1
|
Querci L, Grifagni D, Trindade IB, Silva JM, Louro RO, Cantini F, Piccioli M. Paramagnetic NMR to study iron sulfur proteins: 13C detected experiments illuminate the vicinity of the metal center. JOURNAL OF BIOMOLECULAR NMR 2023; 77:247-259. [PMID: 37853207 PMCID: PMC10687126 DOI: 10.1007/s10858-023-00425-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Accepted: 09/25/2023] [Indexed: 10/20/2023]
Abstract
The robustness of NMR coherence transfer in proximity of a paramagnetic center depends on the relaxation properties of the nuclei involved. In the case of Iron-Sulfur Proteins, different pulse schemes or different parameter sets often provide complementary results. Tailored versions of HCACO and CACO experiments significantly increase the number of observed Cα/C' connectivities in highly paramagnetic systems, by recovering many resonances that were lost due to paramagnetic relaxation. Optimized 13C direct detected experiments can significantly extend the available assignments, improving the overall knowledge of these systems. The different relaxation properties of Cα and C' nuclei are exploited in CACO vs COCA experiments and the complementarity of the two experiments is used to obtain structural information. The two [Fe2S2]+ clusters containing NEET protein CISD3 and the one [Fe4S4]2+ cluster containing HiPIP protein PioC have been taken as model systems. We show that tailored experiments contribute to decrease the blind sphere around the cluster, to extend resonance assignment of cluster bound cysteine residues and to retrieve details on the topology of the iron-bound ligand residues.
Collapse
Affiliation(s)
- Leonardo Querci
- Magnetic Resonance Center and Department of Chemistry, University of Florence, Via L. Sacconi 6, 50019, Sesto Fiorentino, Italy
| | - Deborah Grifagni
- Magnetic Resonance Center and Department of Chemistry, University of Florence, Via L. Sacconi 6, 50019, Sesto Fiorentino, Italy
| | - Inês B Trindade
- Instituto de Tecnologia Química e Biológica António Xavier (ITQB-NOVA), Universidade Nova de Lisboa, Av. da República (EAN), 2780-157, Oeiras, Portugal
- Division of Biology and Biological Engineering, California Institute of Technology, CA 91125, Pasadena, USA
| | - José Malanho Silva
- Magnetic Resonance Center and Department of Chemistry, University of Florence, Via L. Sacconi 6, 50019, Sesto Fiorentino, Italy
| | - Ricardo O Louro
- Instituto de Tecnologia Química e Biológica António Xavier (ITQB-NOVA), Universidade Nova de Lisboa, Av. da República (EAN), 2780-157, Oeiras, Portugal
| | - Francesca Cantini
- Magnetic Resonance Center and Department of Chemistry, University of Florence, Via L. Sacconi 6, 50019, Sesto Fiorentino, Italy
| | - Mario Piccioli
- Magnetic Resonance Center and Department of Chemistry, University of Florence, Via L. Sacconi 6, 50019, Sesto Fiorentino, Italy.
| |
Collapse
|
2
|
Valer L, Rossetto D, Scintilla S, Hu YJ, Tomar A, Nader S, Betinol IO, Mansy S. Methods to identify and characterize iron-sulfur oligopeptides in water. CAN J CHEM 2022. [DOI: 10.1139/cjc-2021-0237] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Iron-sulfur clusters are ubiquitous cofactors that mediate central biological processes. However, despite their long history, these metallocofactors remain challenging to investigate when coordinated to small (≤ six amino acids) oligopeptides in aqueous solution. In addition to being often unstable in vitro, iron-sulfur clusters can be found in a wide variety of forms with varied characteristics, which makes it difficult to easily discern what is in solution. This difficulty is compounded by the dynamics of iron-sulfur peptides, which frequently coordinate multiple types of clusters simultaneously. To aid investigations of such complex samples, a summary of data from multiple techniques used to characterize both iron-sulfur proteins and peptides is provided. Although not all spectroscopic techniques are equally insightful, it is possible to use several, readily available methods to gain insight into the complex composition of aqueous solutions of iron-sulfur peptides.
Collapse
Affiliation(s)
- Luca Valer
- University of Trento, 19034, Trento, Trentino-Alto Adige, Italy
| | | | | | - Yin Juan Hu
- University of Alberta, 3158, Chemistry, Edmonton, Alberta, Canada
| | - Anju Tomar
- University of Trento, 19034, Trento, Trentino-Alto Adige, Italy
| | - Serge Nader
- University of Alberta, 3158, Chemistry, Edmonton, Alberta, Canada
| | | | - Sheref Mansy
- University of Alberta, 3158, Chemistry, Edmonton, Alberta, Canada
| |
Collapse
|
3
|
Camponeschi F, Gallo A, Piccioli M, Banci L. The long-standing relationship between paramagnetic NMR and iron-sulfur proteins: the mitoNEET example. An old method for new stories or the other way around? MAGNETIC RESONANCE (GOTTINGEN, GERMANY) 2021; 2:203-221. [PMID: 37904758 PMCID: PMC10539769 DOI: 10.5194/mr-2-203-2021] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Accepted: 03/18/2021] [Indexed: 11/01/2023]
Abstract
Paramagnetic NMR spectroscopy and iron-sulfur (Fe-S) proteins have maintained a synergic relationship for decades. Indeed, the hyperfine shifts with their temperature dependencies and the relaxation rates of nuclei of cluster-bound residues have been extensively used as a fingerprint of the type and of the oxidation state of the Fe-S cluster within the protein frame. The identification of NMR signals from residues surrounding the metal cofactor is crucial for understanding the structure-function relationship in Fe-S proteins, but it is generally impaired in standard NMR experiments by paramagnetic relaxation enhancement due to the presence of the paramagnetic cluster(s). On the other hand, the availability of systems of different sizes and stabilities has, over the years, stimulated NMR spectroscopists to exploit iron-sulfur proteins as paradigmatic cases to develop experiments, models, and protocols. Here, the cluster-binding properties of human mitoNEET have been investigated by 1D and 2D 1 H diamagnetic and paramagnetic NMR, in its oxidized and reduced states. The NMR spectra of both oxidation states of mitoNEET appeared to be significantly different from those reported for previously investigated [ Fe 2 S 2 ] 2 + / + proteins. The protocol we have developed in this work conjugates spectroscopic information arising from "classical" paramagnetic NMR with an extended mapping of the signals of residues around the cluster which can be taken, even before the sequence-specific assignment is accomplished, as a fingerprint of the protein region constituting the functional site of the protein. We show how the combined use of 1D NOE experiments, 13 C direct-detected experiments, and double- and triple-resonance experiments tailored using R1 - and/or R2 -based filters significantly reduces the "blind" sphere of the protein around the paramagnetic cluster. This approach provided a detailed description of the unique electronic properties of mitoNEET, which are responsible for its biological function. Indeed, the NMR properties suggested that the specific electronic structure of the cluster possibly drives the functional properties of different [ Fe 2 S 2 ] proteins.
