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Grosskopf JD, Sidabras JW, Altenbach C, Anderson JR, Mett RR, Strangeway RA, Hyde JS, Hubbell WL, Lerch MT. A pressure-jump EPR system to monitor millisecond conformational exchange rates of spin-labeled proteins. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.07.593074. [PMID: 38766191 PMCID: PMC11100676 DOI: 10.1101/2024.05.07.593074] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2024]
Abstract
Site-directed spin labeling electron paramagnetic resonance (SDSL-EPR) using nitroxide spin labels is a well-established technology for mapping site-specific secondary and tertiary structure and for monitoring conformational changes in proteins of any degree of complexity, including membrane proteins, with high sensitivity. SDSL-EPR also provides information on protein dynamics in the time scale of ps-µs using continuous wave lineshape analysis and spin lattice relaxation time methods. However, the functionally important time domain of µs-ms, corresponding to large-scale protein motions, is inaccessible to those methods. To extend SDSL-EPR to the longer time domain, the perturbation method of pressure-jump relaxation is implemented. Here, we describe a complete high-pressure EPR system at Q-band for both static pressure and millisecond-timescale pressure-jump measurements on spin-labeled proteins. The instrument enables pressure jumps both up and down from any holding pressure, ranging from atmospheric pressure to the maximum pressure capacity of the system components (~3500 bar). To demonstrate the utility of the system, we characterize a local folding-unfolding equilibrium of T4 lysozyme. The results illustrate the ability of the system to measure thermodynamic and kinetic parameters of protein conformational exchange on the millisecond timescale.
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Affiliation(s)
- Julian D Grosskopf
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Jason W Sidabras
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Christian Altenbach
- Department of Chemistry and Biochemistry and Stein Eye Institute, University of California, Los Angeles, CA 90095, USA
| | - Jim R Anderson
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Richard R Mett
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Robert A Strangeway
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - James S Hyde
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Wayne L Hubbell
- Department of Chemistry and Biochemistry and Stein Eye Institute, University of California, Los Angeles, CA 90095, USA
| | - Michael T Lerch
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI 53226, USA
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2
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Jaufer AM, Bouhadana A, Kharrazizadeh A, Zhou M, Colina CM, Fanucci GE. Designing surface exposed sites on Bacillus subtilis lipase A for spin-labeling and hydration studies. Biophys Chem 2024; 308:107203. [PMID: 38382282 DOI: 10.1016/j.bpc.2024.107203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2024] [Revised: 02/09/2024] [Accepted: 02/15/2024] [Indexed: 02/23/2024]
Abstract
Spin-labeling with electron paramagnetic resonance spectroscopy (EPR) is a facile method for interrogating macromolecular flexibility, conformational changes, accessibility, and hydration. Within we present a computationally based approach for the rational selection of reporter sites in Bacillus subtilis lipase A (BSLA) for substitution to cysteine residues with subsequent modification with a spin-label that are expected to not significantly perturb the wild-type structure, dynamics, or enzymatic function. Experimental circular dichroism spectroscopy, Michaelis-Menten kinetic parameters and EPR spectroscopy data validate the success of this approach to computationally select reporter sites for future magnetic resonance investigations of hydration and hydration changes induced by polymer conjugation, tethering, immobilization, or amino acid substitution in BSLA. Analysis of molecular dynamic simulations of the impact of substitutions on the secondary structure agree well with experimental findings. We propose that this computationally guided approach for choosing spin-labeled EPR reporter sites, which evaluates relative surface accessibility coupled with hydrogen bonding occupancy of amino acids to the catalytic pocket via atomistic simulations, should be readily transferable to other macromolecular systems of interest including selecting sites for paramagnetic relaxation enhancement NMR studies, other spin-labeling EPR studies or any method requiring a tagging method where it is desirable to not alter enzyme stability or activity.
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Affiliation(s)
- Afnan M Jaufer
- Department of Chemistry, University of Florida, PO BOX 117200, Gainesville, FL 32611, USA; George and Josephine Butler Polymer Research Laboratory, University of Florida, Gainesville, FL 32611, USA.
| | - Adam Bouhadana
- Department of Chemistry, University of Florida, PO BOX 117200, Gainesville, FL 32611, USA.
| | - Amir Kharrazizadeh
- Department of Chemistry, University of Florida, PO BOX 117200, Gainesville, FL 32611, USA.
| | - Mingwei Zhou
- Department of Chemistry, University of Florida, PO BOX 117200, Gainesville, FL 32611, USA.
| | - Coray M Colina
- Department of Chemistry, University of Florida, PO BOX 117200, Gainesville, FL 32611, USA; George and Josephine Butler Polymer Research Laboratory, University of Florida, Gainesville, FL 32611, USA; Department of Materials Science and Engineering, University of Florida, PO BOX 117200, Gainesville, FL 32611, USA.
| | - Gail E Fanucci
- Department of Chemistry, University of Florida, PO BOX 117200, Gainesville, FL 32611, USA.
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3
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Jaiswal M, Tran TT, Guo J, Zhou M, Kundu S, Guo Z, Fanucci GE. Spin-labeling Insights into How Chemical Fixation Impacts Glycan Organization on Cells. APPLIED MAGNETIC RESONANCE 2024; 55:317-333. [PMID: 38469359 PMCID: PMC10927023 DOI: 10.1007/s00723-023-01624-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2023] [Revised: 09/21/2023] [Accepted: 09/22/2023] [Indexed: 03/13/2024]
Abstract
As new methods to interrogate glycan organization on cells develop, it is important to have a molecular level understanding of how chemical fixation can impact results and interpretations. Site-directed spin labeling technologies are well suited to study how the spin label mobility is impacted by local environmental conditions, such as those imposed by cross-linking effects of paraformaldehyde cell fixation methods. Here, we utilize three different azide-containing sugars for metabolic glycan engineering with HeLa cells to incorporate azido glycans that are modified with a DBCO-based nitroxide moiety via click reaction. Continuous wave X-band electron paramagnetic resonance spectroscopy is employed to characterize how the chronological sequence of chemical fixation and spin labeling impacts the local mobility and accessibility of the nitroxide-labeled glycans in the glycocalyx of HeLa cells. Results demonstrate that chemical fixation with paraformaldehyde can alter local glycan mobility and care should be taken in the analysis of data in any study where chemical fixation and cellular labeling occur.
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Affiliation(s)
- Mohit Jaiswal
- Department of Chemistry, University of Florida, 214 Leigh Hall, Gainesville, FL 32611, USA
| | - Trang T Tran
- Department of Chemistry, University of Florida, 214 Leigh Hall, Gainesville, FL 32611, USA
| | - Jiatong Guo
- Department of Chemistry, University of Florida, 214 Leigh Hall, Gainesville, FL 32611, USA
| | - Mingwei Zhou
- Department of Chemistry, University of Florida, 214 Leigh Hall, Gainesville, FL 32611, USA
| | - Sayan Kundu
- Department of Chemistry, University of Florida, 214 Leigh Hall, Gainesville, FL 32611, USA
| | - Zhongwu Guo
- Department of Chemistry, University of Florida, 214 Leigh Hall, Gainesville, FL 32611, USA
| | - Gail E Fanucci
- Department of Chemistry, University of Florida, 214 Leigh Hall, Gainesville, FL 32611, USA
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4
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Li Q, Lenertz M, Armstrong Z, MacRae A, Feng L, Ugrinov A, Yang Z. A Protocol to Depict the Proteolytic Processes Using a Combination of Metal-Organic Materials (MOMs), Electron Paramagnetic Resonance (EPR), and Mass Spectrometry (MS). Bio Protoc 2024; 14:e4909. [PMID: 38213322 PMCID: PMC10777052 DOI: 10.21769/bioprotoc.4909] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Revised: 11/20/2023] [Accepted: 11/21/2023] [Indexed: 01/13/2024] Open
Abstract
Proteolysis is a critical biochemical process yet a challenging field to study experimentally due to the self-degradation of a protease and the complex, dynamic degradation steps of a substrate. Mass spectrometry (MS) is the traditional way for proteolytic studies, yet it is challenging when time-resolved, step-by-step details of the degradation process are needed. We recently found a way to resolve the cleavage site, preference/selectivity of cleavage regions, and proteolytic kinetics by combining site-directed spin labeling (SDSL) of protein substrate, time-resolved two-dimensional (2D) electron paramagnetic resonance (EPR) spectroscopy, protease immobilization via metal-organic materials (MOMs), and MS. The method has been demonstrated on a model substrate and protease, yet there is a lack of details on the practical operations to carry out our strategy. Thus, this protocol summarizes the key steps and considerations when carrying out the EPR/MS study on proteolytic processes, which can be generalized to study other protein/polypeptide substrates in proteolysis. Details for the experimental operation and cautions of each step are reported with figures illustrating the concepts. This protocol provides an effective approach to understanding the proteolytic process with the advantages of offering time-resolved, residue-level resolution of structural basis underlying the process. Such information is important for revealing the cleavage site and proteolytic mechanisms of unknown proteases. The advantage of EPR, probing the target substrate regardless of the complexities caused by the proteases and their self-degradation, offers a practically effective, rapid, and easy-to-operate approach to studying proteolysis. Key features • Combining protease immobilization, EPR, spin labeling, and MS experimental methods allows for the analysis of proteolysis process in real time. • Reveals cleavage site, kinetics of product generation, and preference of cleavage regions via time-resolved SDSL-EPR. • MS confirms EPR findings and helps depict the sequences and populations of the cleaved segments in real time. • The demonstrated method can be generalized to other proteins or polypeptide substrates upon proteolysis by other proteases.
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Affiliation(s)
- Qiaobin Li
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND, 58102, USA
| | - Mary Lenertz
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND, 58102, USA
| | - Zoe Armstrong
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND, 58102, USA
| | - Austin MacRae
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND, 58102, USA
| | - Li Feng
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND, 58102, USA
| | - Angel Ugrinov
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND, 58102, USA
| | - Zhongyu Yang
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND, 58102, USA
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Armstrong Z, MacRae A, Lenertz M, Li Q, Johnson K, Scheiwiller A, Shen P, Feng L, Quadir M, Yang Z. Impact of Crystallinity on Enzyme Orientation and Dynamics upon Biomineralization in Metal-Organic Frameworks. ACS APPLIED MATERIALS & INTERFACES 2023; 15:38124-38131. [PMID: 37494658 DOI: 10.1021/acsami.3c07870] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/28/2023]
Abstract
Aqueous-phase co-crystallization (also known as biomimetic mineralization or biomineralization) is a unique way to encapsulate large enzymes, enzyme clusters, and enzymes with large substrates in metal-organic frameworks (MOFs), broadening the application of MOFs as enzyme carriers. The crystallinity of resultant enzyme@MOF biocomposites, however, can be low, raising a concern about how MOF crystal packing quality affects enzyme performance upon encapsulation. The challenges to overcome this concern are (1) the limited database of enzyme performance upon biomineralization in different aqueous MOFs and (2) the difficulty in probing enzyme restriction and motion in the resultant MOF scaffolds, which are related to the local crystal packing quality/density, under the interference of the MOF backgrounds. We have discovered several new aqueous MOFs for enzyme biomineralization with varied crystallinity [Jordahl, D.; Armstrong, Z.; Li, Q.; Gao, R.; Liu, W.; Johnson, K.; Brown, W.; Scheiwiller, A.; Feng, L.; Ugrinov, A.; Mao, H.; Chen, B.; Quadir, M.; Pan, Y.; Li, H.; Yang, Z. Expanding the Library of Metal-Organic Frameworks (MOFs) for Enzyme Biomineralization. ACS Appl. Mater. Interfaces 2022, 14 (46), 51619-51629, DOI: 10.1021/acsami.2c12998]. Here, we address the second challenge by probing enzyme dynamics/restriction in these MOFs at the residue level via site-directed spin labeling (SDSL)-electron paramagnetic resonance (EPR) spectroscopy, a unique approach to determine protein backbone motions regardless of the background complexity. We encapsulated a model large-substrate enzyme, lysozyme, in eight newly discovered MOFs, which possess various degrees of crystallization, via aqueous-phase co-crystallization. Through the EPR study and simulations, we found rough connections between (a) enzyme mobility/dynamics and MOF crystal properties (packing quality and density) and (b) enzyme areas exposed above each MOF and their catalytic performance. This work suggests that protein SDSL and EPR can serve as an indicator of MOF crystal packing quality/density when biomineralized in MOFs. The method can be generalized to probing the dynamics of other enzymes on other solid surfaces/interfaces and guide the rational design of solid platforms (ca. MOFs) to customize enzyme immobilization.
