1
|
Kane BJ, Okuda‐Shimazaki J, Andrews MM, Kerrigan JA, Murphy KV, Sode K. Discovery of periplasmic solute binding proteins with specificity for ketone bodies: β-hydroxybutyrate binding proteins. Protein Sci 2024; 33:e5025. [PMID: 38864689 PMCID: PMC11167705 DOI: 10.1002/pro.5025] [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: 02/03/2024] [Revised: 04/24/2024] [Accepted: 05/03/2024] [Indexed: 06/13/2024]
Abstract
Polyhydroxyalkanoates are a class of biodegradable, thermoplastic polymers which represent a major carbon source for various bacteria. Proteins which mediate the translocation of polyhydroxyalkanoate breakdown products, such as β-hydroxybutyrate (BHB)-a ketone body which in humans serves as an important biomarker, have not been well characterized. In our investigation to screen a solute-binding protein (SBP) which can act as a suitable recognition element for BHB, we uncovered insights at the intersection of bacterial metabolism and diagnostics. Herein, we identify SBPs associated with putative ATP-binding cassette transporters that specifically recognize BHB, with the potential to serve as recognition elements for continuous quantification of this analyte. Through bioinformatic analysis, we identified candidate SBPs from known metabolizers of polyhydroxybutyrate-including proteins from Cupriavidus necator, Ensifer meliloti, Paucimonas lemoignei, and Thermus thermophilus. After recombinant expression in Escherichia coli, we demonstrated with intrinsic tryptophan fluorescence spectroscopy that four candidate proteins interacted with BHB, ranging from nanomolar to micromolar affinity. Tt.2, an intrinsically thermostable protein from Thermus thermophilus, was observed to have the tightest binding and specificity for BHB, which was confirmed by isothermal calorimetry. Structural analyses facilitated by AlphaFold2, along with molecular docking and dynamics simulations, were used to hypothesize key residues in the binding pocket and to model the conformational dynamics of substrate unbinding. Overall, this study provides strong evidence identifying the cognate ligands of SBPs which we hypothesize to be involved in prokaryotic cellular translocation of polyhydroxyalkanoate breakdown products, while highlighting these proteins' promising biotechnological application.
Collapse
Affiliation(s)
- Bryant J. Kane
- Joint Department of Biomedical EngineeringThe University of North Carolina at Chapel Hill and North Carolina State UniversityChapel HillNorth CarolinaUSA
| | - Junko Okuda‐Shimazaki
- Department of Biotechnology and Life Science, Graduate School of EngineeringTokyo University of Agriculture and TechnologyTokyoJapan
| | - Madelyn M. Andrews
- Joint Department of Biomedical EngineeringThe University of North Carolina at Chapel Hill and North Carolina State UniversityChapel HillNorth CarolinaUSA
| | - Joseph A. Kerrigan
- Joint Department of Biomedical EngineeringThe University of North Carolina at Chapel Hill and North Carolina State UniversityChapel HillNorth CarolinaUSA
| | - Kyle V. Murphy
- Joint Department of Biomedical EngineeringThe University of North Carolina at Chapel Hill and North Carolina State UniversityChapel HillNorth CarolinaUSA
| | - Koji Sode
- Joint Department of Biomedical EngineeringThe University of North Carolina at Chapel Hill and North Carolina State UniversityChapel HillNorth CarolinaUSA
| |
Collapse
|
2
|
Allert MJ, Kumar S, Wang Y, Beese LS, Hellinga HW. Chromophore carbonyl twisting in fluorescent biosensors encodes direct readout of protein conformations with multicolor switching. Commun Chem 2023; 6:168. [PMID: 37598249 PMCID: PMC10439942 DOI: 10.1038/s42004-023-00982-7] [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: 05/31/2023] [Accepted: 08/11/2023] [Indexed: 08/21/2023] Open
Abstract
Fluorescent labeling of proteins is a powerful tool for probing structure-function relationships with many biosensing applications. Structure-based rules for systematically designing fluorescent biosensors require understanding ligand-mediated fluorescent response mechanisms which can be challenging to establish. We installed thiol-reactive derivatives of the naphthalene-based fluorophore Prodan into bacterial periplasmic glucose-binding proteins. Glucose binding elicited paired color exchanges in the excited and ground states of these conjugates. X-ray structures and mutagenesis studies established that glucose-mediated color switching arises from steric interactions that couple protein conformational changes to twisting of the Prodan carbonyl relative to its naphthalene plane. Mutations of residues contacting the carbonyl can optimize color switching by altering fluorophore conformational equilibria in the apo and glucose-bound proteins. A commonly accepted view is that Prodan derivatives report on protein conformations via solvatochromic effects due to changes in the dielectric of their local environment. Here we show that instead Prodan carbonyl twisting controls color switching. These insights enable structure-based biosensor design by coupling ligand-mediated protein conformational changes to internal chromophore twists through specific steric interactions between fluorophore and protein.
