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Löhr F, Gebel J, Henrich E, Hein C, Dötsch V. Towards complete polypeptide backbone NH assignment via combinatorial labeling. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2019; 302:50-63. [PMID: 30959416 DOI: 10.1016/j.jmr.2019.03.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Revised: 03/27/2019] [Accepted: 03/28/2019] [Indexed: 06/09/2023]
Abstract
Combinatorial selective isotope labeling is a valuable tool to facilitate polypeptide backbone resonance assignment in cases of low sensitivity or extensive chemical shift degeneracy. It involves recording of 15N-HSQC and 2D HN-projections of triple-resonance spectra on a limited set of samples containing different combinations of labeled and unlabeled amino acid types. Using labeling schemes in which the three backbone heteronuclei (amide nitrogen, α-carbon and carbonyl carbon) are enriched in 15N or 13C isotopes - individually as well as simultaneously - usually yields abundant amino-acid type information of consecutive residues i and i - 1. Although this results in a large number of anchor points that can be used in the sequential assignment process, for most amide signals the exact positioning of the corresponding residue the polypeptide sequence still relies on matching intra- and interresidual 13C chemical shifts obtained from 3D spectra. An obvious way to obtain more sequence-specific assignments directly with combinatorial labeling would be to increase the number of samples. This is, however, undesirable because of increased sample preparation efforts and costs. Irrespective of the number of samples, unambiguous assignments cannot be accomplished for i - 1/i pairs that are not unique in the sequence. Here we show that the ambiguity for non-unique pairs can be resolved by including information about the labeling state of residues i + 1 and i - 2. Application to a 35-residue peptide resulted in complete assignments of all detectable signals in the 15N HSQC which, due to its repetitive sequence and 13C chemical shift degeneracies, was difficult to achieve by other means. For a medium-sized protein (165 residues, rotational correlation time 8.2 ns) the improved protocol allowed the extent of backbone amide assignment to be expanded to 88% solely using a suite of 2D 1H-15N correlated spectra.
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Affiliation(s)
- Frank Löhr
- Institute of Biophysical Chemistry & Center for Biomolecular Magnetic Resonance, Goethe University, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany
| | - Jakob Gebel
- Institute of Biophysical Chemistry & Center for Biomolecular Magnetic Resonance, Goethe University, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany
| | - Erik Henrich
- Institute of Biophysical Chemistry & Center for Biomolecular Magnetic Resonance, Goethe University, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany
| | - Christopher Hein
- Institute of Biophysical Chemistry & Center for Biomolecular Magnetic Resonance, Goethe University, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany
| | - Volker Dötsch
- Institute of Biophysical Chemistry & Center for Biomolecular Magnetic Resonance, Goethe University, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany.
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Henrich E, Löhr F, Mezhyrova J, Laguerre A, Bernhard F, Dötsch V. Synthetic Biology-Based Solution NMR Studies on Membrane Proteins in Lipid Environments. Methods Enzymol 2018; 614:143-185. [PMID: 30611423 DOI: 10.1016/bs.mie.2018.08.019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Although membrane proteins are in the focus of biochemical research for many decades the general knowledge of this important class is far behind soluble proteins. Despite several recent technical developments, the most challenging feature still is the generation of high-quality samples in environments suitable for the selected application. Reconstitution of membrane proteins into lipid bilayers will generate the most native-like environment and is therefore commonly desired. However, it poses tremendous problems to solution-state NMR analysis due to the dramatic increase in particle size resulting in high rotational correlation times. Nevertheless, a few promising strategies for the solution NMR analysis of membrane inserted proteins are emerging and will be discussed in this chapter. We focus on the generation of membrane protein samples in nanodisc membranes by cell-free systems and will describe the characteristic advantages of that platform in providing tailored protein expression and folding environments. We indicate frequent problems that have to be overcome in cell-free synthesis, nanodisc preparation, and customization for samples dedicated for solution-state NMR. Detailed instructions for sample preparation are given, and solution NMR approaches suitable for membrane proteins in bilayers are compiled. We further discuss the current strategies applied for signal detection from such difficult samples and describe the type of information that can be extracted from the various experiments. In summary, a comprehensive guideline for the analysis of membrane proteins in native-like membrane environments by solution-state NMR techniques will be provided.