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Affiliation(s)
- Zoe Armstrong
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58102, United States
| | - Austin MacRae
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58102, United States
| | - Mary Lenertz
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58102, United States
| | - Qiaobin Li
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58102, United States
| | - Kelley Johnson
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58102, United States
| | - Allison Scheiwiller
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58102, United States
| | - Patrick Shen
- Davis High School, Fargo, North Dakota 58104, United States
| | - Li Feng
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58102, United States
| | - Mohiuddin Quadir
- Department of Coatings and Polymeric Materials, North Dakota State University, Fargo, North Dakota 58102, United States
| | - Zhongyu Yang
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58102, United States
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Jaiswal M, Tran TT, Guo J, Zhou M, Kunda S, Guo Z, Fanucci G. Spin-labeling Insights into How Chemical Fixation Impacts Glycan Organization on Cells. RESEARCH SQUARE 2023:rs.3.rs-3039983. [PMID: 37398188 PMCID: PMC10312935 DOI: 10.21203/rs.3.rs-3039983/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/04/2023]
Abstract
As new methods to interrogate glycan organization on cells develop, it is important to have a molecular level understanding of how chemical fixation can impact results and interpretations. Site-directed spin labeling technologies are well suited to study how the spin label mobility is impacted by local environmental conditions, such as those imposed by cross-linking effects of paraformaldehyde cell fixation methods. Here, we utilize three different azide-containing sugars for metabolic glycan engineering with HeLa cells to incorporate azido glycans that are modified with a DBCO-based nitroxide moiety via click reaction. Continuous wave X-band electron paramagnetic resonance spectroscopy is employed to characterize how the chronological sequence of chemical fixation and spin labeling impacts the local mobility and accessibility of the nitroxide-labeled glycans in the glycocalyx of HeLa cells. Results demonstrate that chemical fixation with paraformaldehyde can alter local glycan mobility and care should be taken in the analysis of data in any study where chemical fixation and cellular labeling occur.
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7
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Ma L, Li X, Petersen RB, Peng A, Huang K. Probing the interactions between amyloidogenic proteins and bio-membranes. Biophys Chem 2023; 296:106984. [PMID: 36889133 DOI: 10.1016/j.bpc.2023.106984] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Revised: 02/11/2023] [Accepted: 02/22/2023] [Indexed: 03/01/2023]
Abstract
Protein misfolding diseases (PMDs) in humans are characterized by the deposition of protein aggregates in tissues, including Alzheimer's disease, Parkinson's disease, type 2 diabetes, and amyotrophic lateral sclerosis. Misfolding and aggregation of amyloidogenic proteins play a central role in the onset and progression of PMDs, and these processes are regulated by multiple factors, especially the interaction between proteins and bio-membranes. Bio-membranes induce conformational changes in amyloidogenic proteins and affect their aggregation; on the other hand, the aggregates of amyloidogenic proteins may cause membrane damage or dysfunction leading to cytotoxicity. In this review, we summarize the factors that affect the binding of amyloidogenic proteins and membranes, the effects of bio-membranes on the aggregation of amyloidogenic proteins, mechanisms of membrane disruption by amyloidogenic aggregates, technical approaches for detecting these interactions, and finally therapeutic strategies targeting membrane damage caused by amyloidogenic proteins.
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Affiliation(s)
- Liang Ma
- Department of Pharmacy, Wuhan Mental Health Center, Wuhan, China; Department of Pharmacy, Wuhan Hospital for Psychotherapy, Wuhan, China
| | - Xi Li
- Tongji School of Pharmacy, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Robert B Petersen
- Foundational Sciences, Central Michigan University College of Medicine, Mount Pleasant, MI, USA
| | - Anlin Peng
- Department of Pharmacy, The Third Hospital of Wuhan, Tongren Hospital of Wuhan University, Wuhan, China.
| | - Kun Huang
- Tongji School of Pharmacy, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
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8
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Pan Y, Li Q, Liu W, Armstrong Z, MacRae A, Feng L, McNeff C, Zhao P, Li H, Yang Z. Unveiling the orientation and dynamics of enzymes in unstructured artificial compartments of metal-organic frameworks (MOFs). NANOSCALE 2023; 15:2573-2577. [PMID: 36655708 DOI: 10.1039/d2nr06659a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Confining enzymes in well-shaped MOF compartments is a promising approach to mimic the cellular environment of enzymes and determine enzyme structure-function relationship therein. Under the cellular crowding, however, enzymes can also be confined in unstructured spaces that are close to the shapes/outlines of the enzyme. Therefore, for a better understanding of enzymes in their physiological environments, it is necessary to study enzymes in these unstructured spaces. However, practically it is challenging to create compartments that are close to the outline of an enzyme and probe enzyme structural information therein. Here, for proof-of-principle, we confined a model enzyme, lysozyme, in the crystal defects of a MOF via co-crystallization, where lysozyme served as the nuclei for MOF crystal scaffolds to grow on so that unstructured spaces close to the outline of lysozyme are created, and determined enzyme relative orientation and dynamics. This effort is important for understanding enzymes in near-native environments and guiding the rational design of biocatalysts that mimic how nature confines enzymes.
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Affiliation(s)
- Yanxiong Pan
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, 130022, China.
| | - Qiaobin Li
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND, 58108, USA
| | - Wei Liu
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, 130022, China.
| | - Zoe Armstrong
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND, 58108, USA
| | - Austin MacRae
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND, 58108, USA
| | - Li Feng
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND, 58108, USA
| | - Charles McNeff
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND, 58108, USA
| | - Pinjing Zhao
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND, 58108, USA
| | - Hui Li
- Department of Plant Sciences, North Dakota State University, Fargo, ND, 58108, USA.
| | - Zhongyu Yang
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND, 58108, USA
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Structure-Based Function and Regulation of NCX Variants: Updates and Challenges. Int J Mol Sci 2022; 24:ijms24010061. [PMID: 36613523 PMCID: PMC9820601 DOI: 10.3390/ijms24010061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2022] [Revised: 12/14/2022] [Accepted: 12/15/2022] [Indexed: 12/24/2022] Open
Abstract
The plasma-membrane homeostasis Na+/Ca2+ exchangers (NCXs) mediate Ca2+ extrusion/entry to dynamically shape Ca2+ signaling/in biological systems ranging from bacteria to humans. The NCX gene orthologs, isoforms, and their splice variants are expressed in a tissue-specific manner and exhibit nearly 104-fold differences in the transport rates and regulatory specificities to match the cell-specific requirements. Selective pharmacological targeting of NCX variants could benefit many clinical applications, although this intervention remains challenging, mainly because a full-size structure of eukaryotic NCX is unavailable. The crystal structure of the archaeal NCX_Mj, in conjunction with biophysical, computational, and functional analyses, provided a breakthrough in resolving the ion transport mechanisms. However, NCX_Mj (whose size is nearly three times smaller than that of mammalian NCXs) cannot serve as a structure-dynamic model for imitating high transport rates and regulatory modules possessed by eukaryotic NCXs. The crystal structures of isolated regulatory domains (obtained from eukaryotic NCXs) and their biophysical analyses by SAXS, NMR, FRET, and HDX-MS approaches revealed structure-based variances of regulatory modules. Despite these achievements, it remains unclear how multi-domain interactions can decode and integrate diverse allosteric signals, thereby yielding distinct regulatory outcomes in a given ortholog/isoform/splice variant. This article summarizes the relevant issues from the perspective of future developments.
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Site directed spin labeling to elucidating the mechanism of the cyanobacterial circadian clock. Methods Enzymol 2022; 666:59-78. [PMID: 35465929 DOI: 10.1016/bs.mie.2022.02.011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Electron Paramagnetic Resonance (EPR) is a spectroscopic technique that provides structural and dynamic information on unpaired spins and their surrounding environments. Introduction of exogenous spin labels via site directed spin labeling (SDSL) enables characterization of systems of interests lacking intrinsic unpaired spins. This chapter describes the use of SDSL in quantifying KaiB-KaiC binding in the cyanobacterial circadian clock (Kai Clock), exploiting the changes in mobility of the local environment around the spin label on KaiB-KaiC interactions. While the Kai system serves as our model system to demonstrate SDSL-EPR utility in quantifying protein-protein interactions, this technique is readily amenable to other systems of interest whenever specific protein-protein interactions need to be isolated. We first present a protocol for spin labeling KaiB. Then, we detail the sample preparation and acquisition processes to maximize signal-to-noise for downstream analysis. We close this chapter by highlighting recent advances in SDSL technology to incorporate spin labels into proteins of interest and in EPR technology to improve detection sensitivity that may allow greater flexibilities to the types of experiments possible.
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Xiao H, Duo L, Zhen J, Wang H, Guo Z. Static and dynamic disorder in Aβ40 fibrils. Biochem Biophys Res Commun 2022; 610:107-112. [PMID: 35461071 DOI: 10.1016/j.bbrc.2022.04.036] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Accepted: 04/08/2022] [Indexed: 12/01/2022]
Abstract
Deposition of Aβ aggregates in the form of amyloid fibrils is a pathological hallmark of Alzheimer's disease. Understanding the structure and dynamics of Aβ fibrils is important for delineating the mechanism of Aβ aggregation and developing effective therapeutic strategies. Here we used site-directed spin labeling and EPR spectroscopy to study the Aβ40 fibril structure and dynamics. We obtained the EPR spectra of 40 spin-labeled Aβ40 fibril samples, with spin labeling coverage of the entire Aβ40 sequence. Analysis of the spin exchange interaction and spin label mobility using spectral simulations suggest that the strength of spin exchange interaction is primarily determined by static disorder in the Aβ40 fibrils. EPR data suggest that the entire Aβ40 sequence except residue D1 is highly ordered and the two hydrophobic regions at residues 17-20 and 31-36 show the lowest static disorder. Dynamic disorder is relatively constant across all reside positions, with residues 22 and 23 having the highest dynamic disorder. Comparison of the EPR data for Aβ40 and Aβ42 fibrils shows overall more ordered packing interactions in Aβ40 fibrils. Another noteworthy difference is the C-terminal residue, which has high static disorder in Aβ42 fibrils, but is ordered in Aβ40 fibrils. The higher static disorder in Aβ42 fibrils may lead to increased fragmentation, monomer dissociation, and structural defects, which may contribute to increased aggregation through secondary nucleation.
