51
|
Lee MD, Dennis ML, Swarbrick JD, Graham B. Enantiomeric two-armed lanthanide-binding tags for complementary effects in paramagnetic NMR spectroscopy. Chem Commun (Camb) 2016; 52:7954-7. [DOI: 10.1039/c6cc02325h] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
A new pair of two-armed lanthanide-binding tags provide distinct sets of structural restraints when attached to the same site of a protein.
Collapse
Affiliation(s)
- Michael D. Lee
- Monash Institute of Pharmaceutical Sciences
- Monash University
- Parkville
- Australia
| | - Matthew L. Dennis
- Monash Institute of Pharmaceutical Sciences
- Monash University
- Parkville
- Australia
- CSIRO Biosciences Program
| | - James D. Swarbrick
- Monash Institute of Pharmaceutical Sciences
- Monash University
- Parkville
- Australia
| | - Bim Graham
- Monash Institute of Pharmaceutical Sciences
- Monash University
- Parkville
- Australia
| |
Collapse
|
52
|
Pseudocontact Shift-Driven Iterative Resampling for 3D Structure Determinations of Large Proteins. J Mol Biol 2016; 428:522-32. [DOI: 10.1016/j.jmb.2016.01.007] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Revised: 01/08/2016] [Accepted: 01/08/2016] [Indexed: 01/23/2023]
|
53
|
Swarbrick JD, Ung P, Dennis ML, Lee MD, Chhabra S, Graham B. Installation of a Rigid EDTA-Like Motif into a Protein α-Helix for Paramagnetic NMR Spectroscopy with Cobalt(II) Ions. Chemistry 2015; 22:1228-32. [DOI: 10.1002/chem.201503139] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2015] [Revised: 12/02/2015] [Indexed: 11/06/2022]
Affiliation(s)
- James D. Swarbrick
- Monash Institute of Pharmaceutical Sciences; Monash University; 381 Royal Parade Parkville 3052 Victoria Australia
| | - Phuc Ung
- Monash Institute of Pharmaceutical Sciences; Monash University; 381 Royal Parade Parkville 3052 Victoria Australia
| | - Matthew L. Dennis
- Monash Institute of Pharmaceutical Sciences; Monash University; 381 Royal Parade Parkville 3052 Victoria Australia
| | - Michael D. Lee
- Monash Institute of Pharmaceutical Sciences; Monash University; 381 Royal Parade Parkville 3052 Victoria Australia
| | - Sandeep Chhabra
- Monash Institute of Pharmaceutical Sciences; Monash University; 381 Royal Parade Parkville 3052 Victoria Australia
| | - Bim Graham
- Monash Institute of Pharmaceutical Sciences; Monash University; 381 Royal Parade Parkville 3052 Victoria Australia
| |
Collapse
|
54
|
Andrałojć W, Berlin K, Fushman D, Luchinat C, Parigi G, Ravera E, Sgheri L. Information content of long-range NMR data for the characterization of conformational heterogeneity. JOURNAL OF BIOMOLECULAR NMR 2015; 62:353-71. [PMID: 26044033 PMCID: PMC4782772 DOI: 10.1007/s10858-015-9951-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Accepted: 05/25/2015] [Indexed: 05/16/2023]
Abstract
Long-range NMR data, namely residual dipolar couplings (RDCs) from external alignment and paramagnetic data, are becoming increasingly popular for the characterization of conformational heterogeneity of multidomain biomacromolecules and protein complexes. The question addressed here is how much information is contained in these averaged data. We have analyzed and compared the information content of conformationally averaged RDCs caused by steric alignment and of both RDCs and pseudocontact shifts caused by paramagnetic alignment, and found that, despite the substantial differences, they contain a similar amount of information. Furthermore, using several synthetic tests we find that both sets of data are equally good towards recovering the major state(s) in conformational distributions.
