology, University of Florida College of Medicine , Gainesville, Florida 32610, United States
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6
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Enders JR, McLean JA. Chiral and structural analysis of biomolecules using mass spectrometry and ion mobility-mass spectrometry. Chirality 2010; 21 Suppl 1:E253-64. [PMID: 19927374 DOI: 10.1002/chir.20806] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
This report describes the strategies for gas-phase chiral and structural characterization of biomolecules using mass spectrometry (MS) and ion mobility-MS (IM-MS) techniques. Because both MS and IM-MS do not directly provide chiral selectivity, methodologies for adding a chiral selector are discussed in the context of (i) host-guest (H-G) associations, (ii) diastereomeric collision-induced dissociation (CID) methods, (iii) ion-molecule reactions, and (iv) the kinetic method. MS techniques for the analysis of proteins and protein complexes are briefly described. New advances in performing rapid 2D gas-phase separations on the basis of IM-MS are reviewed with a particular emphasis on the different forms of IM instrumentation and how they are used for chiral and/or structural biomolecular studies. This report is not intended to be a comprehensive review of the field, but rather to underscore the contemporary techniques that are commonly or increasingly being used to complement measurements performed by chiroptical methodologies.
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Affiliation(s)
- Jeffrey R Enders
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee, USA
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7
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Gudiksen KL, Urbach AR, Gitlin I, Yang J, Vazquez JA, Costello CE, Whitesides GM. Influence of the Zn(II) cofactor on the refolding of bovine carbonic anhydrase after denaturation with sodium dodecyl sulfate. Anal Chem 2005; 76:7151-61. [PMID: 15595855 DOI: 10.1021/ac0488560] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
This paper uses capillary electrophoresis to follow a globular metalloprotein--bovine carbonic anhydrase II (BCA, EC 4.2.1.1)--on unfolding upon treatment with sodium dodecyl sulfate (SDS) and refolding upon removal of SDS, both in the presence and the absence of its Zn(II) cofactor. This research demonstrates that the Zn(II) cofactor is not required for refolding into a nativelike conformation, does not remain associated with the unfolded protein, and does not significantly change the rate of refolding. The presence of the Zn(II) cofactor, however, does increase the total amount of recovered protein by a factor of 2. Capillary electrophoresis could distinguish between native and denatured protein, based on the difference in electrophoretic mobility between the native protein and the aggregate of denatured protein and SDS. In addition, the active site was probed by observing binding of BCA to a charged arylsulfonamide using affinity capillary electrophoresis. These studies provide a foundation for future physical-organic studies using BCA as a model to examine interactions between proteins and SDS.
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Affiliation(s)
- Katherine L Gudiksen
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA
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8
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Lundqvist M, Sethson I, Jonsson BH. Protein adsorption onto silica nanoparticles: conformational changes depend on the particles' curvature and the protein stability. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2004; 20:10639-47. [PMID: 15544396 DOI: 10.1021/la0484725] [Citation(s) in RCA: 326] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
We have analyzed the adsorption of protein to the surfaces of silica nanoparticles with diameters of 6, 9, and 15 nm. The effects upon adsorption on variants of human carbonic anhydrase with differing conformational stabilities have been monitored using methods that give complementary information, i.e., circular dichroism (CD), nuclear magnetic resonance (NMR), analytical ultracentrifugation (AUC), and gel permeation chromatography. Human carbonic anhydrase I (HCAI), which is the most stable of the protein variants, establishes a dynamic equilibrium between bound and unbound protein following mixture with silica particles. Gel permeation and AUC experiments indicate that the residence time of HCAI is on the order of approximately 10 min and slowly increases with time, which allows us to study the effects of the interaction with the solid surface on the protein structure in more detail than would be possible for a process with faster kinetics. The effects on the protein conformation from the interaction have been characterized using CD and NMR measurements. This study shows that differences in particle curvature strongly influence the amount of the protein's secondary structure that is perturbed. Particles with a longer diameter allow formation of larger particle-protein interaction surfaces and cause larger perturbations of the protein's secondary structure upon interaction. In contrast, the effects on the tertiary structure seem to be independent of the particles' curvature.