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Affiliation(s)
- Hui Xiao
- Department of Neurology, Brain Research Institute, Molecular Biology Institute, University of California, Los Angeles, CA, 90095, USA
| | - Lan Duo
- Department of Neurology, Brain Research Institute, Molecular Biology Institute, University of California, Los Angeles, CA, 90095, USA
| | - James Zhen
- Department of Neurology, Brain Research Institute, Molecular Biology Institute, University of California, Los Angeles, CA, 90095, USA
| | - Hongsu Wang
- Department of Neurology, Brain Research Institute, Molecular Biology Institute, University of California, Los Angeles, CA, 90095, USA
| | - Zhefeng Guo
- Department of Neurology, Brain Research Institute, Molecular Biology Institute, University of California, Los Angeles, CA, 90095, USA.
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12
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Liu EN, Park G, Nohara J, Guo Z. Effect of spin labelling on the aggregation kinetics of yeast prion protein Ure2. ROYAL SOCIETY OPEN SCIENCE 2021; 8:201747. [PMID: 33959337 PMCID: PMC8074925 DOI: 10.1098/rsos.201747] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Accepted: 02/10/2021] [Indexed: 06/12/2023]
Abstract
Amyloid formation is involved in a wide range of neurodegenerative diseases including Alzheimer's and prion diseases. Structural understanding of the amyloid is critical to delineate the mechanism of aggregation and its pathological spreading. Site-directed spin labelling has emerged as a powerful structural tool in the studies of amyloid structures and provided structural evidence for the parallel in-register β-sheet structure for a wide range of amyloid proteins. It is generally accepted that spin labelling does not disrupt the structure of the amyloid fibrils, the end product of protein aggregation. The effect on the rate of protein aggregation, however, has not been well characterized. Here, we employed a scanning mutagenesis approach to study the effect of spin labelling on the aggregation rate of 79 spin-labelled variants of the Ure2 prion domain. The aggregation of Ure2 protein is the basis of yeast prion [URE3]. We found that all spin-labelled Ure2 mutants aggregated within the experimental timeframe of 15 to 40 h. Among the 79 spin-labelled positions, only five residue sites (N23, N27, S33, I35 and G42) showed a dramatic delay in the aggregation rate as a result of spin labelling. These positions may be important for fibril nucleation, a rate-limiting step in aggregation. Importantly, spin labelling at most of the sites had a muted effect on Ure2 aggregation kinetics, showing a general tolerance of spin labelling in protein aggregation studies.
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Affiliation(s)
- Emilie N. Liu
- Department of Neurology, Brain Research Institute, Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA
| | - Giovanna Park
- Department of Neurology, Brain Research Institute, Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA
| | - Junsuke Nohara
- Department of Neurology, Brain Research Institute, Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA
| | - Zhefeng Guo
- Department of Neurology, Brain Research Institute, Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA
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13
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Yoon A, Zhen J, Guo Z. Segmental structural dynamics in Aβ42 globulomers. Biochem Biophys Res Commun 2021; 545:119-124. [PMID: 33548624 DOI: 10.1016/j.bbrc.2021.01.081] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Accepted: 01/23/2021] [Indexed: 02/06/2023]
Abstract
Aβ42 aggregation plays a central role in the pathogenesis of Alzheimer's disease. In addition to the insoluble fibrils that comprise the amyloid plaques, Aβ42 also forms soluble aggregates collectively called oligomers, which are more toxic and pathogenic than fibrils. Understanding the structure and dynamics of Aβ42 oligomers is critical for developing effective therapeutic interventions against these oligomers. Here we studied the structural dynamics of Aβ42 globulomers, a type of Aβ42 oligomers prepared in the presence of sodium dodecyl sulfate, using site-directed spin labeling. Spin labels were introduced, one at a time, at all 42 residue positions of Aβ42 sequence. Electron paramagnetic resonance spectra of spin-labeled samples reveal four structural segments based on site-dependent spin label mobility pattern. Segment-1 consists of residues 1-6, which have the highest mobility that is consistent with complete disorder. Segment-3 is the most immobilized region, including residues 31-34. Segment-2 and -4 have intermediate mobility and are composed of residues 7-30 and 35-42, respectively. Considering the inverse relationship between protein dynamics and stability, our results suggest that residues 31-34 are the most stable segment in Aβ42 oligomers. At the same time, the EPR spectral lineshape suggests that Aβ42 globulomers lack a well-packed structural core akin to that of globular proteins.
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Affiliation(s)
- Allison Yoon
- Department of Neurology, Brain Research Institute, Molecular Biology Institute, University of California, Los Angeles, CA, 90095, USA
| | - James Zhen
- Department of Neurology, Brain Research Institute, Molecular Biology Institute, University of California, Los Angeles, CA, 90095, USA
| | - Zhefeng Guo
- Department of Neurology, Brain Research Institute, Molecular Biology Institute, University of California, Los Angeles, CA, 90095, USA.
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14
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Native Cell Environment Constrains Loop Structure in the Escherichia coli Cobalamin Transporter BtuB. Biophys J 2020; 119:1550-1557. [PMID: 32946767 DOI: 10.1016/j.bpj.2020.08.034] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 08/27/2020] [Accepted: 08/31/2020] [Indexed: 11/23/2022] Open
Abstract
The extracellular loops of bacterial outer membrane (OM) transporters are thought to sample a range of conformations in the apo state but to undergo a gating motion and assume a more defined conformation upon the binding of substrate. Here, we use pulse electron paramagnetic resonance to examine the conformations of the extracellular loops of BtuB, the Escherichia coli TonB-dependent vitamin B12 transporter, in whole cells. Unlike previous measurements carried out in vitro, the loops assume well-defined configurations in situ that closely match the in surfo crystal structures. Moreover, there is no evidence that the loops undergo significant gating motions upon the binding of substrate. The results demonstrate that the structure of BtuB is dependent upon an intact native OM environment, in which a critical component is likely to be the extracellular lipopolysaccharide. In general, this work indicates that measurements on OM proteins in reconstituted membrane systems may not reflect the native state of the protein in vivo.
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15
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Sun Q, Pan Y, Wang X, Li H, Farmakes J, Aguila B, Yang Z, Ma S. Mapping out the Degree of Freedom of Hosted Enzymes in Confined Spatial Environments. Chem 2019. [DOI: 10.1016/j.chempr.2019.10.002] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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16
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Li H, Pan Y, Farmakes J, Xiao F, Liu G, Chen B, Zhu X, Rao J, Yang Z. A sulfonated mesoporous silica nanoparticle for enzyme protection against denaturants and controlled release under reducing conditions. J Colloid Interface Sci 2019; 556:292-300. [DOI: 10.1016/j.jcis.2019.08.063] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Revised: 08/15/2019] [Accepted: 08/16/2019] [Indexed: 01/23/2023]
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17
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Exploring the role of the various methionine residues in the Escherichia coli CusB adapter protein. PLoS One 2019; 14:e0219337. [PMID: 31465444 PMCID: PMC6715271 DOI: 10.1371/journal.pone.0219337] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 08/15/2019] [Indexed: 11/29/2022] Open
Abstract
The dissemination of resistant pathogenic microbes has become one of the most challenging problems that modern medicine has faced. Developing novel drugs based on new molecular targets that previously were not targeted, is therefore the highest priority in antibiotics research. One approach that has been recently suggested is to inhibit copper transporters in prokaryotic systems. Copper is required for many biological pathways, but sometimes it can harm the cell. Pathogenic systems have a highly sophisticated copper-regulation network; therefore, a better understanding of how this network operates at the molecular level should assist in developing the next generation of antibiotics. The CusB protein is part of the CusCBA periplasmic Cu(I) efflux system in Gram-negative bacteria, and was recently reported to play a key role in the functioning of the whole CusCBA system, in which conformational changes as well as the assembly/disassembly process control the opening of the transporter. More knowledge of the underlying mechanism is needed to attain a full understanding of CusB functioning, which is associated with targeting specific and crucial residues in CusB. Here, we combine in-vitro structural measurements, which use EPR spectroscopy and UV-Vis measurements, with cell experiments to explore the role of the various methionine residues in CusB. We targeted two methionine residues (M227 and M241) that are essential for the proper functioning of CusB.
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18
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Lai Y, Kuo Y, Chiang Y. Identifying Protein Conformational Dynamics Using Spin‐label ESR. Chem Asian J 2019; 14:3981-3991. [DOI: 10.1002/asia.201900855] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Revised: 08/02/2019] [Indexed: 12/24/2022]
Affiliation(s)
- Yei‐Chen Lai
- Department of Chemistry National Tsing Hua University Hsinchu 30013 Taiwan
- Department of Chemistry&Biochemistry University of California Santa Barbara CA 93106-9510 USA
| | - Yun‐Hsuan Kuo
- Department of Chemistry National Tsing Hua University Hsinchu 30013 Taiwan
| | - Yun‐Wei Chiang
- Department of Chemistry National Tsing Hua University Hsinchu 30013 Taiwan
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19
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The TonB m-PocAB System Is Required for Maintenance of Membrane Integrity and Polar Position of Flagella in Pseudomonas putida. J Bacteriol 2019; 201:JB.00303-19. [PMID: 31182498 DOI: 10.1128/jb.00303-19] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2019] [Accepted: 06/07/2019] [Indexed: 12/23/2022] Open
Abstract
TonB-ExbB-ExbD-like energy transduction systems are widespread among Gram-negative bacteria. While most species have only one copy of tonB-exbBD genes, the Pseudomonas species possess more TonB-ExbBD homologues. One of them, the TonB3-PocA-PocB complex, was recently shown to be required for polar localization of FlhF and, thus, the flagella in Pseudomonas aeruginosa Here, we show that the orthologous TonBm-PocA-PocB complex is important for polar localization of FlhF and flagella in Pseudomonas putida as well. Additionally, the system is necessary for maintaining membrane integrity, as the inactivation of the TonBm-PocAB complex results in increased membrane permeability, lowered stress tolerance, and conditional cell lysis. Interestingly, the functionality of TonBm-PocAB complex is more important for stationary than for exponentially growing bacteria. The whole-cell proteome analysis provided a likely explanation for this growth phase dependence, as extensive reprogramming was disclosed in an exponentially growing tonBm deletion strain, while only a few proteomic changes, mostly downregulation of outer membrane proteins, were determined in the stationary-phase ΔtonBm strain. We propose that this response in exponential phase, involving, inter alia, activation of AlgU and ColR regulons, can compensate for TonBm-PocAB's deficiency, while stationary-phase cells are unable to alleviate the lack of TonBm-PocAB. Our results suggest that mislocalization of flagella does not cause the membrane integrity problems; rather, the impaired membrane intactness of the TonBm-PocAB-deficient strain could be the reason for the random placement of flagella.IMPORTANCE The ubiquitous Pseudomonas species are well adapted to survive in a wide variety of environments. Their success relies on their versatile metabolic, signaling, and transport ability but also on their high intrinsic tolerance to various stress factors. This is why the study of the stress-surviving mechanisms of Pseudomonas species is of utmost importance. The stress tolerance of Pseudomonads is mainly achieved through the high barrier property of their membranes. Here, we present evidence that the TonB-ExbBD-like TonBm-PocAB system is involved in maintaining the membrane homeostasis of Pseudomonas putida, and its deficiency leads to lowered stress tolerance and conditional cell lysis.