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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
| | - Frank Löhr
- Institute of Biophysical Chemistry, Centre for Biomolecular Magnetic Resonance, J.W. Goethe-University, Frankfurt am Main, Germany
| | - Julija Mezhyrova
- Institute of Biophysical Chemistry, Centre for Biomolecular Magnetic Resonance, J.W. Goethe-University, Frankfurt am Main, Germany
| | - Aisha Laguerre
- 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
| | - Volker Dötsch
- Institute of Biophysical Chemistry, Centre for Biomolecular Magnetic Resonance, J.W. Goethe-University, Frankfurt am Main, Germany.
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Hein C, Löhr F, Schwarz D, Dötsch V. Acceleration of protein backbone NMR assignment by combinatorial labeling: Application to a small molecule binding study. Biopolymers 2017; 107. [PMID: 28035667 DOI: 10.1002/bip.23013] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Revised: 12/15/2016] [Accepted: 12/16/2016] [Indexed: 12/21/2022]
Abstract
Selective labeling with stable isotopes has long been recognized as a valuable tool in protein NMR to alleviate signal overlap and sensitivity limitations. In this study, combinatorial 15 N-, 13 Cα -, and 13 C'-selective labeling has been used during the backbone assignment of human cyclophilin D to explore binding of an inhibitor molecule. Using a cell-free expression system, a scheme that involves 15 N, 1-13 C, 2-13 C, fully 15 N/13 C, and unlabeled amino acids was optimized to gain a maximum of assignment information from three samples. This scheme was combined with time-shared triple-resonance NMR experiments, which allows a fast and efficient backbone assignment by giving the unambiguous assignment of unique amino acid pairs in the protein, the identity of ambiguous pairs and information about all 19 non-proline amino acid types. It is therefore well suited for binding studies where de novo assignments of amide 1 H and 15 N resonances need to be obtained, even in cases where sensitivity is the limiting factor.
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Affiliation(s)
- Christopher Hein
- Institute of Biophysical Chemistry and Center for Biomolecular Magnetic Resonance, Goethe University, Frankfurt, 60438, Germany
| | - Frank Löhr
- Institute of Biophysical Chemistry and Center for Biomolecular Magnetic Resonance, Goethe University, Frankfurt, 60438, Germany
| | - Daniel Schwarz
- Merck KGaA, Discovery Pharmacology, Global Research and Development, Darmstadt, 64293, Germany
| | - Volker Dötsch
- Institute of Biophysical Chemistry and Center for Biomolecular Magnetic Resonance, Goethe University, Frankfurt, 60438, Germany
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Löhr F, Tumulka F, Bock C, Abele R, Dötsch V. An extended combinatorial 15N, 13Cα, and 13C' labeling approach to protein backbone resonance assignment. JOURNAL OF BIOMOLECULAR NMR 2015; 62:263-79. [PMID: 25953311 DOI: 10.1007/s10858-015-9941-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Accepted: 04/28/2015] [Indexed: 05/07/2023]
Abstract
Solution NMR studies of α-helical membrane proteins are often complicated by severe spectral crowding. In addition, hydrophobic environments like detergent micelles, isotropic bicelles or nanodiscs lead to considerably reduced molecular tumbling rates which translates into line-broadening and low sensitivity. Both difficulties can be addressed by selective isotope labeling methods. In this publication, we propose a combinatorial protocol that utilizes four different classes of labeled amino acids, in which the three backbone heteronuclei (amide nitrogen, α-carbon and carbonyl carbon) are enriched in (15)N or (13)C isotopes individually as well as simultaneously. This results in eight different combinations of dipeptides giving rise to cross peaks in (1)H-(15)N correlated spectra. Their differentiation is achieved by recording a series of HN-detected 2D triple-resonance spectra. The utility of this new scheme is demonstrated with a homodimeric 142-residue membrane protein in DHPC micelles. Restricting the number of selectively labeled samples to three allowed the identification of the amino-acid type for 77 % and provided sequential information for 47 % of its residues. This enabled us to complete the backbone resonance assignment of the uniformly labeled protein merely with the help of a 3D HNCA spectrum, which can be collected with reasonable sensitivity even for relatively large, non-deuterated proteins.