Collapse
Affiliation(s)
- Francesca Camponeschi
- Consorzio Interuniversitario Risonanze Magnetiche MetalloProteine,
Sesto Fiorentino, 50019, Italy
| | - Angelo Gallo
- Department of Pharmacy, University of Patras, Patras, 26504,
Greece
| | - Mario Piccioli
- Consorzio Interuniversitario Risonanze Magnetiche MetalloProteine,
Sesto Fiorentino, 50019, Italy
- Magnetic Resonance Center and Department of Chemistry, University of Florence, Sesto Fiorentino, 50019, Italy
| | - Lucia Banci
- Consorzio Interuniversitario Risonanze Magnetiche MetalloProteine,
Sesto Fiorentino, 50019, Italy
- Magnetic Resonance Center and Department of Chemistry, University of Florence, Sesto Fiorentino, 50019, Italy
| |
Collapse
|
4
|
Paramagnetic NMR Spectroscopy Is a Tool to Address Reactivity, Structure, and Protein–Protein Interactions of Metalloproteins: The Case of Iron–Sulfur Proteins. MAGNETOCHEMISTRY 2020. [DOI: 10.3390/magnetochemistry6040046] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The study of cellular machineries responsible for the iron–sulfur (Fe–S) cluster biogenesis has led to the identification of a large number of proteins, whose importance for life is documented by an increasing number of diseases linked to them. The labile nature of Fe–S clusters and the transient protein–protein interactions, occurring during the various steps of the maturation process, make their structural characterization in solution particularly difficult. Paramagnetic nuclear magnetic resonance (NMR) has been used for decades to characterize chemical composition, magnetic coupling, and the electronic structure of Fe–S clusters in proteins; it represents, therefore, a powerful tool to study the protein–protein interaction networks of proteins involving into iron–sulfur cluster biogenesis. The optimization of the various NMR experiments with respect to the hyperfine interaction will be summarized here in the form of a protocol; recently developed experiments for measuring longitudinal and transverse nuclear relaxation rates in highly paramagnetic systems will be also reviewed. Finally, we will address the use of extrinsic paramagnetic centers covalently bound to diamagnetic proteins, which contributed over the last twenty years to promote the applications of paramagnetic NMR well beyond the structural biology of metalloproteins.
Collapse
|
5
|
Banci L, Camponeschi F, Ciofi-Baffoni S, Piccioli M. The NMR contribution to protein-protein networking in Fe-S protein maturation. J Biol Inorg Chem 2018; 23:665-685. [PMID: 29569085 PMCID: PMC6006191 DOI: 10.1007/s00775-018-1552-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Accepted: 03/12/2018] [Indexed: 12/12/2022]
Abstract
Iron–sulfur proteins were among the first class of metalloproteins that were actively studied using NMR spectroscopy tailored to paramagnetic systems. The hyperfine shifts, their temperature dependencies and the relaxation rates of nuclei of cluster-bound residues are an efficient fingerprint of the nature and the oxidation state of the Fe–S cluster. NMR significantly contributed to the analysis of the magnetic coupling patterns and to the understanding of the electronic structure occurring in [2Fe–2S], [3Fe–4S] and [4Fe–4S] clusters bound to proteins. After the first NMR structure of a paramagnetic protein was obtained for the reduced E. halophila HiPIP I, many NMR structures were determined for several Fe–S proteins in different oxidation states. It was found that differences in chemical shifts, in patterns of unobserved residues, in internal mobility and in thermodynamic stability are suitable data to map subtle changes between the two different oxidation states of the protein. Recently, the interaction networks responsible for maturing human mitochondrial and cytosolic Fe–S proteins have been largely characterized by combining solution NMR standard experiments with those tailored to paramagnetic systems. We show here the contribution of solution NMR in providing a detailed molecular view of “Fe–S interactomics”. This contribution was particularly effective when protein–protein interactions are weak and transient, and thus difficult to be characterized at high resolution with other methodologies.