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20
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Lawless MJ, Pettersson JR, Rule GS, Lanni F, Saxena S. ESR Resolves the C Terminus Structure of the Ligand-free Human Glutathione S-Transferase A1-1. Biophys J 2019; 114:592-601. [PMID: 29414705 DOI: 10.1016/j.bpj.2017.12.016] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Revised: 12/11/2017] [Accepted: 12/18/2017] [Indexed: 01/05/2023] Open
Abstract
Nitroxide- and Cu2+-based electron spin resonance (ESR) are combined to provide insight into the conformational states of the functionally important α-helix of the human glutathione S-transferase A1. Distance measurements on various spin-labeled dimeric human glutathione S-transferase A1-1 all result in bimodal distance distributions, indicating that the C-terminus exists in two distinct conformations in solution, one of which closely matches that found in the crystal structure of the ligand-bound enzyme. These measurements permit the generation of a model of the unliganded conformation. Room temperature ESR indicates that the second conformation has high mobility, potentially enabling the enzyme's high degree of substrate promiscuity. This model is then validated using computational modeling and further Cu2+-based ESR distance measurements. Cu2+-based ESR also provides evidence that the secondary structure of the second conformation is of helical nature. Addition of S-hexyl glutathione results in a shift in relative populations, favoring the state that is similar to the previously known structure of the ligand-bound enzyme.
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Affiliation(s)
- Matthew J Lawless
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - John R Pettersson
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania
| | - Gordon S Rule
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania
| | - Frederick Lanni
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania
| | - Sunil Saxena
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania.
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21
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Marinelli F, Fiorin G. Structural Characterization of Biomolecules through Atomistic Simulations Guided by DEER Measurements. Structure 2019; 27:359-370.e12. [PMID: 30528595 PMCID: PMC6860373 DOI: 10.1016/j.str.2018.10.013] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Revised: 09/06/2018] [Accepted: 10/18/2018] [Indexed: 11/17/2022]
Abstract
Double electron-electron resonance (DEER) is a popular technique that exploits attached spin labels to probe the collective dynamics of biomolecules in a native environment. Like most spectroscopic approaches, DEER detects an ensemble of states accounting for biomolecular dynamics as well as the labels' intrinsic flexibility. Hence, the DEER data alone do not provide high-resolution structural information. To disentangle this variability, we introduce a minimally biased simulation method to sample a structural ensemble that reproduces multiple experimental signals within the uncertainty. In contrast to previous approaches, our method targets the raw data themselves, and thereby it brings forth an unbiased molecular interpretation of the experiments. After validation on the T4 lysozyme, we apply this technique to interpret recent DEER experiments on a membrane transporter binding protein (VcSiaP). The results highlight the large-scale conformational movement that occurs upon substrate binding and reveal that the unbound VcSiaP is more open in solution than the X-ray structure.
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Affiliation(s)
- Fabrizio Marinelli
- Theoretical Molecular Biophysics Laboratory, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20814, USA.
| | - Giacomo Fiorin
- Theoretical Molecular Biophysics Laboratory, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20814, USA
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22
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Gamble Jarvi A, Ranguelova K, Ghosh S, Weber RT, Saxena S. On the Use of Q-Band Double Electron–Electron Resonance To Resolve the Relative Orientations of Two Double Histidine-Bound Cu2+ Ions in a Protein. J Phys Chem B 2018; 122:10669-10677. [DOI: 10.1021/acs.jpcb.8b07727] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- Austin Gamble Jarvi
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Kalina Ranguelova
- Bruker BioSpin, Inc., EPR Division, 15 Fortune Drive, Billerica, Massachusetts 01821, United States
| | - Shreya Ghosh
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Ralph T. Weber
- Bruker BioSpin, Inc., EPR Division, 15 Fortune Drive, Billerica, Massachusetts 01821, United States
| | - Sunil Saxena
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
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23
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Stoyanovsky AD, Stoyanovsky DA. 1-Oxo-2,2,6,6-tetramethylpiperidinium bromide converts α-H N,N-dialkylhydroxylamines to nitrones via a two-electron oxidation mechanism. Sci Rep 2018; 8:15323. [PMID: 30333514 PMCID: PMC6193029 DOI: 10.1038/s41598-018-33639-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Accepted: 10/02/2018] [Indexed: 01/13/2023] Open
Abstract
Herein we provide experimental proof that 1-oxo-2,2,6,6-tetramethylpiperidinium bromide converts α-H N,N-dialkylhydroxylamines to nitrones via a two-electron oxidation mechanism. The reactions reported are rapid, proceed under mild conditions, and afford nitrones in excellent yields.
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Affiliation(s)
| | - Detcho A Stoyanovsky
- Department of Environmental and Occupational Health, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
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24
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Gadbery JE, Sampson NS. Use of an Isotope-Coded Mass Tag (ICMT) Method To Determine the Orientation of Cholesterol Oxidase on Model Membranes. Biochemistry 2018; 57:5370-5378. [PMID: 30125103 PMCID: PMC6171977 DOI: 10.1021/acs.biochem.8b00788] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Although the interfacial membrane protein cholesterol oxidase is structurally and kinetically well-characterized, its orientation in and mode of interaction with cholesterol-containing membranes have not been established. Cholesterol oxidase can alter the structure of the cell membrane in pathogenic bacteria and is thus a potential antimicrobial drug target. We recently developed a mass spectrometry-based isotope-coded mass tag (ICMT) labeling method to monitor the real-time solvent-accessible surface of peripheral membrane proteins, such as cholesterol oxidase. The ICMT strategy utilizes maleimide-based isotope tags that covalently react with cysteine residues. In this study, by comparing the ICMT labeling rates of cysteine variants of cholesterol oxidase, we determined which residues of the protein were engaged with the protein-lipid interface. We found that upon addition of cholesterol-containing lipid vesicles, four cysteine residues in a cluster near the substrate entrance channel are labeled more slowly with ICMT probes than in the absence of vesicles, indicating that these four residues were in contact with the membrane surface. From these data, we generated a model of how cholesterol oxidase is oriented when bound to the membrane. In conclusion, this straightforward method, which requires only microgram quantities of protein, offers several advantages over existing methods for the investigation of interfacial membrane proteins and can be applied to a number of different systems.
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Affiliation(s)
- John E Gadbery
- Biochemistry and Structural Biology Graduate Program , Stony Brook University , Stony Brook , New York 11794-5215 , United States
| | - Nicole S Sampson
- Biochemistry and Structural Biology Graduate Program , Stony Brook University , Stony Brook , New York 11794-5215 , United States.,Department of Chemistry , Stony Brook University , Stony Brook , New York 11794-3400 , United States
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25
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Hines JP, Dent MR, Stevens DJ, Burstyn JN. Site-directed spin label electron paramagnetic resonance spectroscopy as a probe of conformational dynamics in the Fe(III) "locked-off" state of the CO-sensing transcription factor CooA. Protein Sci 2018; 27:1670-1679. [PMID: 30168206 PMCID: PMC6194275 DOI: 10.1002/pro.3449] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Revised: 05/25/2018] [Accepted: 05/29/2018] [Indexed: 01/30/2023]
Abstract
The transcriptional activator CooA belongs to the CRP/FNR (cAMP receptor protein/fumarate and nitrate reductase) superfamily of transcriptional regulators and uses heme to sense carbon monoxide (CO). Effector-driven allosteric activation is well understood in CRP, a CooA homologue. A structural allosteric activation model for CooA exists which parallels that of CRP; however, the role of protein dynamics, which is crucial in CRP, is not well understood in CooA. We employed site-directed spin labeling electron paramagnetic resonance spectroscopy to probe CooA motions on the μs-ms timescale. We created a series of Cys substitution variants, each with a cysteine residue introduced into a key functional region of the protein: K26C, E60C, F132C, D134C, and S175C. The heme environment and DNA binding affinity of each variant were comparable to those of wild-type CooA, with the exception of F132C, which displayed reduced DNA binding affinity. This observation confirms a previously hypothesized role for Phe132 in transmitting the allosteric CO binding signal. Osmolyte perturbation studies of Fe(III) "locked-off" CooA variants labeled with either MTSL or MAL-6 nitroxide spin labels revealed that multicomponent EPR spectra report on conformational flexibility on the μs-ms timescale. Multiple dynamic populations exist at every site examined in the structurally uncharacterized Fe(III) "locked-off" CooA. This observation suggests that, in direct contrast to effector-free CRP, Fe(III) "locked-off" CooA undergoes conformational exchange on the μs-ms timescale. Importantly, we establish MAL-6 as a spin label with a redox-stable linkage that may be utilized to compare conformational dynamics between functional states of CooA.
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Affiliation(s)
- Judy P. Hines
- Department of ChemistryUniversity of Wisconsin–MadisonMadisonWisconsin
| | - Matthew R. Dent
- Department of ChemistryUniversity of Wisconsin–MadisonMadisonWisconsin
| | - Daniel J. Stevens
- Department of ChemistryUniversity of Wisconsin–MadisonMadisonWisconsin
| | - Judith N. Burstyn
- Department of ChemistryUniversity of Wisconsin–MadisonMadisonWisconsin
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26
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Pan Y, Neupane S, Farmakes J, Oh M, Bentz K, Choi Y, Yang Z. Insights on the Structure, Molecular Weight and Activity of an Antibacterial Protein-Polymer Hybrid. Chemphyschem 2018; 19:651-658. [PMID: 29131929 PMCID: PMC6122959 DOI: 10.1002/cphc.201701097] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Indexed: 12/11/2022]
Abstract
Protein-polymer conjugates are attractive biomaterials which combine the functions of both proteins and polymers. The bioactivity of these hybrid materials, however, is often reduced upon conjugation. It is important to determine and monitor the protein structure and active site availability in order to optimize the polymer composition, attachment point, and abundance. The challenges in probing these insights are the large size and high complexity in the conjugates. Herein, we overcome the challenges by combining electron paramagnetic resonance (EPR) spectroscopy and atomic force microscopy (AFM) and characterize the structure of antibacterial hybrids formed by polyethylene glycol (PEG) and an antibacterial protein. We discovered that the primary reasons for activity loss were PEG blocking the substrate access pathway and/or altering protein surface charges. Our data indicated that the polymers tended to stay away from the protein surface and form a coiled conformation. The structural insights are meaningful for and applicable to the rational design of future hybrids.
