1
|
Kluz M, Nieznańska H, Dec R, Dzięcielewski I, Niżyński B, Ścibisz G, Puławski W, Staszczak G, Klein E, Smalc-Koziorowska J, Dzwolak W. Revisiting the conformational state of albumin conjugated to gold nanoclusters: A self-assembly pathway to giant superstructures unraveled. PLoS One 2019; 14:e0218975. [PMID: 31247048 PMCID: PMC6597083 DOI: 10.1371/journal.pone.0218975] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Accepted: 06/12/2019] [Indexed: 11/21/2022] Open
Abstract
Bovine serum albumin (BSA) is often employed as a proteinaceous component for synthesis of luminescent protein-stabilized gold nanoclusters (AuNC): intriguing systems with many potential applications. Typically, the formation of BSA-AuNC conjugate occurs under strongly alkaline conditions. Due to the sheer complexity of intertwined chemical and structural transitions taking place upon BSA-AuNC formation, the state of albumin enveloping AuNCs remains poorly characterized. Here, we study the conformational properties of BSA bound to AuNCs using an array of biophysical tools including vibrational spectroscopy, circular dichroism, fluorescence spectroscopy and trypsin digestion. The alkaline conditions of BSA-AuNC self-assembly appear to be primary responsible for the profound irreversible disruption of tertiary contacts, partial unfolding of native α-helices, hydrolysis of disulfide bonds and the protein becoming vulnerable to trypsin digestion. Further unfolding of BSA-AuNC by guanidinium hydrochloride (GdnHCl) is fully reversible equally in terms of albumin's secondary structure and conjugate's luminescent properties. This suggests that binding to AuNCs traps the albumin molecule in a state that is both partly disordered and refractory to irreversible misfolding. Indeed, when BSA-AuNC is subjected to conditions favoring self-association of BSA into amyloid-like fibrils, the buildup of non-native β-sheet conformation is less pronounced than in a control experiment with unmodified BSA. Unexpectedly, BSA-AuNC reveals a tendency to self-assemble into giant twisted superstructures of micrometer lengths detectable with transmission electron microscopy (TEM), a property absent in unmodified BSA. The process is accompanied by ordering of bound AuNCs into elongated streaks and simultaneous decrease in fluorescence intensity. The newly discovered self-association pathway appears to be specifically accessible to protein molecules with a certain restriction on structural dynamics which in the case of BSA-AuNC arises from binding to metal nanoclusters. Our results have been discussed in the context of mechanisms of protein misfolding and applications of BSA-AuNC.
Collapse
MESH Headings
- Amino Acid Sequence
- Animals
- Cattle
- Circular Dichroism
- Gold/chemistry
- Metal Nanoparticles/chemistry
- Metal Nanoparticles/ultrastructure
- Microscopy, Atomic Force
- Microscopy, Electron, Scanning
- Microscopy, Electron, Transmission
- Models, Molecular
- Protein Aggregates
- Protein Conformation
- Protein Denaturation
- Protein Stability
- Serum Albumin, Bovine/chemistry
- Serum Albumin, Bovine/genetics
- Serum Albumin, Bovine/ultrastructure
- Spectrometry, Fluorescence
- Spectroscopy, Fourier Transform Infrared
- Spectrum Analysis, Raman
Collapse
Affiliation(s)
- Michał Kluz
- Institute of High Pressure Physics, Polish Academy of Sciences, Warsaw, Poland
| | - Hanna Nieznańska
- Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland
| | - Robert Dec
- Institute of High Pressure Physics, Polish Academy of Sciences, Warsaw, Poland
- Department of Chemistry, Biological and Chemical Research Centre, University of Warsaw, Warsaw, Poland
| | - Igor Dzięcielewski
- Institute of High Pressure Physics, Polish Academy of Sciences, Warsaw, Poland
| | - Bartosz Niżyński
- Department of Chemistry, Biological and Chemical Research Centre, University of Warsaw, Warsaw, Poland
| | - Grzegorz Ścibisz
- Department of Chemistry, Biological and Chemical Research Centre, University of Warsaw, Warsaw, Poland
| | - Wojciech Puławski
- Institute of High Pressure Physics, Polish Academy of Sciences, Warsaw, Poland
| | - Grzegorz Staszczak
- Institute of High Pressure Physics, Polish Academy of Sciences, Warsaw, Poland
| | - Ewelina Klein
- Institute of High Pressure Physics, Polish Academy of Sciences, Warsaw, Poland
| | | | - Wojciech Dzwolak
- Institute of High Pressure Physics, Polish Academy of Sciences, Warsaw, Poland
- Department of Chemistry, Biological and Chemical Research Centre, University of Warsaw, Warsaw, Poland
| |
Collapse
|
2
|
Affiliation(s)
- Anna Szakiel
- a Department of Plant Biochemistry, Faculty of Biology , University of Warsaw , ul. Miecznikowa 1, 02-096 , Warszawa , Poland
| | - Bartosz Niżyński
- a Department of Plant Biochemistry, Faculty of Biology , University of Warsaw , ul. Miecznikowa 1, 02-096 , Warszawa , Poland
| | - Cezary Pączkowski
- a Department of Plant Biochemistry, Faculty of Biology , University of Warsaw , ul. Miecznikowa 1, 02-096 , Warszawa , Poland
| |
Collapse
|