Collapse
Affiliation(s)
- Lucia Banci
- Magnetic Resonance Center CERM, University of Florence, Via Luigi Sacconi 6, Sesto Fiorentino, 50019, Florence, Italy. .,Department of Chemistry, University of Florence, Via della Lastruccia 3, Sesto Fiorentino, 50019, Florence, Italy.
| | - Francesca Camponeschi
- Magnetic Resonance Center CERM, University of Florence, Via Luigi Sacconi 6, Sesto Fiorentino, 50019, Florence, Italy.,Department of Chemistry, University of Florence, Via della Lastruccia 3, Sesto Fiorentino, 50019, Florence, Italy
| | - Simone Ciofi-Baffoni
- Magnetic Resonance Center CERM, University of Florence, Via Luigi Sacconi 6, Sesto Fiorentino, 50019, Florence, Italy.,Department of Chemistry, University of Florence, Via della Lastruccia 3, Sesto Fiorentino, 50019, Florence, Italy
| | - Mario Piccioli
- Magnetic Resonance Center CERM, University of Florence, Via Luigi Sacconi 6, Sesto Fiorentino, 50019, Florence, Italy. .,Department of Chemistry, University of Florence, Via della Lastruccia 3, Sesto Fiorentino, 50019, Florence, Italy.
| |
Collapse
|
6
|
Liu J, Chakraborty S, Hosseinzadeh P, Yu Y, Tian S, Petrik I, Bhagi A, Lu Y. Metalloproteins containing cytochrome, iron-sulfur, or copper redox centers. Chem Rev 2014; 114:4366-469. [PMID: 24758379 PMCID: PMC4002152 DOI: 10.1021/cr400479b] [Citation(s) in RCA: 540] [Impact Index Per Article: 54.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2013] [Indexed: 02/07/2023]
Affiliation(s)
- Jing Liu
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Saumen Chakraborty
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Parisa Hosseinzadeh
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Yang Yu
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Shiliang Tian
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Igor Petrik
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Ambika Bhagi
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Yi Lu
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| |
Collapse
|
7
|
Fleischhacker AS, Stubna A, Hsueh KL, Guo Y, Teter SJ, Rose JC, Brunold TC, Markley JL, Münck E, Kiley PJ. Characterization of the [2Fe-2S] cluster of Escherichia coli transcription factor IscR. Biochemistry 2012; 51:4453-62. [PMID: 22583201 DOI: 10.1021/bi3003204] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
IscR is an Fe-S cluster-containing transcription factor involved in a homeostatic mechanism that controls Fe-S cluster biogenesis in Escherichia coli. Although IscR has been proposed to act as a sensor of the cellular demands for Fe-S cluster biogenesis, the mechanism by which IscR performs this function is not known. In this study, we investigated the biochemical properties of the Fe-S cluster of IscR to gain insight into the proposed sensing activity. Mössbauer studies revealed that IscR contains predominantly a reduced [2Fe-2S](+) cluster in vivo. However, upon anaerobic isolation of IscR, some clusters became oxidized to the [2Fe-2S](2+) form. Cluster oxidation did not, however, alter the affinity of IscR for its binding site within the iscR promoter in vitro, indicating that the cluster oxidation state is not important for regulation of DNA binding. Furthermore, characterization of anaerobically isolated IscR using resonance Raman, Mössbauer, and nuclear magnetic resonance spectroscopies leads to the proposal that the [2Fe-2S] cluster does not have full cysteinyl ligation. Mutagenesis studies indicate that, in addition to the three previously identified cysteine residues (Cys92, Cys98, and Cys104), the highly conserved His107 residue is essential for cluster ligation. Thus, these data suggest that IscR binds the cluster with an atypical ligation scheme of three cysteines and one histidine, a feature that may be relevant to the proposed function of IscR as a sensor of cellular Fe-S cluster status.
Collapse
Affiliation(s)
- Angela S Fleischhacker
- Department of Biomolecular Chemistry, University of Wisconsin, Madison, Wisconsin 53706, United States
| | | | | | | | | | | | | | | | | | | |
Collapse
|
8
|
Offenbacher AR, Chen J, Barry BA. Perturbations of aromatic amino acids are associated with iron cluster assembly in ribonucleotide reductase. J Am Chem Soc 2011; 133:6978-88. [PMID: 21486062 DOI: 10.1021/ja107918g] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The β2 subunit of class Ia ribonucleotide reductases (RNR) contains an antiferromagnetically coupled μ-oxo bridged diiron cluster and a tyrosyl radical (Y122•). In this study, an ultraviolet resonance Raman (UVRR) difference technique describes the structural changes induced by the assembly of the iron cluster and by the reduction of the tyrosyl radical. Spectral contributions from aromatic amino acids are observed through UV resonance enhancement at 229 nm. Vibrational bands are assigned by comparison to histidine, phenylalanine, tyrosine, tryptophan, and 3-methylindole model compound data and by isotopic labeling of histidine in the β2 subunit. Reduction of the tyrosyl radical reveals Y122• Raman bands at 1499 and 1556 cm(-1) and Y122 Raman bands at 1170, 1199, and 1608 cm(-1). There is little perturbation of other aromatic amino acids when Y122• is reduced. Assembly of the iron cluster is shown to be accompanied by deprotonation of histidine. A p(2)H titration study supports the assignment of an elevated pK for the histidine. In addition, structural perturbations of tyrosine and tryptophan are detected. For tryptophan, comparison to model compound data suggests an increase in hydrogen bonding and a change in conformation when the iron cluster is removed. pH and (2)H(2)O studies imply that the perturbed tryptophan is in a low dielectric environment that is close to the metal center and protected from solvent exchange. Tyrosine contributions are attributed to a conformational or hydrogen-bonding change. In summary, our work shows that electrostatic and conformational perturbations of aromatic amino acids are associated with metal cluster assembly in RNR. These conformational changes may contribute to the allosteric effects, which regulate metal binding.