Collapse
Affiliation(s)
- Malin J Allert
- Department of Biochemistry, Duke University Medical Center, Durham, NC, 27710, USA
| | - Shivesh Kumar
- Department of Biochemistry, Duke University Medical Center, Durham, NC, 27710, USA
- Department of Biochemistry and Molecular Biophysics, Washington University in St. Louis, St. Louis, MO, 63110, USA
| | - You Wang
- Department of Biochemistry, Duke University Medical Center, Durham, NC, 27710, USA
| | - Lorena S Beese
- Department of Biochemistry, Duke University Medical Center, Durham, NC, 27710, USA
| | - Homme W Hellinga
- Department of Biochemistry, Duke University Medical Center, Durham, NC, 27710, USA.
| |
Collapse
|
3
|
Allert MJ, Hellinga HW. Discovery of Thermostable, Fluorescently Responsive Glucose Biosensors by Structure-Assisted Function Extrapolation. Biochemistry 2022; 61:276-293. [PMID: 35084821 DOI: 10.1021/acs.biochem.1c00738] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Accurate assignment of protein function from sequence remains a fascinating and difficult challenge. The periplasmic-binding protein (PBP) superfamily present an interesting case of function prediction because they are both ubiquitous in prokaryotes and tend to diversify through gene duplication "explosions" that can lead to large numbers of paralogs in a genome. An engineered version of the moderately thermostable glucose-binding PBP from Escherichia coli has been used successfully as a reagentless fluorescent biosensor both in vitro and in vivo. To develop more robust sensors that meet the challenges of real-world applications, we report the discovery of thermostable homologues that retain a glucose-mediated conformationally coupled fluorescence response. Accurately identifying a glucose-binding PBP homologue among closely related paralogs is challenging. We demonstrate that a structure-based method that filters sequences by residues that bind glucose in an archetype structure is highly effective. Using fully sequenced bacterial genomes, we found that this filter reduced high paralog numbers to single hits in a genome, consistent with the accurate separation of glucose binding from other functions. We expressed engineered proteins for eight homologues, chosen to represent different degrees of sequence identity, and tested their glucose-mediated fluorescence responses. We accurately predicted the presence of glucose binding down to 31% sequence identity. We have also successfully identified suitable candidates for next-generation robust, fluorescent glucose sensors.