Collapse
Affiliation(s)
- Witold Andrałojć
- Center for Magnetic Resonance (CERM), University of Florence, Via
L. Sacconi 6, 50019, Sesto Fiorentino, Italy
| | - Konstantin Berlin
- Department of Chemistry and Biochemistry, Center for Biomolecular
Structure and Organization, University of Maryland, College Park, MD 20742, USA
| | - David Fushman
- Department of Chemistry and Biochemistry, Center for Biomolecular
Structure and Organization, University of Maryland, College Park, MD 20742, USA
- Corresponding authors: David Fushman, ,
Claudio Luchinat,
| | - Claudio Luchinat
- Center for Magnetic Resonance (CERM), University of Florence, Via
L. Sacconi 6, 50019, Sesto Fiorentino, Italy
- Department of Chemistry "Ugo Schiff", University
of Florence, Via della Lastruccia 3, 50019, Sesto Fiorentino, Italy
- Corresponding authors: David Fushman, ,
Claudio Luchinat,
| | - Giacomo Parigi
- Center for Magnetic Resonance (CERM), University of Florence, Via
L. Sacconi 6, 50019, Sesto Fiorentino, Italy
- Department of Chemistry "Ugo Schiff", University
of Florence, Via della Lastruccia 3, 50019, Sesto Fiorentino, Italy
| | - Enrico Ravera
- Center for Magnetic Resonance (CERM), University of Florence, Via
L. Sacconi 6, 50019, Sesto Fiorentino, Italy
- Department of Chemistry "Ugo Schiff", University
of Florence, Via della Lastruccia 3, 50019, Sesto Fiorentino, Italy
| | - Luca Sgheri
- Istituto per le Applicazioni del Calcolo, Sezione di Firenze,
CNR, Via Madonna del Piano 10, 50019 Sesto Fiorentino, Italy
| |
Collapse
|
55
|
Abstract
The energy landscapes of proteins are highly complex and can be influenced by changes in physical and chemical conditions under which the protein is studied. The redox enzyme cytochrome P450cam undergoes a multistep catalytic cycle wherein two electrons are transferred to the heme group and the enzyme visits several conformational states. Using paramagnetic NMR spectroscopy with a lanthanoid tag, we show that the enzyme bound to its redox partner, putidaredoxin, is in a closed state at ambient temperature in solution. This result contrasts with recent crystal structures of the complex, which suggest that the enzyme opens up when bound to its partner. The closed state supports a model of catalysis in which the substrate is locked in the active site pocket and the enzyme acts as an insulator for the reactive intermediates of the reaction.
Collapse
|
56
|
Pilla KB, Leman JK, Otting G, Huber T. Capturing conformational States in proteins using sparse paramagnetic NMR data. PLoS One 2015; 10:e0127053. [PMID: 25992808 PMCID: PMC4436263 DOI: 10.1371/journal.pone.0127053] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2015] [Accepted: 04/10/2015] [Indexed: 12/20/2022] Open
Abstract
Capturing conformational changes in proteins or protein-protein complexes is a challenge for both experimentalists and computational biologists. Solution nuclear magnetic resonance (NMR) is unique in that it permits structural studies of proteins under greatly varying conditions, and thus allows us to monitor induced structural changes. Paramagnetic effects are increasingly used to study protein structures as they give ready access to rich structural information of orientation and long-range distance restraints from the NMR signals of backbone amides, and reliable methods have become available to tag proteins with paramagnetic metal ions site-specifically and at multiple sites. In this study, we show how sparse pseudocontact shift (PCS) data can be used to computationally model conformational states in a protein system, by first identifying core structural elements that are not affected by the environmental change, and then computationally completing the remaining structure based on experimental restraints from PCS. The approach is demonstrated on a 27 kDa two-domain NS2B-NS3 protease system of the dengue virus serotype 2, for which distinct closed and open conformational states have been observed in crystal structures. By changing the input PCS data, the observed conformational states in the dengue virus protease are reproduced without modifying the computational procedure. This data driven Rosetta protocol enables identification of conformational states of a protein system, which are otherwise difficult to obtain either experimentally or computationally.