Collapse
Affiliation(s)
- Adam R Offenbacher
- Department of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
| | | | | |
Collapse
|
9
|
Westler WM, Lin IJ, Perczel A, Weinhold F, Markley JL. Hyperfine-shifted 13C resonance assignments in an iron-sulfur protein with quantum chemical verification: aliphatic C-H···S 3-center-4-electron interactions. J Am Chem Soc 2011; 133:1310-6. [PMID: 21207994 PMCID: PMC3033705 DOI: 10.1021/ja1049059] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
Although the majority of noncovalent interactions associated with hydrogen and heavy atoms in proteins and other biomolecules are classical hydrogen bonds between polar N−H or O−H moieties and O atoms or aromatic π electrons, high-resolution X-ray crystallographic models deposited in the Protein Data Bank show evidence for weaker C−H···O hydrogen bonds, including ones involving sp3-hybridized carbon atoms. Little evidence is available in proteins for the (even) weaker C−H···S interactions described in the crystallographic literature on small molecules. Here, we report experimental evidence and theoretical verification for the existence of nine aliphatic (sp3-hybridized) C−H···S 3-center−4-electron interactions in the protein Clostridium pasteurianum rubredoxin. Our evidence comes from the analysis of carbon-13 NMR chemical shifts assigned to atoms near the iron at the active site of this protein. We detected anomalous chemical shifts for these carbon-13 nuclei and explained their origin in terms of unpaired spin density from the iron atom being delocalized through interactions of the type: C−H···S−Fe, where S is the sulfur of one of the four cysteine side chains covalently bonded to the iron. These results suggest that polarized sulfur atoms in proteins can engage in multiple weak interactions with surrounding aliphatic groups. We analyze the strength and angular dependence of these interactions and conclude that they may contribute small, but significant, stabilization to the molecule.
Collapse
Affiliation(s)
- William M Westler
- National Magnetic Resonance Facility at Madison, University of Wisconsin, Madison, Wisconsin 53706, United States.
| | | | | | | | | |
Collapse
|
10
|
Iwasaki T, Samoilova RI, Kounosu A, Dikanov SA. Two-dimensional pulsed electron spin resonance characterization of 15N-labeled archaeal Rieske-type ferredoxin. FEBS Lett 2009; 583:3467-72. [PMID: 19804777 DOI: 10.1016/j.febslet.2009.09.050] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2009] [Revised: 09/24/2009] [Accepted: 09/29/2009] [Indexed: 11/25/2022]
Abstract
Two-dimensional electron spin-echo envelope modulation (ESEEM) analysis of the uniformly (15)N-labeled archaeal Rieske-type [2Fe-2S] ferredoxin (ARF) from Sulfolobus solfataricus P1 has been conducted in comparison with the previously characterized high-potential protein homologs. Major differences among these proteins were found in the hyperfine sublevel correlation (HYSCORE) lineshapes and intensities of the signals in the (++) quadrant, which are contributed from weakly coupled (non-coordinated) peptide nitrogens near the reduced clusters. They are less pronounced in the HYSCORE spectra of ARF than those of the high-potential protein homologs, and may account for the tuning of Rieske-type clusters in various redox systems.
Collapse
Affiliation(s)
- Toshio Iwasaki
- Department of Biochemistry and Molecular Biology, Nippon Medical School, Sendagi, Tokyo 113-8602, Japan.
| | | | | | | |
Collapse
|
11
|
Kolling DRJ, Samoilova RI, Shubin AA, Crofts AR, Dikanov SA. Proton environment of reduced Rieske iron-sulfur cluster probed by two-dimensional ESEEM spectroscopy. J Phys Chem A 2009; 113:653-67. [PMID: 19099453 PMCID: PMC2680161 DOI: 10.1021/jp806789x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The proton environment of the reduced [2Fe-2S] cluster in the water-soluble head domain of the Rieske iron-sulfur protein (ISF) from the cytochrome bc(1) complex of Rhodobacter sphaeroides has been studied by orientation-selected X-band 2D ESEEM. The 2D spectra show multiple cross-peaks from protons, with considerable overlap. Samples in which (1)H(2)O water was replaced by (2)H(2)O were used to determine which of the observed peaks belong to exchangeable protons, likely involved in hydrogen bonds in the neighborhood of the cluster. By correlating the cross-peaks from 2D spectra recorded at different parts of the EPR spectrum, lines from nine distinct proton signals were identified. Assignment of the proton signals was based on a point-dipole model for interaction with electrons of Fe(III) and Fe(II) ions, using the high-resolution structure of ISF from Rb. sphaeroides. Analysis of experimental and calculated tensors has led us to conclude that even 2D spectra do not completely resolve all contributions from nearby protons. Particularly, the seven resolved signals from nonexchangeable protons could be produced by at least 13 protons. The contributions from exchangeable protons were resolved by difference spectra ((1)H(2)O minus (2)H(2)O), and assigned to two groups of protons with distinct anisotropic hyperfine values. The largest measured coupling exceeded any calculated value. This discrepancy could result from limitations of the point dipole approximation in dealing with the distribution of spin density over the sulfur atoms of the cluster and the cysteine ligands, or from differences between the structure in solution and the crystallographic structure. The approach demonstrated here provides a paradigm for a wide range of studies in which hydrogen-bonding interactions with metallic centers has a crucial role in understanding the function.