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Affiliation(s)
- Frank Löhr
- Institute of Biophysical Chemistry and Center for Biomolecular Magnetic Resonance, Goethe University, Max-von-Laue-Str. 9, 60438, Frankfurt, Germany
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Löhr F, Laguerre A, Bock C, Reckel S, Connolly PJ, Abdul-Manan N, Tumulka F, Abele R, Moore JM, Dötsch V. Time-shared experiments for efficient assignment of triple-selectively labeled proteins. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2014; 248:81-95. [PMID: 25442777 PMCID: PMC4254601 DOI: 10.1016/j.jmr.2014.09.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Revised: 09/10/2014] [Accepted: 09/16/2014] [Indexed: 05/20/2023]
Abstract
Combinatorial triple-selective labeling facilitates the NMR assignment process for proteins that are subject to signal overlap and insufficient signal-to-noise in standard triple-resonance experiments. Aiming at maximum amino-acid type and sequence-specific information, the method represents a trade-off between the number of selectively labeled samples that have to be prepared and the number of spectra to be recorded per sample. In order to address the demand of long measurement times, we here propose pulse sequences in which individual phase-shifted transients are stored separately and recombined later to produce several 2D HN(CX) type spectra that are usually acquired sequentially. Sign encoding by the phases of (13)C 90° pulses allows to either select or discriminate against (13)C' or (13)C(α) spins coupled to (15)N. As a result, (1)H-(15)N correlation maps of the various isotopomeric species present in triple-selectively labeled proteins are deconvoluted which in turn reduces problems due to spectral overlap. The new methods are demonstrated with four different membrane proteins with rotational correlation times ranging from 18 to 52 ns.
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Affiliation(s)
- Frank Löhr
- Institute of Biophysical Chemistry & Center for Biomolecular Magnetic Resonance, Goethe University, Max-von-Laue-Str. 9, D-60438 Frankfurt, Germany
| | - Aisha Laguerre
- Institute of Biophysical Chemistry & Center for Biomolecular Magnetic Resonance, Goethe University, Max-von-Laue-Str. 9, D-60438 Frankfurt, Germany
| | - Christoph Bock
- Institute of Biochemistry, Goethe University, Max-von-Laue-Str. 9, D-60438 Frankfurt, Germany
| | - Sina Reckel
- Institute of Biophysical Chemistry & Center for Biomolecular Magnetic Resonance, Goethe University, Max-von-Laue-Str. 9, D-60438 Frankfurt, Germany
| | | | | | - Franz Tumulka
- Institute of Biochemistry, Goethe University, Max-von-Laue-Str. 9, D-60438 Frankfurt, Germany
| | - Rupert Abele
- Institute of Biochemistry, Goethe University, Max-von-Laue-Str. 9, D-60438 Frankfurt, Germany
| | | | - Volker Dötsch
- Institute of Biophysical Chemistry & Center for Biomolecular Magnetic Resonance, Goethe University, Max-von-Laue-Str. 9, D-60438 Frankfurt, Germany.