Collapse
Affiliation(s)
- Malin J Allert
- Department of Biochemistry, Duke University Medical Center, Box 3711, Durham, North Carolina 27710, United States
| | - Homme W Hellinga
- Department of Biochemistry, Duke University Medical Center, Box 3711, Durham, North Carolina 27710, United States
| |
Collapse
|
4
|
Periplasmic-binding protein-based biosensors and bioanalytical assay platforms: Advances, considerations, and strategies for optimal utility. TALANTA OPEN 2021. [DOI: 10.1016/j.talo.2021.100038] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
|
5
|
Lee I, Probst D, Klonoff D, Sode K. Continuous glucose monitoring systems - Current status and future perspectives of the flagship technologies in biosensor research -. Biosens Bioelectron 2021; 181:113054. [DOI: 10.1016/j.bios.2021.113054] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Revised: 01/23/2021] [Accepted: 01/27/2021] [Indexed: 12/14/2022]
|
6
|
Allert MJ, Hellinga HW. Harnessing Environmental Ca 2+ for Extracellular Protein Thermostabilization. Biochemistry 2020; 59:3725-3740. [PMID: 32915552 DOI: 10.1021/acs.biochem.0c00449] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Ca2+ is the third-most prevalent metal ion in the environment. EF hands are common Ca2+-binding motifs found in both extracellular and intracellular proteins of eukaryotes and prokaryotes. Cytoplasmic EF hand proteins often mediate allosteric control of signal transduction pathway components in response to intracellular Ca2+ concentration fluctuations by coupling Ca2+ binding to changes in protein structure. We show that an extracellular structural Ca2+-binding site mediates protein thermostabilization by such conformational coupling as well. Binding Ca2+ to the EF hand of the extracellular (periplasmic) Escherichia coli glucose-galactose binding protein thermostabilizes this protein by ∼17 K relative to its Ca2+-free form. Using statistical thermodynamic analysis of a fluorescent conjugate of ecGGBP that reports simultaneously on ligand binding and multiple conformational states, we found that its Ca2+-mediated stabilization is determined by conformational coupling mechanisms in two independent conformational exchange reactions. Binding to folded and unfolded states determines the maximum Ca2+-mediated stability. A disorder → order transition accompanies the formation of the Ca2+ complex in the folded state and dictates the minimum Ca2+ concentration at which the Ca2+-bound state becomes dominant. Similar transitions also encode the structural changes necessary for Ca2+-mediated control elements in signal transduction pathways. Ca2+-mediated thermostabilization and allosteric control, therefore, share a fundamental conformational coupling mechanism, which may have implications for the evolution of EF hands.
Collapse
Affiliation(s)
- Malin J Allert
- Department of Biochemistry, Duke University Medical Center, P.O. Box 3711, Durham, North Carolina 27710, United States
| | - Homme W Hellinga
- Department of Biochemistry, Duke University Medical Center, P.O. Box 3711, Durham, North Carolina 27710, United States
| |
Collapse
|
7
|
Allert MJ, Hellinga HW. Describing Complex Structure-Function Relationships in Biomolecules at Equilibrium. J Mol Biol 2020; 432:1926-1951. [PMID: 31940471 DOI: 10.1016/j.jmb.2019.12.039] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Revised: 12/03/2019] [Accepted: 12/17/2019] [Indexed: 11/17/2022]
Abstract
One of the great ambitions of structural biology is to describe structure-function relationships quantitatively. Statistical thermodynamics is a powerful, general tool for computing the behavior of biological macromolecules at equilibrium because it establishes a direct link between structure and function. Complex behavior emerges as equilibria of multiple reactions are coupled. Analytical treatment of linked equilibria scales poorly with increasing numbers of reactions and states as the algebraic constructs rapidly become unwieldy. We therefore developed a generalizable, but straightforward computational method to handle arbitrarily complex systems. To demonstrate this approach, we collected a multidimensional fluorescence landscape of an engineered fluorescent glucose biosensor and showed that its features could be modeled with ten intricately linked ligand-binding and conformational exchange reactions. This protein represents a minimalist model of sufficient complexity to encompass fundamental biomolecular structure-function relationships: two-state and multistate conformational ensembles, conformational hierarchies, osmolytes, coupling between different binding sites and coupling between ligand binding and conformational change. The successful fit of this complex, multifaceted system demonstrates generality of the method.