Collapse
Affiliation(s)
- Derrick R. J. Kolling
- Center for Biophysics and Computational Biology, University of Illinois, Urbana, Illinois 61801
| | - Rimma I. Samoilova
- Institute of Chemical Kinetics and Combustion, Russian Academy of Sciences, Novosibirsk 630090, Russia
- Department of Biochemistry, University of Illinois, Urbana, Illinois 61801
| | - Alexander A. Shubin
- Boreskov Institute of Catalysis, Russian Academy of Sciences, Novosibirsk 6300090, Russia
| | - Antony R. Crofts
- Center for Biophysics and Computational Biology, University of Illinois, Urbana, Illinois 61801
- Department of Biochemistry, University of Illinois, Urbana, Illinois 61801
| | - Sergei A. Dikanov
- Department of Veterinary Clinical Medicine, University of Illinois, Urbana, Illinois 61801
| |
Collapse
|
12
|
Parales RE, Parales JV, Pelletier DA, Ditty JL. Diversity of microbial toluene degradation pathways. ADVANCES IN APPLIED MICROBIOLOGY 2008; 64:1-73, 2 p following 264. [PMID: 18485280 DOI: 10.1016/s0065-2164(08)00401-2] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Affiliation(s)
- R E Parales
- Department of Microbiology, University of California, Davis, California 95616, USA
| | | | | | | |
Collapse
|
13
|
Dikanov SA, Kolling DRJ, Endeward B, Samoilova RI, Prisner TF, Nair SK, Crofts AR. Identification of Hydrogen Bonds to the Rieske Cluster through the Weakly Coupled Nitrogens Detected by Electron Spin Echo Envelope Modulation Spectroscopy. J Biol Chem 2006; 281:27416-25. [PMID: 16854984 DOI: 10.1074/jbc.m604103200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The interaction of the reduced[2Fe-2S] cluster of isolated Rieske fragment from the bc1 complex of Rhodobacter sphaeroides with nitrogens (14N and 15N) from the local protein environment has been studied by X- and S-band pulsed EPR spectroscopy. The two-dimensional electron spin echo envelope modulation spectra of uniformly 15N-labeled protein show two well resolved cross-peaks with weak couplings of approximately 0.3-0.4 and 1.1 MHz in addition to couplings in the range of 6-8 MHz from two coordinating Ndelta of histidine ligands. The quadrupole coupling constants for weakly coupled nitrogens determined from S-band electron spin echo envelope modulation spectra identify them as Nepsilon of histidine ligands and peptide nitrogen (Np), respectively. Analysis of the line intensities in orientation-selected S-band spectra indicated that Np is the backbone N-atom of Leu-132 residue. The hyperfine couplings from Nepsilon and Np demonstrate the predominantly isotropic character resulting from the transfer of unpaired spin density onto the 2s orbitals of the nitrogens. Spectra also show that other peptide nitrogens in the protein environment must carry a 5-10 times smaller amount of spin density than the Np of Leu-132 residue. The appearance of the excess unpaired spin density on the Np of Leu-132 residue indicates its involvement in hydrogen bond formation with the bridging sulfur of the Rieske cluster. The configuration of the hydrogen bond therefore provides a preferred path for spin density transfer. Observation of similar splittings in the 15N spectra of other Rieske-type proteins and [2Fe-2S] ferredoxins suggests that a hydrogen bond between the bridging sulfur and peptide nitrogen is a common structural feature of [2Fe-2S] clusters.
Collapse
Affiliation(s)
- Sergei A Dikanov
- Department of Veterinary Clinical Medicine, University of Illinois, Urbana, Illinois 61801, USA
| | | | | | | | | | | | | |
Collapse
|
14
|
Balayssac S, Jiménez B, Piccioli M. Assignment strategy for fast relaxing signals: complete aminoacid identification in thulium substituted calbindin D 9K. JOURNAL OF BIOMOLECULAR NMR 2006; 34:63-73. [PMID: 16518694 DOI: 10.1007/s10858-005-5359-z] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2005] [Accepted: 11/14/2005] [Indexed: 05/07/2023]
Abstract
Paramagnetic proteins generally contain regions with diverse relaxation properties. Nuclei in regions far from the metal center may behave like those in diamagnetic proteins, but those closer to the metal experience rapid relaxation with accompanying line broadening. We have used a set of NMR experiments optimized to capture data from these various concentric regions in assigning the signals from a paramagnetic Calbindin D 9K derivative in which one of the two calcium ions has been replaced by thulium(III). Normal double- and triple-resonance experiments with 1H detection were used in collecting data from nuclei in the diamagnetic-like region; these approaches identified signals from fewer than 50% of the amino acid residues (those with d > 17.5 A from thulium(III)). Paramagnetism-optimized two-dimensional NMR experiments with 1H detection were used in collecting data from nuclei in the next nearer region (d > 15 A). Standard (d > 14 A) and optimized (d > 9 A) 13C direct-detection experiments were used to capture data from nuclei in the next layer. Finally nuclei closest to the metal were detected by one-dimensional 13C (d > 5 A) and one-dimensional 15N data collection (d > 4.2 A). NMR signals were assigned on the basis of through-bond correlations and, for signals closest to the metal, pseudocontact shifts. The latter were determined from chemical shift differences between assigned signals in thulium(III) and lanthanum(III) derivatives of Calbindin D 9K and they were interpreted on the basis of a structural model for the lanthanide-substituted protein. This approach yielded assignments of at least one resonance per amino acid residue, including those in the thulium(III) coordination sphere.
Collapse
Affiliation(s)
- Stéphane Balayssac
- Department of Chemistry, Magnetic Resonance Center (CERM), University of Florence, Via Luigi Sacconi 6, 50019, Sesto Fiorentino, Florence, Italy
| | | | | |
Collapse
|
15
|
Champreda V, Zhou NY, Leak DJ. Heterologous expression of alkene monooxygenase components fromXanthobacter autotrophicusPy2 and reconstitution of the active complex. FEMS Microbiol Lett 2004; 239:309-18. [PMID: 15476981 DOI: 10.1016/j.femsle.2004.09.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2004] [Revised: 05/25/2004] [Accepted: 09/07/2004] [Indexed: 11/24/2022] Open
Abstract
The coupling protein and ferredoxin from Xanthobacter autotrophicus Py2 alkene monooxygenase (Xamo) have been functionally expressed in both N-terminal affinity tagged fusion and native forms in Escherichia coli. However, attempts to express the NADH-oxidoreductase and oxygenase, always resulted in the production of inactive, insoluble proteins. Nevertheless, the recombinant reductase from the toluene 4-monooxygenase of Pseudomonas mendocina KR1 was found to functionally complement the Xamo system. In vitro reconstitution, using the recombinant coupling protein and other components purified from the wild type, showed that steady-state epoxidation rate and coupling efficiency were dependent on the relative concentration of Xamo components in the reaction. The optimal molar stoichiometric ratio of Xamo components was determined to be approximately 1:0.25-0.3:2:2 (oxygenase hexamer:reductase:ferredoxin:coupling protein), suggesting the formation of an efficient catalytic complex at the minimal stoichiometric ratio to saturate the probable two-fold symmetry binding sites on the oxygenase.