Collapse
Affiliation(s)
- Kala Bharath Pilla
- Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
| | - Julia Koehler Leman
- Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, MD, 21218, United States of America
| | - Gottfried Otting
- Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
| | - Thomas Huber
- Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
- * E-mail:
| |
Collapse
|
57
|
Park SH, Wang V, Radoicic J, De Angelis AA, Berkamp S, Opella SJ. Paramagnetic relaxation enhancement of membrane proteins by incorporation of the metal-chelating unnatural amino acid 2-amino-3-(8-hydroxyquinolin-3-yl)propanoic acid (HQA). JOURNAL OF BIOMOLECULAR NMR 2015; 61:185-96. [PMID: 25430059 PMCID: PMC4398598 DOI: 10.1007/s10858-014-9884-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2014] [Accepted: 11/20/2014] [Indexed: 05/16/2023]
Abstract
The use of paramagnetic constraints in protein NMR is an active area of research because of the benefits of long-range distance measurements (>10 Å). One of the main issues in successful execution is the incorporation of a paramagnetic metal ion into diamagnetic proteins. The most common metal ion tags are relatively long aliphatic chains attached to the side chain of a selected cysteine residue with a chelating group at the end where it can undergo substantial internal motions, decreasing the accuracy of the method. An attractive alternative approach is to incorporate an unnatural amino acid that binds metal ions at a specific site on the protein using the methods of molecular biology. Here we describe the successful incorporation of the unnatural amino acid 2-amino-3-(8-hydroxyquinolin-3-yl)propanoic acid (HQA) into two different membrane proteins by heterologous expression in E. coli. Fluorescence and NMR experiments demonstrate complete replacement of the natural amino acid with HQA and stable metal chelation by the mutated proteins. Evidence of site-specific intra- and inter-molecular PREs by NMR in micelle solutions sets the stage for the use of HQA incorporation in solid-state NMR structure determinations of membrane proteins in phospholipid bilayers.
Collapse
|
58
|
Lee MD, Loh CT, Shin J, Chhabra S, Dennis ML, Otting G, Swarbrick JD, Graham B. Compact, hydrophilic, lanthanide-binding tags for paramagnetic NMR spectroscopy. Chem Sci 2015; 6:2614-2624. [PMID: 29560247 PMCID: PMC5812434 DOI: 10.1039/c4sc03892d] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Accepted: 02/25/2015] [Indexed: 01/18/2023] Open
Abstract
The design, synthesis and evaluation of four novel lanthanide-binding tags for paramagnetic NMR spectroscopy are reported.
The design, synthesis and evaluation of four novel lanthanide-binding tags for paramagnetic NMR spectroscopy are reported. Each tag is based on the ((2S,2′S,2′′S,2′′′S)-1,1′,1′′,1′′′-(1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrayl)tetrakis(propan-2-ol)) scaffold, featuring small chiral alcohol coordinating pendants to minimise the size and hydrophobic character of each tag. The tags feature different linkers of variable length for conjugation to protein via a single cysteine residue. Each tag's ability to induce pseudocontact shifts (PCS) was assessed on a ubiquitin A28C mutant. Two enantiomeric tags of particular note, C7 and C8, produced significantly larger Δχ-tensors compared to a previously developed tag, C1, attributed to the extremely short linker utilised, limiting the mobility of the bound lanthanide ion. The C7 and C8 tags' capacity to induce PCSs was further demonstrated on GB1 Q32C and 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase (HPPK) S112C/C80A mutants. Whilst factors such as the choice of lanthanide ion, pH and site of conjugation influence the size of the PCSs obtained, the tags represent a significant advance in the field.