Collapse
Affiliation(s)
- Malin J Allert
- Department of Biochemistry, Duke University Medical Center, Box 3711, Durham, NC, 27710, USA
| | - Homme W Hellinga
- Department of Biochemistry, Duke University Medical Center, Box 3711, Durham, NC, 27710, USA.
| |
Collapse
|
8
|
Cormann KU, Baumgart M, Bott M. Structure-Based Design of Versatile Biosensors for Small Molecules Based on the PAS Domain of a Thermophilic Histidine Kinase. ACS Synth Biol 2018; 7:2888-2897. [PMID: 30525476 DOI: 10.1021/acssynbio.8b00348] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The development of biosensors for in vitro quantification of small molecules such as metabolites or man-made chemicals is still a major challenge. Here we show that engineered variants of the sensory PAS domain of the histidine kinase CitA of the thermophilic bacterium Geobacillus thermoleovorans represent promising alternatives to established biorecognition elements. By combining binding site grafting and rational design we constructed protein variants binding l-malate, ethylmalonate, or the aromatic compound phthalate instead of the native ligand citrate. Due to more favorable entropy contributions, the wild-type protein and its engineered variants exhibited increased (nano- to micromolar) affinities and improved enantioselectivity compared to CitA homologues of mesophilic organisms. Ligand binding was directly converted into an optical signal that was preserved after immobilization of the protein. A fluorescently labeled variant was used to quantify ethylmalonate, an urinary biomarker for ethylmalonic encephalopathy, in synthetic urine, thereby demonstrating the applicability of the sensor in complex samples.
Collapse
Affiliation(s)
- Kai U. Cormann
- IBG-1: Biotechnology, Institute of Bio- and Geosciences, Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Meike Baumgart
- IBG-1: Biotechnology, Institute of Bio- and Geosciences, Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Michael Bott
- IBG-1: Biotechnology, Institute of Bio- and Geosciences, Forschungszentrum Jülich, 52425 Jülich, Germany
| |
Collapse
|
9
|
Preformulation Characterization, Stabilization, and Formulation Design for the Acrylodan-Labeled Glucose-Binding Protein SM4-AC. J Pharm Sci 2017; 106:1197-1210. [DOI: 10.1016/j.xphs.2017.01.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Revised: 12/20/2016] [Accepted: 01/03/2017] [Indexed: 11/18/2022]
|
10
|
Hickey JM, Sahni N, Chaudhuri R, D'Souza A, Metters A, Joshi SB, Russell Middaugh C, Volkin DB. Effect of acrylodan conjugation and forced oxidation on the structural integrity, conformational stability, and binding activity of a glucose binding protein SM4 used in a prototype continuous glucose monitor. Protein Sci 2017; 26:527-535. [PMID: 27997712 DOI: 10.1002/pro.3102] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2016] [Revised: 12/12/2016] [Accepted: 12/14/2016] [Indexed: 12/17/2022]
Abstract
Continuous glucose monitoring (CGM) devices offer diabetes patients a convenient approach to assist in controlling blood glucose levels. A prototype CGM has been developed that uses the emission profile of a polarity-sensitive fluorophore (acrylodan) conjugated to a glucose/galactose-binding protein (SM4-AC) to measure the concentration of glucose in vivo. During development, a decrease in the devices signal intensity was observed in vivo over time, which was postulated to be result of oxidative degradation of SM4-AC. A comprehensive physicochemical analysis of SM4-AC was pursued to identify potential mechanisms of signal intensity loss in this CGM during in vitro forced oxidation studies. An assessment of the structural integrity and conformational stability of SM4-AC indicated a relatively decreased polarity and lower tertiary structure stability compared to unconjugated protein (SM4). The stability and polarity of SM4-AC was also altered in the presence of H2 O2 . Furthermore, a time-dependent loss in the fluorescence signal of SM4-AC was observed when incubated with H2 O2 . An LC-MS peptide mapping analysis of these protein samples indicated that primarily two Met residues in SM4-AC were susceptible to oxidation. When these two residues were genetically altered to an amino acid not prone to oxidation, the glucose binding ability of the protein was retained and no loss of acrylodan fluorescence was observed in the presence of H2 O2 . Genetic alteration of these two residues is proposed as an effective approach to increase the long-term stability of SM4-AC within this prototype CGM in vivo.