Collapse
Affiliation(s)
- Verawat Champreda
- Department of Biological Sciences, Imperial College London, London SW7 2AZ, UK
| | | | | |
Collapse
|
16
|
Skjeldal L, Peterson FC, Doreleijers JF, Moe LA, Pikus JD, Westler WM, Markley JL, Volkman BF, Fox BG. Solution structure of T4moC, the Rieske ferredoxin component of the toluene 4-monooxygenase complex. J Biol Inorg Chem 2004; 9:945-53. [PMID: 15452777 DOI: 10.1007/s00775-004-0594-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2004] [Accepted: 08/16/2004] [Indexed: 11/24/2022]
Abstract
Toluene 4-monooxygenase, a four-protein complex from Pseudomonas mendocina KR1, catalyzes the NADH- and O(2)-dependent hydroxylation of toluene to form p-cresol. The solution structure of the 112-amino-acid Rieske ferredoxin component, T4moC, was determined from 2D and 3D (1)H, (13)C, and (15)N NMR data. The structural model was refined through simulated annealing by molecular dynamics in torsion angle space with input from 1650 experimental restraints, including 1264 inter-proton distance restraints obtained from NOEs, 247 non-redundant intra-residue NOEs, 26 hydrogen bond restraints, and 113 dihedral angle ( phi, psi) restraints. The 20 calculated conformers that best satisfied the input restraints were submitted to refinement in explicit solvent to improve the stereochemical quality. With exclusion of ill-defined N- and C-terminal segments (Ser2; His111-Ser112) and residues near to the [2Fe-2S] cluster, the atomic root mean square deviation for the 20 conformers with respect to the mean coordinates was 1.09 A for the backbone and 1.60 A for all non-hydrogen atoms. The T4moC structure consists of 10 beta-strands arranged in the three anti-parallel beta-sheet topology observed in all Rieske [2Fe-2S] domain proteins. The S(gamma) of Cys45 and Cys64 and the N(delta1) of His47 and His67 provide the ligands to the [2Fe-2S] cluster of T4moC. (1)H-(15)N HSQC measurements show that both His47-N(epsilon2) and His67-N(epsilon2) are protonated at the pH of the NMR experiments. Comparisons are made between the present NMR structure, previous paramagnetic NMR studies of T4moC, and the X-ray structures of other members of the Rieske protein family.
Collapse
Affiliation(s)
- Lars Skjeldal
- IKB, Agricultural University of Norway, Box 5040, 1432 NLH, Norway
| | | | | | | | | | | | | | | | | |
Collapse
|
17
|
Dikanov SA, Shubin AA, Kounosu A, Iwasaki T, Samoilova RI. A comparative, two-dimensional 14N ESEEM characterization of reduced [2Fe-2S] clusters in hyperthermophilic archaeal high- and low-potential Rieske-type proteins. J Biol Inorg Chem 2004; 9:753-67. [PMID: 15243789 DOI: 10.1007/s00775-004-0571-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2003] [Accepted: 06/10/2004] [Indexed: 10/26/2022]
Abstract
Proteins of the Rieske and Rieske-type family contain a [2Fe-2S] cluster with mixed ligation by two histidines and two cysteines, and play important roles in various biological electron transfer reactions. We report here the comparative orientation-selected ESEEM and HYSCORE studies of the reduced clusters from two hyperthermophilic Rieske-type proteins; a high-potential, archaeal Rieske protein called sulredoxin (SDX) from Sulfolobus tokodaii with weak homology to the cytochrome bc-associated Rieske proteins, and a low-potential, archaeal homolog of an oxygenase-associated Rieske-type ferredoxin (ARF) from Sulfolobus solfataricus. (14)N ESEEM and HYSCORE spectra of SDX and ARF show well-defined variations, which are primarily determined by changes of quadrupole couplings (up to 50% depending on the selected orientation) of the two coordinated nitrogens. These are due to variations in coordination geometry of the histidine imidazole ligands rather than to variations of hyperfine couplings of these nitrogens, which do not exceed 8-10%. The measured quadrupole couplings and their differences in the two proteins are consistent with those calculated using the reported crystal structures of high- and low-potential Rieske proteins. These results suggest that exploration of quadrupole tensors might provide a more accurate method for characterization of the histidine coordination in different proteins and mutants than hyperfine tensors, and might have potential applications in a wider range of biological systems.
Collapse
Affiliation(s)
- Sergei A Dikanov
- Department of Veterinary Clinical Medicine, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
| | | | | | | | | |
Collapse
|
18
|
Conrads TP, Issaq HJ, Hoang VM. Current strategies for quantitative proteomics. ADVANCES IN PROTEIN CHEMISTRY 2004; 65:133-59. [PMID: 12964368 DOI: 10.1016/s0065-3233(03)01018-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/28/2023]
Affiliation(s)
- Thomas P Conrads
- Biomedical Proteomics Program, SAIC-Frederick, National Cancer Institute at Frederick, Frederick, Maryland 21702, USA
| | | | | |
Collapse
|
19
|
Kounosu A, Li Z, Cosper NJ, Shokes JE, Scott RA, Imai T, Urushiyama A, Iwasaki T. Engineering a three-cysteine, one-histidine ligand environment into a new hyperthermophilic archaeal Rieske-type [2Fe-2S] ferredoxin from Sulfolobus solfataricus. J Biol Chem 2004; 279:12519-28. [PMID: 14726526 DOI: 10.1074/jbc.m305923200] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We heterologously overproduced a hyperthermostable archaeal low potential (E(m) = -62 mV) Rieske-type ferredoxin (ARF) from Sulfolobus solfataricus strain P-1 and its variants in Escherichia coli to examine the influence of ligand substitutions on the properties of the [2Fe-2S] cluster. While two cysteine ligand residues (Cys(42) and Cys(61)) are essential for the cluster assembly and/or stability, the contributions of the two histidine ligands to the cluster assembly in the archaeal Rieske-type ferredoxin appear to be inequivalent as indicated by much higher stability of the His(64) --> Cys variant (H64C) than the His(44) --> Cys variant (H44C). The x-ray absorption and resonance Raman spectra of the H64C variant firmly established the formation of a novel, oxidized [2Fe-2S] cluster with one histidine and three cysteine ligands in the archaeal Rieske-type protein moiety. Comparative resonance Raman features of the wild-type, natural abundance and uniformly (15)N-labeled ARF and its H64C variant showed significant mixing of the Fe-S and Fe-N stretching characters for an oxidized biological [2Fe-2S] cluster with partial histidine ligation.
