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van der Ven AM, Gyamfi H, Suttisansanee U, Ahmad MS, Su Z, Taylor RM, Poole A, Chiorean S, Daub E, Urquhart T, Honek JF. Molecular Engineering of E. coli Bacterioferritin: A Versatile Nanodimensional Protein Cage. Molecules 2023; 28:4663. [PMID: 37375226 DOI: 10.3390/molecules28124663] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Revised: 05/23/2023] [Accepted: 06/05/2023] [Indexed: 06/29/2023] Open
Abstract
Currently, intense interest is focused on the discovery and application of new multisubunit cage proteins and spherical virus capsids to the fields of bionanotechnology, drug delivery, and diagnostic imaging as their internal cavities can serve as hosts for fluorophores or bioactive molecular cargo. Bacterioferritin is unusual in the ferritin protein superfamily of iron-storage cage proteins in that it contains twelve heme cofactors and is homomeric. The goal of the present study is to expand the capabilities of ferritins by developing new approaches to molecular cargo encapsulation employing bacterioferritin. Two strategies were explored to control the encapsulation of a diverse range of molecular guests compared to random entrapment, a predominant strategy employed in this area. The first was the inclusion of histidine-tag peptide fusion sequences within the internal cavity of bacterioferritin. This approach allowed for the successful and controlled encapsulation of a fluorescent dye, a protein (fluorescently labeled streptavidin), or a 5 nm gold nanoparticle. The second strategy, termed the heme-dependent cassette strategy, involved the substitution of the native heme with heme analogs attached to (i) fluorescent dyes or (ii) nickel-nitrilotriacetate (NTA) groups (which allowed for controllable encapsulation of a histidine-tagged green fluorescent protein). An in silico docking approach identified several small molecules able to replace the heme and capable of controlling the quaternary structure of the protein. A transglutaminase-based chemoenzymatic approach to surface modification of this cage protein was also accomplished, allowing for future nanoparticle targeting. This research presents novel strategies to control a diverse set of molecular encapsulations and adds a further level of sophistication to internal protein cavity engineering.
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Affiliation(s)
- Anton M van der Ven
- Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Hawa Gyamfi
- Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | | | - Muhammad S Ahmad
- Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Zhengding Su
- Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Robert M Taylor
- Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Amanda Poole
- Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Sorina Chiorean
- Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Elisabeth Daub
- Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Taylor Urquhart
- Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - John F Honek
- Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada
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Castillo O, Mancillas J, Hughes W, Brancaleon L. Characterization of the interaction of metal-protoporphyrins photosensitizers with β- lactoglobulin. Biophys Chem 2023; 292:106918. [PMID: 36399946 DOI: 10.1016/j.bpc.2022.106918] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Revised: 10/24/2022] [Accepted: 10/27/2022] [Indexed: 11/17/2022]
Abstract
We investigated the interaction of a series of metal-protoporphyrins (PPIXs) with bovine β- lactoglobulin (BLG) using a combination of optical spectroscopy and computational simulations. Unlike other studies, the simulations were not merely used to rationalize the experimental data but were employed to refine the experimental data itself. The study was carried out at two pH values, 5 and 9, where BLG is known to have different conformation dictated by the so-called Tanford transition which occurs near pH 7.5. The transition is postulated to regulate access to the interior binding cavity of the protein, thus the pH variation was used as a parameter to investigate whether PPIXs access the central cavity of BLG. The results of our study show that indeed binding increases significantly at alkaline pH, however, the increased affinity is not due to the accessibility of the central cavity. Instead, binding appears to be determined by the tendency of PPIXs to form large inhomogeneous aggregates at acidic pH which hinders interactions with proteins. The binding site determined through a combination of experimental and computational methods is located at the interface between two BLG monomers where the long α-helix segment of the protein face each other. This region is rich in positively charged Lys residues that interact with the propionic acid chains of the protoporphyrins. Establishing the modality of binding between protoporphyrins and BLG would have important consequences for the use of BLG:PPIX complexes in applications such as artificial photoreceptors, artificial metallo-enzymes, delivery of photosensitizers for phototherapy and even solar energy conversion.
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Affiliation(s)
- Omar Castillo
- Department of Physics and Astronomy, University of Texas at San Antonio, San Antonio, TX 78249, USA
| | - James Mancillas
- Department of Physics and Astronomy, University of Texas at San Antonio, San Antonio, TX 78249, USA
| | - William Hughes
- Department of Physics and Astronomy, University of Texas at San Antonio, San Antonio, TX 78249, USA
| | - Lorenzo Brancaleon
- Department of Physics and Astronomy, University of Texas at San Antonio, San Antonio, TX 78249, USA.