Collapse
Affiliation(s)
- M D Lee
- Monash Institute of Pharmaceutical Sciences , Monash University , Parkville , VIC 3052 , Australia . ;
| | - C-T Loh
- Research School of Chemistry , Australian National University , Canberra , ACT 0200 , Australia
| | - J Shin
- Monash Institute of Pharmaceutical Sciences , Monash University , Parkville , VIC 3052 , Australia . ;
| | - S Chhabra
- Monash Institute of Pharmaceutical Sciences , Monash University , Parkville , VIC 3052 , Australia . ;
| | - M L Dennis
- Monash Institute of Pharmaceutical Sciences , Monash University , Parkville , VIC 3052 , Australia . ;
| | - G Otting
- Research School of Chemistry , Australian National University , Canberra , ACT 0200 , Australia
| | - J D Swarbrick
- Monash Institute of Pharmaceutical Sciences , Monash University , Parkville , VIC 3052 , Australia . ;
| | - B Graham
- Monash Institute of Pharmaceutical Sciences , Monash University , Parkville , VIC 3052 , Australia . ;
| |
Collapse
|
59
|
Loh CT, Graham B, Abdelkader EH, Tuck KL, Otting G. Generation of pseudocontact shifts in proteins with lanthanides using small "clickable" nitrilotriacetic acid and iminodiacetic acid tags. Chemistry 2015; 21:5084-92. [PMID: 25676727 DOI: 10.1002/chem.201406274] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2014] [Indexed: 01/07/2023]
Abstract
Pseudocontact shifts (PCS) induced by paramagnetic lanthanide ions provide unique long-range structural information in nuclear magnetic resonance (NMR) spectra, but the site-specific attachment of lanthanide tags to proteins remains a challenge. Here we incorporated p-azido-phenylalanine (AzF) site-specifically into the proteins ubiquitin and GB1, and ligated the AzF residue with alkyne derivatives of small nitrilotriacetic acid and iminodiacetic acid tags using the Cu(I) -catalysed "click" reaction. These tags form lanthanide complexes with no or only a small net charge and produced sizeable PCSs with paramagnetic lanthanide ions in all mutants tested. The PCSs were readily fitted by single magnetic susceptibility anisotropy tensors. Protein precipitation during the click reaction was greatly alleviated by the presence of 150 mM NaCl.
Collapse
Affiliation(s)
- Choy-Theng Loh
- Research School of Chemistry, Australian National University, Canberra ACT 2601 (Australia)
| | | | | | | | | |
Collapse
|
60
|
Rinaldelli M, Carlon A, Ravera E, Parigi G, Luchinat C. FANTEN: a new web-based interface for the analysis of magnetic anisotropy-induced NMR data. JOURNAL OF BIOMOLECULAR NMR 2015; 61:21-34. [PMID: 25416616 DOI: 10.1007/s10858-014-9877-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Accepted: 11/15/2014] [Indexed: 05/17/2023]
Abstract
Pseudocontact shifts (PCSs) and residual dipolar couplings (RDCs) arising from the presence of paramagnetic metal ions in proteins as well as RDCs due to partial orientation induced by external orienting media are nowadays routinely measured as a part of the NMR characterization of biologically relevant systems. PCSs and RDCs are becoming more and more popular as restraints (1) to determine and/or refine protein structures in solution, (2) to monitor the extent of conformational heterogeneity in systems composed of rigid domains which can reorient with respect to one another, and (3) to obtain structural information in protein-protein complexes. The use of both PCSs and RDCs proceeds through the determination of the anisotropy tensors which are at the origin of these NMR observables. A new user-friendly web tool, called FANTEN (Finding ANisotropy TENsors), has been developed for the determination of the anisotropy tensors related to PCSs and RDCs and has been made freely available through the WeNMR ( http://fanten-enmr.cerm.unifi.it:8080 ) gateway. The program has many new features not available in other existing programs, among which the possibility of a joint analysis of several sets of PCS and RDC data and the possibility to perform rigid body minimizations.