Collapse
Affiliation(s)
- Asako Kounosu
- Department of Biochemistry and Molecular Biology, Nippon Medical School, Sendagi, Bunkyo-ku, Tokyo 113-8602, Japan
| | | | | | | | | | | | | | | |
Collapse
|
20
|
Abstract
Based on structural, biochemical, and genetic data, the soluble diiron monooxygenases can be divided into four groups: the soluble methane monooxygenases, the Amo alkene monooxygenase of Rhodococcus corallinus B-276, the phenol hydroxylases, and the four-component alkene/aromatic monooxygenases. The limited phylogenetic distribution of these enzymes among bacteria, together with available genetic evidence, indicates that they have been spread largely through horizontal gene transfer. Phylogenetic analyses reveal that the alpha- and beta-oxygenase subunits are paralogous proteins and were derived from an ancient gene duplication of a carboxylate-bridged diiron protein, with subsequent divergence yielding a catalytic alpha-oxygenase subunit and a structural beta-oxygenase subunit. The oxidoreductase and ferredoxin components of these enzymes are likely to have been acquired by horizontal transfer from ancestors common to unrelated diiron and Rieske center oxygenases and other enzymes. The cumulative results of phylogenetic reconstructions suggest that the alkene/aromatic monooxygenases diverged first from the last common ancestor for these enzymes, followed by the phenol hydroxylases, Amo alkene monooxygenase, and methane monooxygenases.
Collapse
Affiliation(s)
- Joseph G Leahy
- Department of Biological Sciences, University of Alabama in Huntsville, Huntsville, AL 35899, USA.
| | | | | |
Collapse
|
21
|
Cafaro V, Scognamiglio R, Viggiani A, Izzo V, Passaro I, Notomista E, Piaz FD, Amoresano A, Casbarra A, Pucci P, Di Donato A. Expression and purification of the recombinant subunits of toluene/o-xylene monooxygenase and reconstitution of the active complex. EUROPEAN JOURNAL OF BIOCHEMISTRY 2002; 269:5689-99. [PMID: 12423369 DOI: 10.1046/j.1432-1033.2002.03281.x] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
This paper describes the cloning of the genes coding for each component of the complex of toluene/o-xylene monooxygenase from Pseudomonas stutzeri OX1, their expression, purification and characterization. Moreover, the reconstitution of the active complex from the recombinant subunits has been obtained, and the functional role of each component in the electron transfer from the electron donor to molecular oxygen has been determined. The coexpression of subunits B, E and A leads to the formation of a subcomplex, named H, with a quaternary structure (BEA)2, endowed with hydroxylase activity. Tomo F component is an NADH oxidoreductase. The purified enzyme contains about 1 mol of FAD, 2 mol of iron, and 2 mol of acid labile sulfide per mol of protein, as expected for the presence of one [2Fe-2S] cluster, and exhibits a typical flavodoxin absorption spectrum. Interestingly, the sequence of the protein does not correspond to that previously predicted on the basis of DNA sequence. We have shown that this depends on minor errors in the gene sequence that we have corrected. C component is a Rieske-type ferredoxin, whose iron and acid labile sulfide content is in agreement with the presence of one [2Fe-2S] cluster. The cluster is very sensitive to oxygen damage. Mixtures of the subcomplex H and of the subunits F, C and D are able to oxidize p-cresol into 4-methylcathecol, thus demonstrating the full functionality of the recombinant subunits as purified. Finally, experimental evidence is reported which strongly support a model for the electron transfer. Subunit F is the first member of an electron transport chain which transfers electrons from NADH to C, which tunnels them to H subcomplex, and eventually to molecular oxygen.
Collapse
Affiliation(s)
- Valeria Cafaro
- Dipartimento di Chimica Biologica and Dipartimento di Chimica Organica e Biochimica, Università di Napoli Federico II, Italy
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
22
|
Kahng HY, Malinverni JC, Majko MM, Kukor JJ. Genetic and functional analysis of the tbc operons for catabolism of alkyl- and chloroaromatic compounds in Burkholderia sp. strain JS150. Appl Environ Microbiol 2001; 67:4805-16. [PMID: 11571188 PMCID: PMC93235 DOI: 10.1128/aem.67.10.4805-4816.2001] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Burkholderia sp. strain JS150 is able to metabolize a wide range of alkyl-and chloroaromatic hydrocarbons through multiple, apparently redundant catabolic pathways. Previous research has shown that strain JS150 is able to synthesize enzymes for multiple upper pathways as well as multiple lower pathways to accommodate variously substituted catechols that result from degradation of complex mixtures of monoaromatic compounds. We report here the genetic organization and functional characterization of a gene cluster, designated tbc (for toluene, benzene, and chlorobenzene utilization), which has been cloned as a 14.3-kb DNA fragment from strain JS150 into vector pRO1727. The cloned DNA fragment expressed in Pseudomonas aeruginosa PAO1c allowed the recombinant to grow on toluene or benzene and to transform chlorobenzene, trichloroethylene, phenol, and cresols. The tbc genes are organized into two divergently transcribed operons, tbc1 and tbc2, each comprised of six open reading frames. Similarity searches of databases revealed that the tbc1 and tbc2 genes showed significant homology to multicomponent cresol and phenol hydroxylases and to toluene and benzene monooxygenases, respectively. Deletion mutagenesis and product analysis were used to demonstrate that tbc2 plays a role in the initial catabolism of the unactivated alkyl- or chloroaromatic substrate and that the tbc1 gene products play a role in the catabolism of the first metabolite that results from transformation of the initial substrate. Phylogenetic analysis was used to compare individual components of these tbc monooxygenases with similar sequences in the databases. These results provide further evidence for the existence of multiple, functionally redundant alkyl- and chloroaromatic monooxygenases in strain JS150.