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Affiliation(s)
- Yanxiong Pan
- Department of Chemistry and Biochemistry, North Dakota State University, 1231 Albrecht Blvd, Fargo, ND, 58108 (USA),
| | - Sunanda Neupane
- Department of Chemistry and Biochemistry, North Dakota State University, 1231 Albrecht Blvd, Fargo, ND, 58108 (USA),
| | - Jasmin Farmakes
- Department of Chemistry and Biochemistry, North Dakota State University, 1231 Albrecht Blvd, Fargo, ND, 58108 (USA),
| | - Myungkeun Oh
- Materials and Nanotechnology Program, North Dakota State University, 251 Batcheller Technology Center, Fargo, ND 58105
| | - Kylie Bentz
- Department of Chemistry and Biochemistry, North Dakota State University, 1231 Albrecht Blvd, Fargo, ND, 58108 (USA),
| | - Yongki Choi
- Materials and Nanotechnology Program, North Dakota State University, 251 Batcheller Technology Center, Fargo, ND 58105
- Department of Physics, North Dakota State University, 1211 Albrecht Blvd, Fargo, ND, 58108 (USA),
| | - Zhongyu Yang
- Department of Chemistry and Biochemistry, North Dakota State University, 1231 Albrecht Blvd, Fargo, ND, 58108 (USA),
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27
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The contribution of modern EPR to structural biology. Emerg Top Life Sci 2018; 2:9-18. [PMID: 33525779 PMCID: PMC7288997 DOI: 10.1042/etls20170143] [Citation(s) in RCA: 77] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Revised: 12/22/2017] [Accepted: 01/02/2018] [Indexed: 02/08/2023]
Abstract
Electron paramagnetic resonance (EPR) spectroscopy combined with site-directed spin labelling is applicable to biomolecules and their complexes irrespective of system size and in a broad range of environments. Neither short-range nor long-range order is required to obtain structural restraints on accessibility of sites to water or oxygen, on secondary structure, and on distances between sites. Many of the experiments characterize a static ensemble obtained by shock-freezing. Compared with characterizing the dynamic ensemble at ambient temperature, analysis is simplified and information loss due to overlapping timescales of measurement and system dynamics is avoided. The necessity for labelling leads to sparse restraint sets that require integration with data from other methodologies for building models. The double electron–electron resonance experiment provides distance distributions in the nanometre range that carry information not only on the mean conformation but also on the width of the native ensemble. The distribution widths are often inconsistent with Anfinsen's concept that a sequence encodes a single native conformation defined at atomic resolution under physiological conditions.
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28
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Ferraro NA, Cascio M. Cross-Linking-Mass Spectrometry Studies of Cholesterol Interactions with Human α1 Glycine Receptor. Anal Chem 2018; 90:2508-2516. [DOI: 10.1021/acs.analchem.7b03639] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Nicholas A. Ferraro
- Department of Chemistry and Biochemistry, Duquesne University, 600 Forbes Avenue, Pittsburgh, Pennsylvania 15282, United States
| | - Michael Cascio
- Department of Chemistry and Biochemistry, Duquesne University, 600 Forbes Avenue, Pittsburgh, Pennsylvania 15282, United States
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29
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M. Dunleavy K, Milshteyn E, Sorrentino Z, L. Pirman N, Liu Z, B. Chandler M, W. D’Amore P, E. Fanucci G. Spin-label scanning reveals conformational sensitivity of the bound helical interfaces of IA<sub>3</sub>. AIMS BIOPHYSICS 2018. [DOI: 10.3934/biophy.2018.3.166] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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30
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Sun J, Liu Z, Liu WG, Wu Y, Wang Y, Barnes JC, Hermann KR, Goddard WA, Wasielewski MR, Stoddart JF. Mechanical-Bond-Protected, Air-Stable Radicals. J Am Chem Soc 2017; 139:12704-12709. [DOI: 10.1021/jacs.7b06857] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
| | | | - Wei-Guang Liu
- Materials
and Process Simulation Center, California Institute of Technology, Pasadena, California 91125, United States
| | | | | | - Jonathan C. Barnes
- Department
of Chemistry, Washington University, One Brookings Drive, St. Louis, Missouri 63130, United States
| | | | - William A. Goddard
- Materials
and Process Simulation Center, California Institute of Technology, Pasadena, California 91125, United States
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31
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Meir A, Abdelhai A, Moskovitz Y, Ruthstein S. EPR Spectroscopy Targets Structural Changes in the E. coli Membrane Fusion CusB upon Cu(I) Binding. Biophys J 2017. [PMID: 28636907 DOI: 10.1016/j.bpj.2017.05.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Bacterial cells have developed sophisticated systems to deal with the toxicity of metal ions. Escherichia coli CusCFBA is a complex efflux system, responsible for transferring Cu(I) and Ag(I) ions; this system, located in the periplasm, involves four proteins, CusA, CusB, CusC, and CusF. CusA, CusB, and CusC are connected to one another in an oligomerization ratio of 3:6:3 CusA/CusB/CusC to form the CusCBA periplasm membrane transporter. CusB is an adaptor protein that connects the two membrane proteins CusA (inner membrane) and CusC (outer membrane). CusF is a metallochaperone that transfers Cu(I) and Ag(I) to the CusCBA transporter from the periplasm. The crystal structures of CusB, CusC, CusF, and the CusBA complex have been resolved, shedding some light on the efflux mechanism underlying this intriguing system. However, since CusB is an adaptor protein, its role in operating this system is significant, and should be understood in detail. Here, we utilize EPR spectroscopy to target the conformational changes that take place in the full CusB protein upon binding Cu(I). We reveal that CusB is a dimer in solution, and that the orientation of one molecule with respect to the other molecule changes upon Cu(I) coordination, resulting in a more compact CusB structure. These structural and topological changes upon Cu(I) binding probably play the role of a switch for opening the channel and transferring metal ions from CusB to CusC and out of the cell.
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Affiliation(s)
- Aviv Meir
- Department of Chemistry, Faculty of Exact Sciences, Bar Ilan University, Ramat-Gan, Israel
| | - Ahmad Abdelhai
- Department of Chemistry, Faculty of Exact Sciences, Bar Ilan University, Ramat-Gan, Israel
| | - Yoni Moskovitz
- Department of Chemistry, Faculty of Exact Sciences, Bar Ilan University, Ramat-Gan, Israel
| | - Sharon Ruthstein
- Department of Chemistry, Faculty of Exact Sciences, Bar Ilan University, Ramat-Gan, Israel.
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Palombo M, Bonucci A, Etienne E, Ciurli S, Uversky VN, Guigliarelli B, Belle V, Mileo E, Zambelli B. The relationship between folding and activity in UreG, an intrinsically disordered enzyme. Sci Rep 2017; 7:5977. [PMID: 28729736 PMCID: PMC5519622 DOI: 10.1038/s41598-017-06330-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Accepted: 06/12/2017] [Indexed: 12/02/2022] Open
Abstract
A growing body of literature on intrinsically disordered proteins (IDPs) led scientists to rethink the structure-function paradigm of protein folding. Enzymes are often considered an exception to the rule of intrinsic disorder (ID), believed to require a unique structure for catalysis. However, recent studies revealed the presence of disorder in several functional native enzymes. In the present work, we address the importance of dynamics for catalysis, by investigating the relationship between folding and activity in Sporosarcina pasteurii UreG (SpUreG), a P-loop GTPase and the first discovered native ID enzyme, involved in the maturation of the nickel-containing urease. The effect of denaturants and osmolytes on protein structure and activity was analyzed using circular dichroism (CD), Site-Directed Spin Labeling (SDSL) coupled to EPR spectroscopy, and enzymatic assays. Our data show that SpUreG needs a "flexibility window" to be catalytically competent, with both too low and too high mobility being detrimental for its activity.
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Affiliation(s)
- Marta Palombo
- Laboratory of Bioinorganic Chemistry, Department of Pharmacy and Biotechnology, University of Bologna, Viale G. Fanin 40, Bologna, 40127, Italy
| | - Alessio Bonucci
- Aix-Marseille Univ, CNRS, IMM (FR 3479), BIP (UMR 7281), 31 chemin Joseph Aiguier, Marseille, 13402, France
| | - Emilien Etienne
- Aix-Marseille Univ, CNRS, IMM (FR 3479), BIP (UMR 7281), 31 chemin Joseph Aiguier, Marseille, 13402, France
| | - Stefano Ciurli
- Laboratory of Bioinorganic Chemistry, Department of Pharmacy and Biotechnology, University of Bologna, Viale G. Fanin 40, Bologna, 40127, Italy
| | - Vladimir N Uversky
- Department of Molecular Medicine, University of South Florida, 12901 Bruce B. Downs Blvd., Tampa, MDC07, USA
| | - Bruno Guigliarelli
- Aix-Marseille Univ, CNRS, IMM (FR 3479), BIP (UMR 7281), 31 chemin Joseph Aiguier, Marseille, 13402, France
| | - Valérie Belle
- Aix-Marseille Univ, CNRS, IMM (FR 3479), BIP (UMR 7281), 31 chemin Joseph Aiguier, Marseille, 13402, France
| | - Elisabetta Mileo
- Aix-Marseille Univ, CNRS, IMM (FR 3479), BIP (UMR 7281), 31 chemin Joseph Aiguier, Marseille, 13402, France.
| | - Barbara Zambelli
- Laboratory of Bioinorganic Chemistry, Department of Pharmacy and Biotechnology, University of Bologna, Viale G. Fanin 40, Bologna, 40127, Italy.
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Levy AR, Turgeman M, Gevorkyan-Aiapetov L, Ruthstein S. The structural flexibility of the human copper chaperone Atox1: Insights from combined pulsed EPR studies and computations. Protein Sci 2017; 26:1609-1618. [PMID: 28543811 DOI: 10.1002/pro.3197] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Accepted: 05/15/2017] [Indexed: 01/20/2023]
Abstract
Metallochaperones are responsible for shuttling metal ions to target proteins. Thus, a metallochaperone's structure must be sufficiently flexible both to hold onto its ion while traversing the cytoplasm and to transfer the ion to or from a partner protein. Here, we sought to shed light on the structure of Atox1, a metallochaperone involved in the human copper regulation system. Atox1 shuttles copper ions from the main copper transporter, Ctr1, to the ATP7b transporter in the Golgi apparatus. Conventional biophysical tools such as X-ray or NMR cannot always target the various conformational states of metallochaperones, owing to a requirement for crystallography or low sensitivity and resolution. Electron paramagnetic resonance (EPR) spectroscopy has recently emerged as a powerful tool for resolving biological reactions and mechanisms in solution. When coupled with computational methods, EPR with site-directed spin labeling and nanoscale distance measurements can provide structural information on a protein or protein complex in solution. We use these methods to show that Atox1 can accommodate at least four different conformations in the apo state (unbound to copper), and two different conformations in the holo state (bound to copper). We also demonstrate that the structure of Atox1 in the holo form is more compact than in the apo form. Our data provide insight regarding the structural mechanisms through which Atox1 can fulfill its dual role of copper binding and transfer.
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Affiliation(s)
- Ariel R Levy
- The Department of Chemistry, Faculty of Exact Science, Bar Ilan University, Ramat-Gan, 5290002, Israel
| | - Meital Turgeman
- The Department of Chemistry, Faculty of Exact Science, Bar Ilan University, Ramat-Gan, 5290002, Israel
| | - Lada Gevorkyan-Aiapetov
- The Department of Chemistry, Faculty of Exact Science, Bar Ilan University, Ramat-Gan, 5290002, Israel
| | - Sharon Ruthstein
- The Department of Chemistry, Faculty of Exact Science, Bar Ilan University, Ramat-Gan, 5290002, Israel
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34
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Lawless MJ, Shimshi A, Cunningham TF, Kinde MN, Tang P, Saxena S. Analysis of Nitroxide-Based Distance Measurements in Cell Extracts and in Cells by Pulsed ESR Spectroscopy. Chemphyschem 2017; 18:1653-1660. [PMID: 28295910 DOI: 10.1002/cphc.201700115] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Indexed: 11/10/2022]
Abstract
Measurements of distances in cells by pulsed ESR spectroscopy afford tremendous opportunities to study proteins in native environments that are irreproducible in vitro. However, the in-cell environment is harsh towards the typical nitroxide radicals used in double electron-electron resonance (DEER) experiments. A systematic examination is performed on the loss of the DEER signal, including contributions from nitroxide decay and nitroxide side-chain cleavage. In addition, the possibility of extending the lifetime of the nitroxide radical by use of an oxidizing agent is investigated. Using this oxidizing agent, DEER distance measurements are performed on doubly nitroxide-labeled GB1, the immunoglobulin-binding domain of protein G, at varying incubation times in the cellular environment. It is found that, by comparison of the loss of DEER signal to the loss of the CW spectrum, cleavage of the nitroxide side chain contributes to the loss of DEER signal, which is significantly greater in cells than in cell extracts. Finally, local spin concentrations are monitored at varying incubation times to show the time required for molecular diffusion of a small globular protein within the cellular milieu.
