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Zeynaloo E, Zahran EM, Yang YP, Dikici E, Head T, Bachas LG, Daunert S. Reagentless electrochemical biosensors through incorporation of unnatural amino acids on the protein structure. Biosens Bioelectron 2022; 200:113861. [PMID: 34986438 PMCID: PMC9404255 DOI: 10.1016/j.bios.2021.113861] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Revised: 11/19/2021] [Accepted: 12/01/2021] [Indexed: 11/19/2022]
Abstract
Typical protein biosensors employ chemical or genetic labeling of the protein, thus introducing an extraneous molecule to the wild-type parent protein, often changing the overall structure and properties of the protein. While these labeling methods have proven successful in many cases, they also have a series of disadvantages associated with their preparation and function. An alternative route for labeling proteins is the incorporation of unnatural amino acid (UAA) analogues, capable of acting as a label, into the structure of a protein. Such an approach, while changing the local microenvironment, poses less of a burden on the overall structure of the protein. L-DOPA is an analog of phenylalanine and contains a catechol moiety that participates in a quasi-reversible, two-electron redox process, thus making it suitable as an electrochemical label/reporter. The periplasmic glucose/galactose binding protein (GBP) was chosen to demonstrate this detection principle. Upon glucose binding, GBP undergoes a significant conformational change that is manifested as a change in the electrochemistry of L-DOPA. The electroactive GBP was immobilized onto gold nanoparticle-modified, polymerized caffeic acid, screen-printed carbon electrodes (GBP-LDOPA/AuNP/PCA/SPCE) for the purpose of direct measurement of glucose levels and serves as a proof-of-concept of the use of electrochemically-active unnatural amino acids as the label. The resulting reagentless GBP biosensors exhibited a highly selective and sensitive binding affinity for glucose in the micromolar range, laying the foundation for a new biosensing methodology based on global incorporation of an electroactive amino acid into the protein's primary sequence for highly selective electrochemical detection of compounds of interest.
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Affiliation(s)
- Elnaz Zeynaloo
- Department of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL, 33136, United States; Department of Chemistry, University of Miami, Miami, FL, 33134, United States
| | - Elsayed M Zahran
- Department of Chemistry, Ball State University, Muncie, IN, 47306, United States
| | - Yu-Ping Yang
- Department of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL, 33136, United States; Dr. JT Macdonald Foundation Biomedical Nanotechnology Institute, University of Miami, Miami, FL, 33136, United States
| | - Emre Dikici
- Department of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL, 33136, United States; Dr. JT Macdonald Foundation Biomedical Nanotechnology Institute, University of Miami, Miami, FL, 33136, United States; Clinical and Translational Science Institute, University of Miami, Miami, FL, 33136, United States
| | - Trajen Head
- Department of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL, 33136, United States; Dr. JT Macdonald Foundation Biomedical Nanotechnology Institute, University of Miami, Miami, FL, 33136, United States
| | - Leonidas G Bachas
- Department of Chemistry, University of Miami, Miami, FL, 33134, United States; Dr. JT Macdonald Foundation Biomedical Nanotechnology Institute, University of Miami, Miami, FL, 33136, United States
| | - Sylvia Daunert
- Department of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL, 33136, United States; Dr. JT Macdonald Foundation Biomedical Nanotechnology Institute, University of Miami, Miami, FL, 33136, United States; Clinical and Translational Science Institute, University of Miami, Miami, FL, 33136, United States.
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Pushina M, Penavic A, Farshbaf S, Anzenbacher P. Fluorescent Sensor Array for Quantitative Determination of Saccharides. ACS Sens 2021; 6:4001-4008. [PMID: 34669369 DOI: 10.1021/acssensors.1c01371] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Accurate monitoring of sugar levels is essential for many fields from food industry to human health. Here, we developed FRET-based dual chromophore sensors for saccharides that form oxazolidine boronate and may be employed as a noninvasive method for monitoring of sugar levels in biological fluids, namely, urine. The saccharide-binding properties of the sensors were studied using fluorescence spectroscopy and utilized in the determination of saccharides in a high-throughput manner. Here, two fluorescent sensors were successful in the classification of nine different monosaccharides and disaccharides with 100% correct classification. Furthermore, the dual chromophore self-assembled sensors were successfully utilized for the quantitative determination of important carbohydrates such as glucose in the presence of competitive saccharides (fructose) and in complex media (urine) without sample pretreatment. The present fluorescent sensors allow for quantification of glucose in a concentration range of 0-60 mM, which matches the concentration range of frequently used urinalysis test strips.
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Affiliation(s)
- Mariia Pushina
- Department of Chemistry, Bowling Green State University, Bowling Green, Ohio 43403, United States
| | - Andrej Penavic
- Department of Chemistry, Bowling Green State University, Bowling Green, Ohio 43403, United States
| | - Sepideh Farshbaf
- Department of Chemistry, Bowling Green State University, Bowling Green, Ohio 43403, United States
| | - Pavel Anzenbacher
- Department of Chemistry, Bowling Green State University, Bowling Green, Ohio 43403, United States
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Bioinformatics analysis and biochemical characterisation of ABC transporter-associated periplasmic substrate-binding proteins ModA and MetQ from Helicobacter pylori strain SS1. Biophys Chem 2021; 272:106577. [PMID: 33756269 DOI: 10.1016/j.bpc.2021.106577] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2021] [Revised: 02/23/2021] [Accepted: 03/06/2021] [Indexed: 12/29/2022]
Abstract
The human gastric pathogen Helicobacter pylori relies on the uptake of host-provided nutrients for its proliferation and pathogenicity. ABC transporters that mediate import of small molecules into the cytoplasm of H. pylori employ their cognate periplasmic substrate-binding proteins (SBPs) for ligand capture in the periplasm. The genome of the mouse-adapted strain SS1 of H. pylori encodes eight ABC transporter-associated SBPs, but little is known about their specificity or structure. In this study, we demonstrated that the SBP annotated as ModA binds molybdate (MoO42-, KD = 3.8 nM) and tungstate (WO42-, KD = 7.8 nM). In addition, we showed that MetQ binds D-methionine (KD = 9.5 μM), but not L-methionine, which suggests the existence of as yet unknown pathway for L-methionine uptake. Homology modelling has led to identification of the ligand-binding residues.
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