Collapse
Affiliation(s)
- H Y Kahng
- Biotechnology Center for Agriculture and the Environment, Rutgers University, New Brunswick, New Jersey 08901-8520, USA
| | | | | | | |
Collapse
|
23
|
Studts JM, Mitchell KH, Pikus JD, McClay K, Steffan RJ, Fox BG. Optimized expression and purification of toluene 4-monooxygenase hydroxylase. Protein Expr Purif 2000; 20:58-65. [PMID: 11035951 DOI: 10.1006/prep.2000.1281] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Toluene 4-monooxygenase is a four-protein complex that catalyzes the O(2)- and NADH-dependent oxidation of toluene to p-cresol. The influence of various expression systems on the host cell growth characteristics, purified protein yields, and specific activity of the hydroxylase (T4moH) component of the complex was evaluated by considering the cell mass obtained per liter of fermentation culture medium, the purified protein obtained per gram of cell mass, and the specific activity of purified T4moH. The specific activity of purified T4moH was determined to be 1200-1250 nmol of p-cresol formed per minute per milligram of T4moH in air-saturated 50 mM phosphate buffer, pH 7.5, at 25 degrees C in the presence of optimal concentrations of the other protein components of the complex, saturating toluene (5.8 mM at 25 degrees C), and saturating NADH (1 mM). This value was obtained for T4moH purified from several different expression systems and apparently represents the maximal specific activity of the enzyme complex for toluene hydroxylation. By manipulation of vectors and gene inserts to eliminate adventitious catalytic turnover of NADH, up to 60-fold increase in the volumetric yield of T4moH activity was obtained from recombinant fermentations in Escherichia coli BL21(DE3).
Collapse
Affiliation(s)
- J M Studts
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53705, USA
| | | | | | | | | | | |
Collapse
|
24
|
Xia B, Jenk D, LeMaster DM, Westler WM, Markley JL. Electron-nuclear interactions in two prototypical [2Fe-2S] proteins: selective (chiral) deuteration and analysis of (1)H and (2)H NMR signals from the alpha and beta hydrogens of cysteinyl residues that ligate the iron in the active sites of human ferredoxin and Anabaena 7120 vegetative ferredoxin. Arch Biochem Biophys 2000; 373:328-34. [PMID: 10620356 DOI: 10.1006/abbi.1999.1576] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A vertebrate ferredoxin (human ferredoxin) and a plant-type ferredoxin (the ferredoxin from the vegetative form of Anabaena 7120) were labeled selectively with deuterium at their active site cysteines. The recombinant proteins were produced in Escherichia coli and labeled by replacing natural abundance cysteine in the defined culture medium with (2)H(alpha)-cysteine, (2)H(beta2), (2)H(beta3)-cysteine, or (2)H(beta2)-cystine. The chiral labeled cystine ((2)H(beta2)-cystine) was prepared by selective hydrogen exchange catalyzed by cystathionine gamma-synthase. NMR spectra of these samples in their oxidized and reduced states support unambiguous identifications by atom type of (1)H and (2)H NMR signals from the cysteine alpha and beta hydrogens. These signals lie outside the normal diamagnetic spectral region as a result of interaction of the hydrogens with unpaired electron density from the iron-sulfur cluster, and their chemical shifts are highly dependent on local conformation at the active site. The very different chemical properties of the iron centers of plant-type and vertebrate ferredoxins reflect relatively small differences in the conformation of the iron-sulfur cluster ligands.
Collapse
Affiliation(s)
- B Xia
- Graduate Program in Biophysics, Department of Biochemistry, National Magnetic Resonance Facility at Madison, University of Wisconsin-Madison, 420 Henry Mall, Madison, Wisconsin 53706, USA
| | | | | | | | | |
Collapse
|
25
|
Veenstra TD, Martinović S, Anderson GA, Pasa-Tolić L, Smith RD. Proteome analysis using selective incorporation of isotopically labeled amino acids. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2000; 11:78-82. [PMID: 10631667 DOI: 10.1016/s1044-0305(99)00120-8] [Citation(s) in RCA: 113] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
A method is described for identifying intact proteins from genomic databases using a combination of accurate molecular mass measurements and partial amino acid content. An initial demonstration was conducted for proteins isolated from Escherichia coli (E. coli) using a multiple auxotrophic strain of K12. Proteins extracted from the organism grown in natural isotopic abundance minimal medium and also minimal medium containing isotopically labeled leucine (Leu-D10), were mixed and analyzed by capillary isoelectric focusing (CIEF) coupled with Fourier transform ion cyclotron resonance mass spectrometry (FTICR). The incorporation of the isotopically labeled Leu residue has no effect on the CIEF separation of the protein, therefore both versions of the protein are observed within the same FTICR spectrum. The difference in the molecular mass of the natural isotopic abundance and Leu-D10 isotopically labeled proteins is used to determine the number of Leu residues present in that particular protein. Knowledge of the molecular mass and number of Leu residues present can be used to unambiguously identify the intact protein. Preliminary results show the efficacy of this method for unambiguously identifying proteins isolated from E. coli.
Collapse
Affiliation(s)
- T D Veenstra
- Environmental and Molecular Sciences Laboratory, Pacific Northwest National Laboratories, Richland, Washington 99352, USA
| | | | | | | | | |
Collapse
|
26
|
|