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Affiliation(s)
- Matthew J Lawless
- Department of Chemistry, University of Pittsburgh, 219 Parkman Avenue, Pittsburgh, PA, 15260, USA
| | - Amit Shimshi
- Department of Chemistry, University of Pittsburgh, 219 Parkman Avenue, Pittsburgh, PA, 15260, USA
| | - Timothy F Cunningham
- Department of Chemistry, University of Pittsburgh, 219 Parkman Avenue, Pittsburgh, PA, 15260, USA.,Current address: Department of Chemistry, Hanover College, 484 Ball Dr, Hanover, IN, 47243, USA
| | - Monica N Kinde
- Department of Anesthesiology, University of Pittsburgh School of Medicine, 3501 5th Avenue, Pittsburgh, PA, 15213, USA.,Current address: Division of Basic Sciences, Kansas City University of Medicine and Biosciences, 2901 St. John's Blvd., Joplin, MO, 64804, USA
| | - Pei Tang
- Department of Anesthesiology, University of Pittsburgh School of Medicine, 3501 5th Avenue, Pittsburgh, PA, 15213, USA
| | - Sunil Saxena
- Department of Chemistry, University of Pittsburgh, 219 Parkman Avenue, Pittsburgh, PA, 15260, USA
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35
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Going Outside the TonB Box: Identification of Novel FepA-TonB Interactions In Vivo. J Bacteriol 2017; 199:JB.00649-16. [PMID: 28264993 DOI: 10.1128/jb.00649-16] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Accepted: 02/15/2017] [Indexed: 01/30/2023] Open
Abstract
In Gram-negative bacteria, the cytoplasmic membrane protein TonB transmits energy derived from proton motive force to energize transport of important nutrients through TonB-dependent transporters in the outer membrane. Each transporter consists of a beta barrel domain and a lumen-occluding cork domain containing an essential sequence called the TonB box. To date, the only identified site of transporter-TonB interaction is between the TonB box and residues ∼158 to 162 of TonB. While the mechanism of ligand transport is a mystery, a current model based on site-directed spin labeling and molecular dynamics simulations is that, following ligand binding, the otherwise-sequestered TonB box extends into the periplasm for recognition by TonB, which mediates transport by pulling or twisting the cork. In this study, we tested that hypothesis with the outer membrane transporter FepA using in vivo photo-cross-linking to explore interactions of its TonB box and determine whether additional FepA-TonB interaction sites exist. We found numerous specific sites of FepA interaction with TonB on the periplasmic face of the FepA cork in addition to the TonB box. Two residues, T32 and A33, might constitute a ligand-sensitive conformational switch. The facts that some interactions were enhanced in the absence of ligand and that other interactions did not require the TonB box argued against the current model and suggested that the transport process is more complex than originally conceived, with subtleties that might provide a mechanism for discrimination among ligand-loaded transporters. These results constitute the first study on the dynamics of TonB-gated transporter interaction with TonB in vivoIMPORTANCE The TonB system of Gram-negative bacteria has a noncanonical active transport mechanism involving signal transduction and proteins integral to both membranes. To achieve transport, the cytoplasmic membrane protein TonB physically contacts outer membrane transporters such as FepA. Only one contact between TonB and outer membrane transporters has been identified to date: the TonB box at the transporter amino terminus. The TonB box has low information content, raising the question of how TonB can discriminate among multiple different TonB-dependent transporters present in the bacterium if it is the only means of contact. Here we identified several additional sites through which FepA contacts TonB in vivo, including two neighboring residues that may explain how FepA signals to TonB that ligand has bound.
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Consentius P, Loll B, Gohlke U, Alings C, Müller C, Müller R, Teutloff C, Heinemann U, Kaupp M, Wahl MC, Risse T. Internal Dynamics of the 3-Pyrroline-N-Oxide Ring in Spin-Labeled Proteins. J Phys Chem Lett 2017; 8:1113-1117. [PMID: 28221042 DOI: 10.1021/acs.jpclett.6b02971] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Site-directed spin labeling is a versatile tool to study structure as well as dynamics of proteins using EPR spectroscopy. Methanethiosulfonate (MTS) spin labels tethered through a disulfide linkage to an engineered cysteine residue were used in a large number of studies to extract structural as well as dynamic information on the protein from the rotational dynamics of the nitroxide moiety. The ring itself was always considered to be a rigid body. In this contribution, we present a combination of high-resolution X-ray crystallography and EPR spectroscopy of spin-labeled protein single crystals demonstrating that the nitroxide ring inverts fast at ambient temperature while exhibiting nonplanar conformations at low temperature. We have used quantum chemical calculations to explore the potential energy that determines the ring dynamics as well as the impact of the geometry on the magnetic parameters probed by EPR spectroscopy.
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Affiliation(s)
- Philipp Consentius
- Institute of Chemistry and Biochemistry, Freie Universität Berlin , Takustraße 3, 14195 Berlin, Germany
| | - Bernhard Loll
- Institute of Chemistry and Biochemistry, Laboratory of Structural Biochemistry, Freie Universität Berlin , Takustraße 6, 14195 Berlin, Germany
| | - Ulrich Gohlke
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association , Robert-Rössle-Straße 10, 13125 Berlin, Germany
| | - Claudia Alings
- Institute of Chemistry and Biochemistry, Laboratory of Structural Biochemistry, Freie Universität Berlin , Takustraße 6, 14195 Berlin, Germany
| | - Carsten Müller
- Institute of Chemistry and Biochemistry, Freie Universität Berlin , Takustraße 3, 14195 Berlin, Germany
| | - Robert Müller
- Institute of Chemistry, Technische Universität Berlin , Sekr. C7, Straße des 17. Juni 135, 10623 Berlin, Germany
| | - Christian Teutloff
- Department of Physics, Freie Universität Berlin , Arnimallee 14, D-14195 Berlin, Germany
- Berlin Joint EPR Laboratory, Freie Universität Berlin , 14195 Berlin, Germany
| | - Udo Heinemann
- Institute of Chemistry and Biochemistry, Laboratory of Structural Biochemistry, Freie Universität Berlin , Takustraße 6, 14195 Berlin, Germany
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association , Robert-Rössle-Straße 10, 13125 Berlin, Germany
| | - Martin Kaupp
- Institute of Chemistry, Technische Universität Berlin , Sekr. C7, Straße des 17. Juni 135, 10623 Berlin, Germany
| | - Markus C Wahl
- Institute of Chemistry and Biochemistry, Laboratory of Structural Biochemistry, Freie Universität Berlin , Takustraße 6, 14195 Berlin, Germany
- Helmholtz-Zentrum Berlin für Materialien und Energie, Macromolecular Crystallography , Albert-Einstein-Straße 15, D-12489 Berlin, Germany
| | - Thomas Risse
- Institute of Chemistry and Biochemistry, Freie Universität Berlin , Takustraße 3, 14195 Berlin, Germany
- Berlin Joint EPR Laboratory, Freie Universität Berlin , 14195 Berlin, Germany
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37
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Pan Y, Neupane S, Farmakes J, Bridges M, Froberg J, Rao J, Qian SY, Liu G, Choi Y, Yang Z. Probing the structural basis and adsorption mechanism of an enzyme on nano-sized protein carriers. NANOSCALE 2017; 9:3512-3523. [PMID: 28244542 DOI: 10.1039/c7nr00276a] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Silica nanoparticles (SiNPs) are important nano-sized, solid-state carriers/hosts to load, store, and deliver biological or pharmaceutical cargoes. They are also good potential solid supports to immobilize proteins for fundamental protein structure and dynamics studies. However, precaution is necessary when using SiNPs in these areas because adsorption might alter the activity of the cargoes, especially when enzymes are loaded. Therefore, it becomes important to understand the structural basis of the cargo enzyme activity changes, if there is any. The high complexity and dynamics of the nano-bio interface present many challenges. Reported here is a comprehensive study of the structure, dynamics, and activity of a model enzyme, T4 lysozyme, upon adsorption to a few surface-modified SiNPs using several experimental techniques. Not surprisingly, a significant activity loss on each studied SiNP was found. The structural basis of the activity loss was identified based on results from a unique technique, the Electron Paramagnetic Resonance (EPR) spectroscopy, which probes structural information regardless of the complexity. Several docking models of the enzyme on SiNPs with different surfaces, at different enzyme-to-SiNP ratios are proposed. Interestingly, we found that the adsorbed enzyme can be desorbed via pH adjustment, which highlighted the potential to use SiNPs for enzyme/protein delivery or storage due to the high capacity. In order to use SiNPs as enzyme hosts, minimizing the enzymatic activity loss upon adsorption is needed. Lastly, the work outlined here demonstrate the use of EPR in probing structural information on the complex (inorganic)nano-bio interface.
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Affiliation(s)
- Yanxiong Pan
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND 58108, USA.
| | - Sunanda Neupane
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND 58108, USA.
| | - Jasmin Farmakes
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND 58108, USA.
| | - Michael Bridges
- Jules Stein Eye Institute, University of California, Los Angeles, CA 90025, USA
| | - James Froberg
- Department of Physics, North Dakota State University, Fargo, ND 58108, USA
| | - Jiajia Rao
- Department of Plant Sciences, North Dakota State University, Fargo, ND 58108, USA
| | - Steven Y Qian
- Department of Pharmaceutical Sciences, North Dakota State University, Fargo, ND 58108, USA
| | - Guodong Liu
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND 58108, USA.
| | - Yongki Choi
- Department of Physics, North Dakota State University, Fargo, ND 58108, USA
| | - Zhongyu Yang
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND 58108, USA.
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38
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Consentius P, Gohlke U, Loll B, Alings C, Heinemann U, Wahl MC, Risse T. Combining EPR spectroscopy and X-ray crystallography to elucidate the structure and dynamics of conformationally constrained spin labels in T4 lysozyme single crystals. Phys Chem Chem Phys 2017; 19:20723-20734. [DOI: 10.1039/c7cp03144k] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Unraveling structural and dynamic details of spin labeled proteins using a combination of single crystal EPR spectroscopy and X-ray crystallography.