Collapse
Affiliation(s)
- Mauro Rinaldelli
- CERM and Department of Chemistry "Ugo Schiff", University of Florence, via Sacconi 6, Sesto Fiorentino, Florence, Italy
| | | | | | | | | |
Collapse
|
61
|
Novikov VV, Pavlov AA, Belov AS, Vologzhanina AV, Savitsky A, Voloshin YZ. Transition Ion Strikes Back: Large Magnetic Susceptibility Anisotropy in Cobalt(II) Clathrochelates. J Phys Chem Lett 2014; 5:3799-803. [PMID: 26278750 DOI: 10.1021/jz502011z] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Transition-metal complexes are rarely considered as paramagnetic tags for NMR spectroscopy due to them generally having relatively low magnetic anisotropy. Here we report cobalt(II) cage complexes with the largest (among the transition-metal complexes) axial anisotropy of magnetic susceptibility, reaching as high as 12.6 × 10(-32) m(3) at room temperature. This remarkable anisotropy, which results from an unusual trigonal prismatic geometry of the complexes and translates into large negative value of the zero-field splitting energy, is high enough to promote reliable paramagnetic pseudocontact shifts at the distance beyond 2 nm. Our finding paves the way toward the applications of cobalt(II) clathrochelates as future paramagnetic tags. Given the incredible stability and functionalization versatility of clathrochelates, the fine-tuning of the caging ligand may lead to new chemically stable mononuclear single-molecule magnets, for which magnetic anisotropy is of importance.
Collapse
Affiliation(s)
- Valentin V Novikov
- †Nesmeyanov Institute of Organoelement Compounds, RAS, Vavilova str. 28, 119991 Moscow, Russia
| | - Alexander A Pavlov
- †Nesmeyanov Institute of Organoelement Compounds, RAS, Vavilova str. 28, 119991 Moscow, Russia
| | - Alexander S Belov
- †Nesmeyanov Institute of Organoelement Compounds, RAS, Vavilova str. 28, 119991 Moscow, Russia
| | - Anna V Vologzhanina
- †Nesmeyanov Institute of Organoelement Compounds, RAS, Vavilova str. 28, 119991 Moscow, Russia
| | - Anton Savitsky
- ‡Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Yan Z Voloshin
- †Nesmeyanov Institute of Organoelement Compounds, RAS, Vavilova str. 28, 119991 Moscow, Russia
| |
Collapse
|
62
|
|
63
|
Prestegard JH, Agard DA, Moremen KW, Lavery LA, Morris LC, Pederson K. Sparse labeling of proteins: structural characterization from long range constraints. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2014; 241:32-40. [PMID: 24656078 PMCID: PMC3964372 DOI: 10.1016/j.jmr.2013.12.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2013] [Revised: 12/17/2013] [Accepted: 12/19/2013] [Indexed: 05/07/2023]
Abstract
Structural characterization of biologically important proteins faces many challenges associated with degradation of resolution as molecular size increases and loss of resolution improving tools such as perdeuteration when non-bacterial hosts must be used for expression. In these cases, sparse isotopic labeling (single or small subsets of amino acids) combined with long range paramagnetic constraints and improved computational modeling offer an alternative. This perspective provides a brief overview of this approach and two discussions of potential applications; one involving a very large system (an Hsp90 homolog) in which perdeuteration is possible and methyl-TROSY sequences can potentially be used to improve resolution, and one involving ligand placement in a glycosylated protein where resolution is achieved by single amino acid labeling (the sialyltransferase, ST6Gal1). This is not intended as a comprehensive review, but as a discussion of future prospects that promise impact on important questions in the structural biology area.
Collapse
Affiliation(s)
- James H Prestegard
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA 30602, United States.