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Affiliation(s)
- Martin Lundqvist
- Molecular Biotechnology/IFM, Linköping University, SE-58183 Linköping, Sweden
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9
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Alam MT, Yamada T, Carlsson U, Ikai A. The importance of being knotted: effects of the C-terminal knot structure on enzymatic and mechanical properties of bovine carbonic anhydrase II. FEBS Lett 2002; 519:35-40. [PMID: 12023014 DOI: 10.1016/s0014-5793(02)02693-5] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In order to better understand the contribution of the knotted folding pattern to the enzymatic and mechanical properties of carbonic anhydrases, we replaced Gln-253 of bovine carbonic anhydrase II with Cys, which allowed us to measure the mechanical strength of the protein against tensile deformation by avoiding knot tightening. The expressed protein, to our surprise, turned out to contain two conformational isomers, one capable of binding an enzymatic inhibitor and the other not, which led to their separation through affinity chromatography. In near- and far-UV circular dichroism and fluorescence spectra, the separated conformers were very similar to each other and to the wild-type enzyme, indicating that they both had native-like conformations. We describe new evidence which supports the notion that the difference between the two conformers is likely to be related to the completeness of the C-terminal knot formation.
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Affiliation(s)
- Mohammad Taufiq Alam
- Laboratory of Biodynamics, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama, Japan
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10
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Andersson D, Carlsson U, Freskgård PO. Contribution of tryptophan residues to the CD spectrum of the extracellular domain of human tissue factor: application in folding studies and prediction of secondary structure. EUROPEAN JOURNAL OF BIOCHEMISTRY 2001; 268:1118-28. [PMID: 11179978 DOI: 10.1046/j.1432-1327.2001.01981.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The contribution to the circular dichroism (CD) spectrum made by each of the four Trp residues in the extracellular domain of human tissue factor, sTF (s designates soluble), was determined from difference CD spectra. The individual Trp CD spectra showed that all four residues contributed to the CD spectrum in almost the entire wavelength region investigated (180-305 nm). The sum of the individual spectra of each Trp residue in the near-UV region was qualitatively identical to the wild-type spectrum, clearly demonstrating that the Trp residues are the major contributors to the spectrum in this wavelength region. Trp CD bands interfere with the peptide bands in the far-UV region, leading to uncertainty in the predictions of the amounts of various types of secondary structure. Accordingly, the best prediction of secondary sTF structure content was achieved using a hypothetical Trp-free CD spectrum obtained after subtraction of all individual Trp spectra from the wild-type spectrum. The mutated Trp residues were also exploited as intrinsic probes to monitor the formation of local native-like tertiary structure by kinetic near-UV CD measurements. The global folding reaction was followed in parallel with a novel functional assay that registered the recovery of cofactor activity, i.e. stimulation of the amidolytic activity of Factor VIIa. From these measurements, it was found that sTF appears to regain FVIIa cofactor activity before the final side-chain packing of the Trp residues. The combined kinetic refolding results suggest that the compact asymmetric environments of the individual Trp residues in sTF are formed simultaneously, leading to the conclusion that the native tertiary structure of the whole protein is formed in a cooperative manner.
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Affiliation(s)
- D Andersson
- IFM-Department of Chemistry, Linköping University, Sweden
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11
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Borén K, Andersson P, Larsson M, Carlsson U. Characterization of a molten globule state of bovine carbonic anhydrase III: loss of asymmetrical environment of the aromatic residues has a profound effect on both the near- and far-UV CD spectrum. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1430:111-8. [PMID: 10082939 DOI: 10.1016/s0167-4838(98)00283-0] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Bovine muscle carbonic anhydrase (isoenzyme III; BCAIII) exhibited a three-state unfolding process at equilibrium upon denaturation in guanidine hydrochloride (GuHCl). The stable folding intermediate appeared to be of molten globule type. The stability towards GuHCl in terms of mid-point concentrations of denaturation were very similar for BCAIII and human CAII (HCAII). It was further demonstrated that the aromatic amino acid residues contributed significantly to the circular dichroism (CD) spectrum in the far-UV wavelength region during the native-->molten globule state transition. Thus, the ellipiticity change at 218 nm was shown to monitor the loss of tertiary interactions of aromatic side chains at the first unfolding transition as well as the rupture of secondary structure at the second unfolding transition. Similar aromatic contributions to the far-UV CD spectrum, but with varying magnitudes, were also noted for BCAII and HCAII, further emphasizing that interference of aromatic residues should not be neglected at wavelengths that normally are assigned to secondary structural changes.