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Affiliation(s)
- Philipp Consentius
- Freie Universität Berlin
- Institute of Chemistry and Biochemistry
- 14195 Berlin
- Germany
| | - Ulrich Gohlke
- Medicine in the Helmholtz Association
- 13125 Berlin
- Germany
| | - Bernhard Loll
- Freie Universität Berlin
- Institute of Chemistry and Biochemistry
- Laboratory of Structural Biochemistry
- 14195 Berlin
- Germany
| | - Claudia Alings
- Freie Universität Berlin
- Institute of Chemistry and Biochemistry
- Laboratory of Structural Biochemistry
- 14195 Berlin
- Germany
| | - Udo Heinemann
- Freie Universität Berlin
- Institute of Chemistry and Biochemistry
- 14195 Berlin
- Germany
- Medicine in the Helmholtz Association
| | - Markus C. Wahl
- Freie Universität Berlin
- Institute of Chemistry and Biochemistry
- Laboratory of Structural Biochemistry
- 14195 Berlin
- Germany
| | - Thomas Risse
- Freie Universität Berlin
- Institute of Chemistry and Biochemistry
- 14195 Berlin
- Germany
- Berlin Joint EPR Laboratory, Freie Universität Berlin
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39
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Consentius P, Gohlke U, Loll B, Alings C, Müller R, Heinemann U, Kaupp M, Wahl M, Risse T. Tracking Transient Conformational States of T4 Lysozyme at Room Temperature Combining X-ray Crystallography and Site-Directed Spin Labeling. J Am Chem Soc 2016; 138:12868-12875. [DOI: 10.1021/jacs.6b05507] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Philipp Consentius
- Institute
of Chemistry and Biochemistry, Freie Universität Berlin, Takustr. 3, 14195 Berlin, Germany
| | - Ulrich Gohlke
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Robert-Rössle-Str. 10, 13125 Berlin, Germany
| | - Bernhard Loll
- Institute
of Chemistry and Biochemistry, Freie Universität Berlin, Takustr. 6, 14195 Berlin, Germany
| | - Claudia Alings
- Institute
of Chemistry and Biochemistry, Freie Universität Berlin, Takustr. 6, 14195 Berlin, Germany
| | - Robert Müller
- Institute
of Chemistry, Sekr. C7, Technische Universität Berlin, Straße des
17. Juni 135, 10623 Berlin, Germany
| | - Udo Heinemann
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Robert-Rössle-Str. 10, 13125 Berlin, Germany
- Institute
of Chemistry and Biochemistry, Freie Universität Berlin, Takustr. 6, 14195 Berlin, Germany
| | - Martin Kaupp
- Institute
of Chemistry, Sekr. C7, Technische Universität Berlin, Straße des
17. Juni 135, 10623 Berlin, Germany
| | - Markus Wahl
- Institute
of Chemistry and Biochemistry, Freie Universität Berlin, Takustr. 6, 14195 Berlin, Germany
| | - Thomas Risse
- Institute
of Chemistry and Biochemistry, Freie Universität Berlin, Takustr. 3, 14195 Berlin, Germany
- Berlin
Joint EPR Laboratory, Freie Universität Berlin, Takustr. 3, 14195 Berlin, Germany
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40
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Gölz JP, NejatyJahromy Y, Bauer M, Muhammad A, Schnakenburg G, Grimme S, Schiemann O, Menche D. Design, Synthesis, EPR-Studies and Conformational Bias of Novel Spin-Labeled DCC-Analogues for the Highly Regioselective Labeling of Aliphatic and Aromatic Carboxylic Acids. Chemistry 2016; 22:9591-8. [PMID: 27272435 DOI: 10.1002/chem.201600528] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Indexed: 01/17/2023]
Abstract
Novel types of spin-labeled N,N'-dicyclohexylcarbodiimides (DCC) are reported that bear a 2,2,6,6-tetramethylpiperidinyloxyl (TEMPO) residue on one side and different aromatic and aliphatic cyclohexyl analogues on the other side of the diimide core. These readily available novel reagents add efficiently to aliphatic and aromatic carboxylic acids, forming two possible spin-labeled amide derivatives with different radical distances of the resulting amide. The addition of aromatic DCC analogues proceeds with excellent selectivity, giving amides where the carboxylic acid is exclusively connected to the aromatic residue, while little or no selectivity was observed for the aliphatic congeners. The usefulness of these adducts in structural studies was demonstrated by EPR (electron paramagnetic resonance) measurements of biradical adducts of biphenyl-4,4'-dicarboxylic acids. These analyses also reveal high degrees of conformational bias for aromatic DCC derivatives, which further underlines the powerfulness of these novel reagents. This observation was further corroborated by quantum chemical calculations, giving a detailed understanding of the structural dynamics, while detailed information on the solid state structure of all novel reagents was obtained by X-ray structure analyses.
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Affiliation(s)
- Jan Philipp Gölz
- Kekulé-Institut für Organische Chemie und Biochemie, Universität Bonn, Gerhard-Domagk-Str. 1, 53121, Bonn, Germany
| | - Yaser NejatyJahromy
- Institut für Physikalische und Theoretische Chemie, Universität Bonn, Wegelerstr. 12, 53115, Bonn, Germany
| | - Mirko Bauer
- Mulliken Center for Theoretical Chemistry, Institut für Physikalische und Theoretische Chemie, Universität Bonn, Beringstraße 4, 53115, Bonn, Germany
| | - Ashraf Muhammad
- Kekulé-Institut für Organische Chemie und Biochemie, Universität Bonn, Gerhard-Domagk-Str. 1, 53121, Bonn, Germany
| | - Gregor Schnakenburg
- Institut für Anorganische Chemie, Universität Bonn, Gerhard-Domagk-Straße 1, 53121, Bonn, Germany
| | - Stefan Grimme
- Mulliken Center for Theoretical Chemistry, Institut für Physikalische und Theoretische Chemie, Universität Bonn, Beringstraße 4, 53115, Bonn, Germany
| | - Olav Schiemann
- Institut für Physikalische und Theoretische Chemie, Universität Bonn, Wegelerstr. 12, 53115, Bonn, Germany
| | - Dirk Menche
- Kekulé-Institut für Organische Chemie und Biochemie, Universität Bonn, Gerhard-Domagk-Str. 1, 53121, Bonn, Germany.
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41
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Song L, Liu Z, Kaur P, Esquiaqui JM, Hunter RI, Hill S, Smith GM, Fanucci GE. Toward increased concentration sensitivity for continuous wave EPR investigations of spin-labeled biological macromolecules at high fields. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2016; 265:188-196. [PMID: 26923151 DOI: 10.1016/j.jmr.2016.02.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Revised: 02/09/2016] [Accepted: 02/10/2016] [Indexed: 06/05/2023]
Abstract
High-field, high-frequency electron paramagnetic resonance (EPR) spectroscopy at W-(∼94 GHz) and D-band (∼140 GHz) is important for investigating the conformational dynamics of flexible biological macromolecules because this frequency range has increased spectral sensitivity to nitroxide motion over the 100 ps to 2 ns regime. However, low concentration sensitivity remains a roadblock for studying aqueous samples at high magnetic fields. Here, we examine the sensitivity of a non-resonant thin-layer cylindrical sample holder, coupled to a quasi-optical induction-mode W-band EPR spectrometer (HiPER), for continuous wave (CW) EPR analyses of: (i) the aqueous nitroxide standard, TEMPO; (ii) the unstructured to α-helical transition of a model IDP protein; and (iii) the base-stacking transition in a kink-turn motif of a large 232 nt RNA. For sample volumes of ∼50 μL, concentration sensitivities of 2-20 μM were achieved, representing a ∼10-fold enhancement compared to a cylindrical TE011 resonator on a commercial Bruker W-band spectrometer. These results therefore highlight the sensitivity of the thin-layer sample holders employed in HiPER for spin-labeling studies of biological macromolecules at high fields, where applications can extend to other systems that are facilitated by the modest sample volumes and ease of sample loading and geometry.
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Affiliation(s)
- Likai Song
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310, USA
| | - Zhanglong Liu
- Department of Chemistry, University of Florida, PO Box 117200, Gainesville, FL 32611, USA
| | - Pavanjeet Kaur
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310, USA; Department of Physics, Florida State University, Tallahassee, FL 32306, USA
| | - Jackie M Esquiaqui
- Department of Chemistry, University of Florida, PO Box 117200, Gainesville, FL 32611, USA
| | - Robert I Hunter
- School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews KY16 9SS, United Kingdom
| | - Stephen Hill
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310, USA; Department of Physics, Florida State University, Tallahassee, FL 32306, USA
| | - Graham M Smith
- School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews KY16 9SS, United Kingdom
| | - Gail E Fanucci
- Department of Chemistry, University of Florida, PO Box 117200, Gainesville, FL 32611, USA.
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42
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Cunningham TF, Pornsuwan S, Horne WS, Saxena S. Rotameric preferences of a protein spin label at edge-strand β-sheet sites. Protein Sci 2016; 25:1049-60. [PMID: 26948069 DOI: 10.1002/pro.2918] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Revised: 03/01/2016] [Accepted: 03/03/2016] [Indexed: 12/20/2022]
Abstract
Protein spin labeling to yield the nitroxide-based R1 side chain is a powerful method to measure protein dynamics and structure by electron spin resonance. However, R1 measurements are complicated by the flexibility of the side chain. While analysis approaches for solvent-exposed α-helical environment have been developed to partially account for flexibility, similar work in β-sheets is lacking. The goal of this study is to provide the first essential steps for understanding the conformational preferences of R1 within edge β-strands using X-ray crystallography and double electron electron resonance (DEER) distance measurements. Crystal structures yielded seven rotamers for a non-hydrogen-bonded site and three rotamers for a hydrogen-bonded site. The observed rotamers indicate contextual differences in R1 conformational preferences compared to other solvent-exposed environments. For the DEER measurements, each strand site was paired with the same α-helical site elsewhere on the protein. The most probable distance observed by DEER is rationalized based on the rotamers observed in the crystal structure. Additionally, the appropriateness of common molecular modeling methods that account for R1 conformational preferences are assessed for the β-sheet environment. These results show that interpretation of R1 behavior in β-sheets is difficult and indicate further development is needed for these computational methods to correctly relate DEER distances to protein structure at edge β-strand sites.
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Affiliation(s)
- Timothy F Cunningham
- Department of Chemistry, University of Pittsburgh, 219 Parkman Ave, Pittsburgh, Pennsylvania, 15260
| | - Soraya Pornsuwan
- Department of Chemistry, University of Pittsburgh, 219 Parkman Ave, Pittsburgh, Pennsylvania, 15260
| | - W Seth Horne
- Department of Chemistry, University of Pittsburgh, 219 Parkman Ave, Pittsburgh, Pennsylvania, 15260
| | - Sunil Saxena
- Department of Chemistry, University of Pittsburgh, 219 Parkman Ave, Pittsburgh, Pennsylvania, 15260
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Joseph B, Sikora A, Cafiso DS. Ligand Induced Conformational Changes of a Membrane Transporter in E. coli Cells Observed with DEER/PELDOR. J Am Chem Soc 2016; 138:1844-7. [PMID: 26795032 PMCID: PMC4837646 DOI: 10.1021/jacs.5b13382] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
An unrealized goal in structural biology is the determination of structure and conformational change at high resolution for membrane proteins within the cellular environment. Pulsed electron-electron double resonance (PELDOR) is a well-established technique to follow conformational changes in purified membrane protein complexes. Here we demonstrate the first proof of concept for the use of PELDOR to observe conformational changes in a membrane protein in intact cells. We exploit the fact that outer membrane proteins usually lack reactive cysteines and that paramagnetic spin labels entering the periplasm are selectively reduced to achieve specific labeling of the cobalamin transporter BtuB in Escherichia coli. We characterize conformational changes in the second extracellular loop of BtuB upon ligand binding and compare the PELDOR data with high-resolution crystal structures. Our approach avoids detergent extraction, purification, and reconstitution usually required for these systems. With this approach, structure, function, conformational changes, and molecular interactions of outer membrane proteins can be studied at high resolution in the cellular environment.