Collapse
Affiliation(s)
- John M Hickey
- Department of Pharmaceutical Chemistry, Macromolecule and Vaccine Stabilization Center, University of Kansas, Lawrence, Kansas, 66047
| | - Neha Sahni
- Department of Pharmaceutical Chemistry, Macromolecule and Vaccine Stabilization Center, University of Kansas, Lawrence, Kansas, 66047
| | - Rajoshi Chaudhuri
- Department of Pharmaceutical Chemistry, Macromolecule and Vaccine Stabilization Center, University of Kansas, Lawrence, Kansas, 66047
| | - Ajit D'Souza
- BD Medical - Diabetes Care, Andover, Massachusetts, 01810
| | - Andrew Metters
- BD Medical - Diabetes Care, Andover, Massachusetts, 01810
| | - Sangeeta B Joshi
- Department of Pharmaceutical Chemistry, Macromolecule and Vaccine Stabilization Center, University of Kansas, Lawrence, Kansas, 66047
| | - C Russell Middaugh
- Department of Pharmaceutical Chemistry, Macromolecule and Vaccine Stabilization Center, University of Kansas, Lawrence, Kansas, 66047
| | - David B Volkin
- Department of Pharmaceutical Chemistry, Macromolecule and Vaccine Stabilization Center, University of Kansas, Lawrence, Kansas, 66047
| |
Collapse
|
11
|
El-Sayed MMH, Brown SR, Mupparapu K, Tolosa L. The effect of pH on the glucose response of the glucose-galactose binding protein L255C labeled with Acrylodan. Int J Biol Macromol 2016; 86:282-7. [PMID: 26812111 DOI: 10.1016/j.ijbiomac.2016.01.077] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Revised: 01/18/2016] [Accepted: 01/21/2016] [Indexed: 11/16/2022]
Abstract
The glucose-galactose binding protein (GGBP) is used as an optical biosensor in medical and bioprocess applications. This paper investigates the effect of pH on the behavior of GGBP-L255C labeled with Acrylodan for the purpose of finding the optimum conditions for sensing purposes as well as for protein preparation, purification and storage. The Acrylodan-GGBP fluorescence response in absence and presence of glucose was measured under varying buffer and pH conditions. Dissociation constants (Kd) and Gibbs free energies (ΔG) for the protein-glucose binding were calculated. Binding was found to be energetically favored at slightly acidic to neutral conditions, specifically close to the pI of GBP (∼ 5.0). Minimal fluorescence response to glucose was exhibited at pH 3.0 accompanied by a blue shift in the steady state fluorescence spectrum. In contrast, an almost 45% response to glucose was shown at pH 4.5-9.0 with a 13-nm red shift. Frequency domain lifetime measurements and quenching with KI suggest that at highly acidic conditions both the glucose-free and the glucose-bound protein are in a conformation distinct from those observed at higher pH values.
Collapse
Affiliation(s)
- Mayyada M H El-Sayed
- Center for Advanced Sensor Technology, Department of Chemical and Biochemical Engineering, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, United States.
| | - Sheniqua R Brown
- Center for Advanced Sensor Technology, Department of Chemical and Biochemical Engineering, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, United States.
| | - KarunaSri Mupparapu
- Center for Advanced Sensor Technology, Department of Chemical and Biochemical Engineering, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, United States.
| | - Leah Tolosa
- Center for Advanced Sensor Technology, Department of Chemical and Biochemical Engineering, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, United States.