| | - David A Agard
- The Howard Hughes Medical Institute, Dept. Biochem. & Biophys., Univ. Calif. San Francisco, San Francisco, CA 94158, United States
| | - Kelley W Moremen
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA 30602, United States
| | - Laura A Lavery
- The Howard Hughes Medical Institute, Dept. Biochem. & Biophys., Univ. Calif. San Francisco, San Francisco, CA 94158, United States
| | - Laura C Morris
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA 30602, United States
| | - Kari Pederson
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA 30602, United States
| |
Collapse
|
64
|
Ciofi-Baffoni S, Gallo A, Muzzioli R, Piccioli M. The IR-¹⁵N-HSQC-AP experiment: a new tool for NMR spectroscopy of paramagnetic molecules. JOURNAL OF BIOMOLECULAR NMR 2014; 58:123-8. [PMID: 24414179 DOI: 10.1007/s10858-013-9810-2] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Accepted: 12/27/2013] [Indexed: 05/22/2023]
Abstract
A crucial factor for the understanding of structure-function relationships in metalloproteins is the identification of NMR signals from residues surrounding the metal cofactor. When the latter is paramagnetic, the NMR information in the proximity of the metal center may be scarce, because fast nuclear relaxation quenches signal intensity and coherence transfer efficiency. To identify residues at a short distance from a paramagnetic center, we developed a modified version of the ¹⁵N-HSQC experiment where (1) an inversion recovery filter is added prior to HSQC, (2) the INEPT period has been optimized according to fast relaxation of interested spins, (3) the inverse INEPT has been eliminated and signals acquired as antiphase doublets. The experiment has been successfully tested on a human [Fe₂S₂] protein which is involved in the biogenesis of iron-sulfur proteins. Thirteen HN resonances, unobserved with conventional HSQC experiments, could be identified. The structural arrangement of the protein scaffold in the proximity of the Fe/S cluster is fundamental to comprehend the molecular processes responsible for the transfer of Fe/S groups in the iron-sulfur protein assembly machineries.
Collapse
Affiliation(s)
- Simone Ciofi-Baffoni
- Magnetic Resonance Center and Department of Chemistry, University of Florence, Via Luigi Sacconi 6, 50019, Sesto Fiorentino, Florence, Italy
| | | | | | | |
Collapse
|
65
|
Huang F, Pei YY, Zuo HH, Chen JL, Yang Y, Su XC. Bioconjugation of proteins with a paramagnetic NMR and fluorescent tag. Chemistry 2013; 19:17141-9. [PMID: 24307370 DOI: 10.1002/chem.201302273] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2013] [Indexed: 11/05/2022]
Abstract
Site-specific labeling of proteins with lanthanide ions offers great opportunities for investigating the structure, function, and dynamics of proteins by virtue of the unique properties of lanthanides. Lanthanide-tagged proteins can be studied by NMR, X-ray, fluorescence, and EPR spectroscopy. However, the rigidity of a lanthanide tag in labeling of proteins plays a key role in the determination of protein structures and interactions. Pseudocontact shift (PCS) and paramagnetic relaxation enhancement (PRE) are valuable long-range structure restraints in structural-biology NMR spectroscopy. Generation of these paramagnetic restraints generally relies on site-specific tagging of the target proteins with paramagnetic species. To avoid nonspecific interaction between the target protein and paramagnetic tag and achieve reliable paramagnetic effects, the rigidity, stability, and size of lanthanide tag is highly important in paramagnetic labeling of proteins. Here 4'-mercapto-2,2':6',2''-terpyridine-6,6''-dicarboxylic acid (4MTDA) is introduced as a a rigid paramagnetic and fluorescent tag which can be site-specifically attached to a protein by formation of a disulfide bond. 4MTDA can be readily immobilized by coordination of the protein side chain to the lanthanide ion. Large PCSs and RDCs were observed for 4MTDA-tagged proteins in complexes with paramagnetic lanthanide ions. At an excitation wavelength of 340 nm, the complex formed by protein-4MTDA and Tb(3+) produces high fluorescence with the main emission at 545 nm. These interesting features of 4MTDA make it a very promising tag that can be exploited in NMR, fluorescence, and EPR spectroscopic studies on protein structure, interaction, and dynamics.
Collapse
Affiliation(s)
- Feng Huang
- State Key Laboratory of Elemento-organic Chemistry and College of Chemistry, Nankai University, Weijin Road 94, Tianjin 300071 (P. R. China), Fax: (+86) 22-23500623
| | | | | | | | | | | |
Collapse
|