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Affiliation(s)
- Benesh Joseph
- Institute of Physical and Theoretical Chemistry and Center for Biomolecular Magnetic Resonance, University of Frankfurt, Max-von-Laue-Strasse 7, 60438 Frankfurt am Main, Germany
| | - Arthur Sikora
- Department of Chemistry and Center for Membrane Biology, University of Virginia, McCormick Road, Charlottesville VA22904-4319, USA
| | - David S. Cafiso
- Department of Chemistry and Center for Membrane Biology, University of Virginia, McCormick Road, Charlottesville VA22904-4319, USA
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Gölz JP, Bockelmann S, Mayer K, Steinhoff HJ, Wieczorek H, Huss M, Klare JP, Menche D. EPR Studies of V-ATPase with Spin-Labeled Inhibitors DCC and Archazolid: Interaction Dynamics with Proton Translocating Subunit c. ChemMedChem 2015; 11:420-8. [DOI: 10.1002/cmdc.201500500] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Indexed: 01/16/2023]
Affiliation(s)
- Jan Philipp Gölz
- Kekulé-Institut für Organische Chemie und Biochemie; Rheinische Friedrich-Wilhelms-Universität Bonn; Gerhard-Domagk-Str. 1 53121 Bonn Germany
| | - Svenja Bockelmann
- Fachbereich Biologie/Chemie; Universität Osnabrück; 49069 Osnabrück Germany
| | - Kerstin Mayer
- Institut für Organische Chemie; Ruprecht-Karls-Universität Heidelberg; INF 270; 69120 Heidelberg Germany
| | | | - Helmut Wieczorek
- Fachbereich Biologie/Chemie; Universität Osnabrück; 49069 Osnabrück Germany
| | - Markus Huss
- Fachbereich Biologie/Chemie; Universität Osnabrück; 49069 Osnabrück Germany
| | - Johann P. Klare
- Fachbereich Physik; Universität Osnabrück; 49069 Osnabrück Germany
| | - Dirk Menche
- Kekulé-Institut für Organische Chemie und Biochemie; Rheinische Friedrich-Wilhelms-Universität Bonn; Gerhard-Domagk-Str. 1 53121 Bonn Germany
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Altenbach C, López CJ, Hideg K, Hubbell WL. Exploring Structure, Dynamics, and Topology of Nitroxide Spin-Labeled Proteins Using Continuous-Wave Electron Paramagnetic Resonance Spectroscopy. Methods Enzymol 2015; 564:59-100. [PMID: 26477248 DOI: 10.1016/bs.mie.2015.08.006] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Structural and dynamical characterization of proteins is of central importance in understanding the mechanisms underlying their biological functions. Site-directed spin labeling (SDSL) combined with continuous-wave electron paramagnetic resonance (CW EPR) spectroscopy has shown the capability of providing this information with site-specific resolution under physiological conditions for proteins of any degree of complexity, including those associated with membranes. This chapter introduces methods commonly employed for SDSL and describes selected CW EPR-based methods that can be applied to (1) map secondary and tertiary protein structure, (2) determine membrane protein topology, (3) measure protein backbone flexibility, and (4) reveal the existence of conformational exchange at equilibrium.
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Affiliation(s)
- Christian Altenbach
- Department of Chemistry and Biochemistry, Jules Stein Eye Institute, University of California, Los Angeles, California, USA
| | - Carlos J López
- Department of Chemistry and Biochemistry, Jules Stein Eye Institute, University of California, Los Angeles, California, USA
| | - Kálmán Hideg
- Institute of Organic and Medicinal Chemistry, University of Pécs, Pécs, Hungary
| | - Wayne L Hubbell
- Department of Chemistry and Biochemistry, Jules Stein Eye Institute, University of California, Los Angeles, California, USA.
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46
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Konov KB, Leonov DV, Isaev NP, Fedotov KY, Voronkova VK, Dzuba SA. Membrane–Sugar Interactions Probed by Pulsed Electron Paramagnetic Resonance of Spin Labels. J Phys Chem B 2015. [DOI: 10.1021/acs.jpcb.5b06864] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Konstantin B. Konov
- Zavoisky
Physical-Technical Institute, Russian Academy of Sciences, Kazan 420029, Russia
| | - Dmitry V. Leonov
- Institute
of Chemical Kinetics and Combustion, Russian Academy of Sciences, Novosibirsk 630090, Russia
- Novosibirsk State University, Novosibirsk, 630090, Russia
| | - Nikolay P. Isaev
- Institute
of Chemical Kinetics and Combustion, Russian Academy of Sciences, Novosibirsk 630090, Russia
- Novosibirsk State University, Novosibirsk, 630090, Russia
| | - Kirill Yu. Fedotov
- Institute
of Chemical Kinetics and Combustion, Russian Academy of Sciences, Novosibirsk 630090, Russia
- Novosibirsk State University, Novosibirsk, 630090, Russia
| | - Violeta K. Voronkova
- Zavoisky
Physical-Technical Institute, Russian Academy of Sciences, Kazan 420029, Russia
| | - Sergei A. Dzuba
- Institute
of Chemical Kinetics and Combustion, Russian Academy of Sciences, Novosibirsk 630090, Russia
- Novosibirsk State University, Novosibirsk, 630090, Russia
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47
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Evans EGB, Millhauser GL. Genetic Incorporation of the Unnatural Amino Acid p-Acetyl Phenylalanine into Proteins for Site-Directed Spin Labeling. Methods Enzymol 2015; 563:503-27. [PMID: 26478497 PMCID: PMC4841275 DOI: 10.1016/bs.mie.2015.06.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Site-directed spin labeling (SDSL) is a powerful tool for the characterization of protein structure and dynamics; however, its application in many systems is hampered by the reliance on unique and benign cysteine substitutions for the site-specific attachment of the spin label. An elegant solution to this problem involves the use of genetically encoded unnatural amino acids (UAAs) containing reactive functional groups that are chemically orthogonal to those of the 20 amino acids found naturally in proteins. These unique functional groups can then be selectively reacted with an appropriately functionalized spin probe. In this chapter, we detail the genetic incorporation of the ketone-bearing amino acid p-acetyl phenylalanine (pAcPhe) into recombinant proteins expressed in E. coli. Incorporation of pAcPhe is followed by chemoselective reaction of the ketone side chain with a hydroxylamine-functionalized nitroxide to afford the spin-labeled side chain "K1," and we present two protocols for successful K1 labeling of proteins bearing site-specific pAcPhe. We outline the basic requirements for pAcPhe incorporation and labeling, with an emphasis on practical aspects that must be considered by the researcher if high yields of UAA incorporation and efficient labeling reactions are to be achieved. To this end, we highlight recent advances that have led to increased yields of pAcPhe incorporation, and discuss the use of aniline-based catalysts allowing for facile conjugation of the hydroxylamine spin label under mild reaction conditions. To illustrate the utility of K1 labeling in proteins where traditional cysteine-based SDSL methods are problematic, we site-specifically K1 label the cellular prion protein at two positions in the C-terminal domain and determine the interspin distance using double electron-electron resonance EPR. Recent advances in UAA incorporation and ketone-based bioconjugation, in combination with the commercial availability of all requisite reagents, should make K1 labeling an increasingly viable alternative to cysteine-based methods for SDSL in proteins.
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Affiliation(s)
- Eric G B Evans
- Department of Chemistry and Biochemistry, University of California Santa Cruz, Santa Cruz, California, USA
| | - Glenn L Millhauser
- Department of Chemistry and Biochemistry, University of California Santa Cruz, Santa Cruz, California, USA.
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48
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Guzzi R, Bartucci R. Electron spin resonance of spin-labeled lipid assemblies and proteins. Arch Biochem Biophys 2015; 580:102-11. [PMID: 26116378 DOI: 10.1016/j.abb.2015.06.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Revised: 06/18/2015] [Accepted: 06/22/2015] [Indexed: 01/29/2023]
Abstract
Spin-label electron spin resonance (ESR) spectroscopy is a valuable means to study molecular mobility and interactions in biological systems. This paper deals with conventional, continuous wave ESR of nitroxide spin-labels at 9-GHz providing an introduction to the basic principles of the technique and applications to self-assembled lipid aggregates and proteins. Emphasis is given to segmental lipid chain order and rotational dynamics of lipid structures, environmental polarity of membranes and proteins, structure and conformational dynamics of proteins.
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Affiliation(s)
- Rita Guzzi
- Department of Physics, University of Calabria, 87036 Rende (CS), Italy
| | - Rosa Bartucci
- Department of Physics, University of Calabria, 87036 Rende (CS), Italy.
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Henrich E, Hein C, Dötsch V, Bernhard F. Membrane protein production in Escherichia coli cell-free lysates. FEBS Lett 2015; 589:1713-22. [PMID: 25937121 DOI: 10.1016/j.febslet.2015.04.045] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Revised: 04/17/2015] [Accepted: 04/21/2015] [Indexed: 01/01/2023]
Abstract
Cell-free protein production has become a core technology in the rapidly spreading field of synthetic biology. In particular the synthesis of membrane proteins, highly problematic proteins in conventional cellular production systems, is an ideal application for cell-free expression. A large variety of artificial as well as natural environments for the optimal co-translational folding and stabilization of membrane proteins can rationally be designed. The high success rate of cell-free membrane protein production allows to focus on individually selected targets and to modulate their functional and structural properties with appropriate supplements. The efficiency and robustness of lysates from Escherichia coli strains allow a wide diversity of applications and we summarize current strategies for the successful production of high quality membrane protein samples.
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Affiliation(s)
- Erik Henrich
- Institute of Biophysical Chemistry, Centre for Biomolecular Magnetic Resonance, J.W. Goethe-University, Frankfurt-am-Main, Germany
| | - Christopher Hein
- Institute of Biophysical Chemistry, Centre for Biomolecular Magnetic Resonance, J.W. Goethe-University, Frankfurt-am-Main, Germany
| | - Volker Dötsch
- Institute of Biophysical Chemistry, Centre for Biomolecular Magnetic Resonance, J.W. Goethe-University, Frankfurt-am-Main, Germany
| | - Frank Bernhard
- Institute of Biophysical Chemistry, Centre for Biomolecular Magnetic Resonance, J.W. Goethe-University, Frankfurt-am-Main, Germany.
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50
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Structure-relaxation mechanism for the response of T4 lysozyme cavity mutants to hydrostatic pressure. Proc Natl Acad Sci U S A 2015; 112:E2437-46. [PMID: 25918400 DOI: 10.1073/pnas.1506505112] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Application of hydrostatic pressure shifts protein conformational equilibria in a direction to reduce the volume of the system. A current view is that the volume reduction is dominated by elimination of voids or cavities in the protein interior via cavity hydration, although an alternative mechanism wherein cavities are filled with protein side chains resulting from a structure relaxation has been suggested [López CJ, Yang Z, Altenbach C, Hubbell WL (2013) Proc Natl Acad Sci USA 110(46):E4306-E4315]. In the present study, mechanisms for elimination of cavities under high pressure are investigated in the L99A cavity mutant of T4 lysozyme and derivatives thereof using site-directed spin labeling, pressure-resolved double electron-electron resonance, and high-pressure circular dichroism spectroscopy. In the L99A mutant, the ground state is in equilibrium with an excited state of only ∼ 3% of the population in which the cavity is filled by a protein side chain [Bouvignies et al. (2011) Nature 477(7362):111-114]. The results of the present study show that in L99A the native ground state is the dominant conformation to pressures of 3 kbar, with cavity hydration apparently taking place in the range of 2-3 kbar. However, in the presence of additional mutations that lower the free energy of the excited state, pressure strongly populates the excited state, thereby eliminating the cavity with a native side chain rather than solvent. Thus, both cavity hydration and structure relaxation are mechanisms for cavity elimination under pressure, and which is dominant is determined by details of the energy landscape.
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