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Affiliation(s)
- K Borén
- IFM/Department of Chemistry, Linköping University, SE-581 83, Linköping, Sweden
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12
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Abstract
The folding mechanism of cellular retinoic acid binding protein I (CRABP I), cellular retinol binding protein II (CRBP II), and intestinal fatty acid binding protein (IFABP) were investigated to determine if proteins with similar native structures have similar folding mechanisms. These mostly beta-sheet proteins have very similar structures, despite having as little as 33% sequence similarity. The reversible urea denaturation of these proteins was characterized at equilibrium by circular dichroism and fluorescence. The data were best fit by a two-state model for each of these proteins, suggesting that no significant population of folding intermediates were present at equilibrium. The native states were of similar stability with free energies (linearly extrapolated to 0 M urea, deltaGH2O) of 6.5, 8.3, and 5.5 kcal/mole for CRABP I, CRBP II, and IFABP, respectively. The kinetics of the folding and unfolding processes for these proteins was monitored by stopped-flow CD and fluorescence. Intermediates were observed during both the folding and unfolding of all of these proteins. However, the overall rates of folding and unfolding differed by nearly three orders of magnitude. Further, the spectroscopic properties of the intermediate states were different for each protein, suggesting that different amounts of secondary and/or tertiary structure were associated with each intermediate state for each protein. These data show that the folding path for proteins in the same structural family can be quite different, and provide evidence for different folding landscapes for these sequences.
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Affiliation(s)
- L L Burns
- Department of Biochemistry and Molecular Biology, Pennsylvania State University, College of Medicine, Hershey 17033, USA
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13
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Krittanai C, Johnson WC. Correcting the circular dichroism spectra of peptides for contributions of absorbing side chains. Anal Biochem 1997; 253:57-64. [PMID: 9356142 DOI: 10.1006/abio.1997.2366] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The aromatic and sulfur-containing side chains Trp, Tyr, Phe, Cys, and Met contribute to the CD spectra of peptides and proteins in the amide region, interfering with the analysis for secondary structure. We propose a method to correct the CD spectra of peptides undergoing the helix-coil transition for contributions due to absorbing side chains using singular value decomposition. The method uses the common basis vectors obtained from an analysis of the CD spectra of related peptides without the aromatic and sulfur-containing amino acids. The common basis vectors are fitted to a portion of the CD spectrum of the peptide being corrected, in the range that is unaffected by its sidechain contributions. Then the resulting coefficients from the fitting are used along with the common basis vectors to regenerate the entire corrected spectrum. The method is illustrated for the CD spectra of the peptide sequence acetyl-Y-VAXAK-VAXAK-VAXAK-amide, where X is substituted with the 20 naturally occurring amino acids. This peptide model adopts a random-coil conformation in 2 mm sodium phosphate buffer, pH 5.5, and becomes an alpha helix in methanol/buffer solutions. The difference between the original and corrected spectra shows the contribution from the aromatic and sulfur-containing side chains.
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Affiliation(s)
- C Krittanai
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331-7305, USA
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14
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Lima LM, de Prat-Gay G. Conformational changes and stabilization induced by ligand binding in the DNA-binding domain of the E2 protein from human papillomavirus. J Biol Chem 1997; 272:19295-303. [PMID: 9235925 DOI: 10.1074/jbc.272.31.19295] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
We are investigating the folding of the 81-residue recombinant dimeric DNA binding domain of the E2 protein from human papillomavirus and how it is coupled to the binding of its DNA ligand. Modifications in buffer composition, such as ionic strength and phosphate, cause an approximately 5.0 kcal mol-1 stabilization of the domain to urea unfolding, based on very similar conformational changes as measured by far UV circular dichroism. Binding of DNA produces an even greater stabilization, magnitude similar to that caused by the nonspecific polymer ligand heparin, which shifts the urea midpoint 2.5-fold. The DNA-bound complex displays substantial changes similar to those caused by ionic strength and phosphate in terms of overall secondary structure. Bis-8-anilino-1-naphthalenesulfonate provides a very sensitive conformational probe, which shows alterations in the domain caused by the above mentioned compounds. In general terms, binding of DNA involves an overall conformational readjustment in the protein but maintains the beta-barrel scaffold intact. This conformational plasticity seems to be of importance in the regulatory functions of this type of DNA-binding protein. The extremely long half-life of the E2-DNA complex, together with its very high stability, suggests that, in the absence of other factors that may affect its stability in vivo, the possibility of dissociation once formed is restricted.
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Affiliation(s)
- L M Lima
- Departamento de Bioquímica Médica-ICB, Universidade Federal do Rio de Janeiro, Cidade Universitaria, Rio de Janeiro 21941-590, Brazil
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