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Hiroaki H, Umetsu Y, Nabeshima YI, Hoshi M, Kohda D. A simplified recipe for assigning amide NMR signals using combinatorial 14N amino acid inverse-labeling. ACTA ACUST UNITED AC 2011; 12:167-74. [PMID: 21866395 DOI: 10.1007/s10969-011-9116-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2011] [Accepted: 08/02/2011] [Indexed: 11/27/2022]
Abstract
Assignment of backbone amide proton resonances is one of the most time-consuming stages of any protein NMR study when the protein samples behave non-ideally. A robust and convenient NMR procedure for analyzing spectra of marginal-to-low quality is helpful for high-throughput structure determination. The 14N selective- and inverse-labeling method is a candidate solution. Here, we present a simplified protocol for assigning protein backbone amide NMR signals. When 14N inversely labeled residues are present in a protein, their backbone NH cross peaks vanish from the protein's 1H-(15)N HSQC spectrum, and thus, their chemical shifts can be readily identified by a process of elimination. Some metabolically related amino acids, for example, Ile, Leu, and Val, cannot be individually incorporated but can be inversely labeled together. We optimized and simplified the protocol and M9-based medium formula for the 14N selective- and inverse-labeling method without any additives. Our approach should be cost-effective, because the method could be additively applied stepwise, even when the proteins of interest were found to be non-ideal.
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Affiliation(s)
- Hidekazu Hiroaki
- Division of Structural Biology, Kobe University Graduate School of Medicine, 7-5-1, Kusunoki-cho, Chuo, Kobe, 650-0017, Japan.
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Latypov RF, Liu D, Gunasekaran K, Harvey TS, Razinkov VI, Raibekas AA. Structural and thermodynamic effects of ANS binding to human interleukin-1 receptor antagonist. Protein Sci 2008; 17:652-63. [PMID: 18305195 DOI: 10.1110/ps.073332408] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Although 8-anilinonaphthalene-1-sulfonic acid (ANS) is frequently used in protein folding studies, the structural and thermodynamic effects of its binding to proteins are not well understood. Using high-resolution two-dimensional NMR and human interleukin-1 receptor antagonist (IL-1ra) as a model protein, we obtained detailed information on ANS-protein interactions in the absence and presence of urea. The effects of ambient to elevated temperatures on the affinity and specificity of ANS binding were assessed from experiments performed at 25 degrees C and 37 degrees C. Overall, the affinity of ANS was lower at 37 degrees C compared to 25 degrees C, but no significant change in the site specificity of binding was observed from the chemical shift perturbation data. The same site-specific binding was evident in the presence of 5.2 M urea, well within the unfolding transition region, and resulted in selective stabilization of the folded state. Based on the two-state denaturation mechanism, ANS-dependent changes in the protein stability were estimated from relative intensities of two amide resonances specific to the folded and unfolded states of IL-1ra. No evidence was found for any ANS-induced partially denatured or aggregated forms of IL-1ra throughout the experimental conditions, consistent with a cooperative and reversible denaturation process. The NMR results support earlier observations on the tendency of ANS to interact with solvent-exposed positively charged sites on proteins. Under denaturing conditions, ANS binding appears to be selective to structured states rather than unfolded conformations. Interestingly, the binding occurs within a previously identified aggregation-critical region in IL-1ra, thus providing an insight into ligand-dependent protein aggregation.
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Affiliation(s)
- Ramil F Latypov
- Department of Pharmaceutics, Amgen Inc., Seattle, Washington 98119-3105, USA.
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Ambrosetti DC, Palla E, Mirtella A, Galeotti C, Solito E, Navarra P, Parente L, Melli M. Synthetic alleles at position 121 define a functional domain of human interleukin-1 beta. EUROPEAN JOURNAL OF BIOCHEMISTRY 1996; 238:308-16. [PMID: 8681939 DOI: 10.1111/j.1432-1033.1996.0308z.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The non-conservative substitution of the tyrosine residue at position 121 of human interleukin-1 beta (IL-1 beta) generates protein mutants showing strong reduction of the capacity to induce (a) prostaglandin E2 (PGE2) release from fibroblasts and smooth muscle cells, (b) murine T-cells proliferation and (c) activation of interleukin-6 (IL-6) gene expression. It is generally accepted that these functions are mediated by the type-I interleukin-1 receptor (IL-1RI). However, the mutant proteins maintain the binding affinity to the types-I and II IL-1 receptors, which is the same as the control IL-1 beta, suggesting that this amino acid substitution does not alter the structure of the molecule, except locally. Thus we have identified a new functional site of IL-1 beta different from the known receptor binding region, responsible for fundamental IL-1 beta functions. Moreover, we show that the same mutants maintain at least two hypothalamic functions, that is, the in vitro short-term PGE2 release from rat hypothalamus and the induction of fever in rabbits. This result suggests that there is yet another site of the molecule responsible for the hypothalamic functions, implying that multiple active sites on the IL-1 beta molecule, possibly binding to more than one receptor chain, trigger different signals.