| |
Collapse
|
12
|
Gifford R. Continuous glucose monitoring: 40 years, what we've learned and what's next. Chemphyschem 2013; 14:2032-44. [PMID: 23649735 DOI: 10.1002/cphc.201300172] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Indexed: 01/05/2023]
Abstract
After 40 years of research and development, today continuous glucose monitoring (CGM) is demonstrating the benefit it provides for millions with diabetes. To provide in vivo accuracy, new permselective membranes and mediated systems have been developed to prevent enzyme saturation and to minimize interference signals. Early in vivo implanted sensor research clearly showed that the foreign body response was a more difficult issue to overcome. Understanding the biological interface and circumventing the inflammatory response continue to drive development of a CGM sensor with accuracy and reliability performance suitable in a closed-loop artificial pancreas. Along with biocompatible polymer development, other complimentary algorithm and data analysis techniques have improved the performance of commercial systems significantly. For example, the mean average relative difference of Dexcom's CGM system improved from 26 to 14% and its use-life was extended from 3 to 7 d. Significant gains in usability, including size, flexibility, insertion, calibration, and data interface, have been incorporated into new generations of commercial CGM systems. Besides Medtronic, Dexcom, and Abbott, other major players are also investing in CGM. Becton Dickinson is conducting clinical trials with an optical galactose glucose binding system. Development of fully implanted sensor systems fulfills the desire for a discreet, reliable CGM system. Research continues to find innovative ways to help make living with diabetes easier and more normal, and new segments are being pursued (intensive care unit, surgery, behavior modification) in which CGM is being utilized.
Collapse
Affiliation(s)
- Raeann Gifford
- Life Science, Acreo Swedish ICT AB, Box 787 SE-601 17 Norrköping, Sweden.
| |
Collapse
|
13
|
Hsieh HV, Sherman DB, Andaluz SA, Amiss TJ, Pitner JB. Fluorescence resonance energy transfer glucose sensor from site-specific dual labeling of glucose/galactose binding protein using ligand protection. J Diabetes Sci Technol 2012; 6:1286-95. [PMID: 23294773 PMCID: PMC3570868 DOI: 10.1177/193229681200600607] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Site-selective modification of proteins at two separate locations using two different reagents is highly desirable for biosensor applications employing fluorescence resonance energy transfer (FRET), but few strategies are available for such modification. To address this challenge, sequential selective modification of two cysteines in glucose/galactose binding protein (GGBP) was demonstrated using a technique we call "ligand protection." METHOD In this technique, two cysteines were introduced in GGBP and one cysteine is rendered inaccessible by the presence of glucose, thus allowing sequential attachment of two different thiol-reactive reagents. The mutant E149C/A213C/L238S was first labeled at E149C in the presence of the ligand glucose. Following dialysis and removal of glucose, the protein was labeled with a second dye, either Texas Red (TR) C5 bromoacetamide or TR C2 maleimide, at the second site, A213C. RESULTS Changes in glucose-dependent fluorescence were observed that were consistent with FRET between the nitrobenzoxadiazole and TR fluorophores. Comparison of models and spectroscopic properties of the C2 and C5 TR FRET constructs suggests the greater rigidity of the C2 linker provides more efficient FRET. CONCLUSIONS The ligand protection strategy provides a simple method for labeling GGBP with two different fluorophores to construct FRET-based glucose sensors with glucose affinity within the human physiological glucose range (1-30 mM). This general strategy may also have broad utility for other protein-labeling applications.
Collapse
Affiliation(s)
- Helen V Hsieh
- BD Technologies, Research Triangle Park, NC 27709, USA.
| | | | | | | | | |
Collapse
|
14
|
Anastasova S, Spehar-Délèze AM, Bickham D, Uebel P, Schmidt M, Russell P, Vadgama P. Stabilised Biosensing Using Needle-Based Recess Electrodes. ELECTROANAL 2011. [DOI: 10.1002/elan.201100511] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
|