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Sakae H. Spectroscopic Analysis of Apoferritin Associates with the Water-Soluble Porphyrins. Photochem Photobiol 2021; 97:930-935. [PMID: 34161607 DOI: 10.1111/php.13476] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2021] [Accepted: 06/21/2021] [Indexed: 11/27/2022]
Abstract
The association behavior of apoferritin species with the anionic porphyrins, 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (H2 TPPS4- ) and its zinc(II) complex (ZnTPPS4- ), which are water-soluble even in acidic solutions, was investigated for the first time through UV-Vis absorption and fluorescence spectroscopy in order to evaluate a potential ability of apoferritin as a stimuli-responsive molecular capsule. The absorption maximum wavelengths of both porphyrins were redshifted and the fluorescence intensity decreased, indicating the effective association between apoferritin species and the porphyrins, although it depended on the pH adjustment procedure. At pH 2, the ZnTPPS4- associated with apoferritin subunits without demetallating and protonating, while the free base porphyrin formed the J-aggregate of the diprotonated species (H4 TPPS2- )n , with extremely low fluorescence. As the concentration of apoferritin subunits increased, the H2 TPPS4- -subunits associates were formed accompanied by recovering the fluorescence. The association stoichiometries of 1 or 2 subunits/porphyrin obtained under neutral and acidic conditions. The significantly large association constant of ZnTPPS4- as compared with that of H2 TPPS4- indicated that the coordination to the zinc(II) center strongly contributes to the association in addition to the electrostatic interaction between apoferritin subunits and the porphyrin under acidic conditions.
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Affiliation(s)
- Hiroki Sakae
- Department of Bioscience and Biotechnology, Fukui Prefectural University, Eiheiji, Japan
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Benavides BS, Valandro S, Cioloboc D, Taylor AB, Schanze KS, Kurtz DM. Structure of a Zinc Porphyrin-Substituted Bacterioferritin and Photophysical Properties of Iron Reduction. Biochemistry 2020; 59:1618-1629. [PMID: 32283930 PMCID: PMC7927158 DOI: 10.1021/acs.biochem.9b01103] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The iron storage protein bacterioferritin (Bfr) binds up to 12 hemes b at specific sites in its protein shell. The heme b can be substituted with the photosensitizer Zn(II)-protoporphyrin IX (ZnPP), and photosensitized reductive iron release from the ferric oxyhydroxide {[FeO(OH)]n} core inside the ZnPP-Bfr protein shell was demonstrated [Cioloboc, D., et al. (2018) Biomacromolecules 19, 178-187]. This report describes the X-ray crystal structure of ZnPP-Bfr and the effects of loaded iron on the photophysical properties of the ZnPP. The crystal structure of ZnPP-Bfr shows a unique six-coordinate zinc in the ZnPP with two axial methionine sulfur ligands. Steady state and transient ultraviolet-visible absorption and luminescence spectroscopies show that irradiation with light overlapping the Soret absorption causes oxidation of ZnPP to the cation radical ZnPP•+ only when the ZnPP-Bfr is loaded with [FeO(OH)]n. Femtosecond transient absorption spectroscopy shows that this photooxidation occurs from the singlet excited state (1ZnPP*) on the picosecond time scale and is consistent with two oxidizing populations of Fe3+, which do not appear to involve the ferroxidase center iron. We propose that [FeO(OH)]n clusters at or near the inner surface of the protein shell are responsible for ZnPP photooxidation. Hopping of the photoinjected electrons through the [FeO(OH)]n would effectively cause migration of Fe2+ through the inner cavity to pores where it exits the protein. Reductive iron mobilization is presumed to be a physiological function of Bfrs. The phototriggered Fe3+ reduction could be used to identify the sites of iron mobilization within the Bfr protein shell.
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Affiliation(s)
- Brenda S Benavides
- Department of Chemistry, University of Texas at San Antonio, San Antonio, Texas 78249, United States
| | - Silvano Valandro
- Department of Chemistry, University of Texas at San Antonio, San Antonio, Texas 78249, United States
| | - Daniela Cioloboc
- Department of Chemistry, University of Texas at San Antonio, San Antonio, Texas 78249, United States
| | - Alexander B Taylor
- Department of Biochemistry and Structural Biology and X-ray Crystallography Core Laboratory, University of Texas Health Science Center at San Antonio (UT Health San Antonio), San Antonio, Texas 78229, United States
| | - Kirk S Schanze
- Department of Chemistry, University of Texas at San Antonio, San Antonio, Texas 78249, United States
| | - Donald M Kurtz
- Department of Chemistry, University of Texas at San Antonio, San Antonio, Texas 78249, United States
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