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Affiliation(s)
- D C Ambrosetti
- Department of Molecular Biology, Immunobiological Research Institute, Siena, Italy
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9
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Simoncsits A, Bristulf J, Tjörnhammar ML, Cserzö M, Pongor S, Rybakina E, Gatti S, Bartfai T. Deletion mutants of human interleukin 1 beta with significantly reduced agonist properties: search for the agonist/antagonist switch in ligands to the interleukin 1 receptors. Cytokine 1994; 6:206-14. [PMID: 8032002 DOI: 10.1016/1043-4666(94)90043-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The existence of an endogenous high affinity interleukin 1 receptor antagonist (IL-1ra) suggests that this molecule lacks some structural motif(s) which are present in the closely homologous agonist interleukin 1 beta (IL-1 beta) and which serve as the 'agonist switch' causing signal transduction by the agonist-receptor complex. The primary sequence alignment of IL-1 beta and IL-1ra sequences from different species reveals a six amino acid long motif that is quasi conserved among IL-1 beta sequences, but is missing from the IL-1ra sequences. The three-dimensional structure of human IL-1 beta was used as a template for building structural models of deletion mutants (delta SND 52-54 and delta EESNDK 50-55) using molecular graphics. These models indicated that the middle three residues SND 52-54 from the EESNDK 50-55 loop may be deleted without causing major changes in the tertiary structure of the mutant as compared to that of IL-1 beta. Residues SND 52-54 from the above loop were deleted. When compared with IL-1 beta the IL-1 beta-delta SND analog (delta SND 52-54) binds with the same affinity to type 2 IL-1 receptor but with a more than 10-fold lower affinity to type 1 IL-1 receptor. Despite of this small decrease in affinity at the type 1 receptor the delta SND 52-54 has a 1000-fold lower biological activity than IL-1 beta when tested in a thymocyte activating factor assay.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- A Simoncsits
- Department of Neurochemistry and Neurotoxicology, Stockholm University, Sweden
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Fasina G, Verdoliva A, Cassani G, Melli M. Binding of type I IL-1 beta receptor fragment 151-162 to interleukin-1 beta. Growth Factors 1994; 10:99-106. [PMID: 8068354 DOI: 10.3109/08977199409010983] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The relevance of hydropathically complementary sequences in ligand receptor interactions has been evaluated in the interleukin-1 beta/receptor type I case. Computer assisted comparison of the hydropathic profiles of IL-1 beta and its receptor (type I) identified residues 88-99 in IL-1 beta and 151-162 in the receptor as the sequences pair characterized by the highest level of hydropathic complementarity. These fragments, once produced by chemical synthesis and derivatized with biotin, displayed specific recognition properties for each other, as detected by solid phase binding assays. Binding between the two fragments occurred independently from the assay format, was saturable and specifically inhibited by unlabeled peptides. Receptor fragment (151-162) derivatized with biotin recognized also full length recombinant IL-1 beta, and binding was inhibited to 50% in the presence of 3 microM IL-1 beta (88-99) peptide. Interaction specificity was further confirmed by the non competitive effect on the interaction of a sequence scrambled IL-1 beta (88-99) peptide. In a similar way, full length biotinylated IL-1 beta recognized immobilized IL-1 beta receptor fragment (151-162), and this interaction was diminished in the presence of unlabeled receptor fragment or IL-1 beta Results indicate that IL-1 beta receptor fragment (151-162) binds IL-1 beta recognizing the IL-1 beta (88-99) sequence, thus suggesting a possible role of these fragments in the protein/receptor recognition surface.
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Affiliation(s)
- G Fasina
- Protein Engineering Unit, TECNOGEN S.C.p.A., Milano, Italy
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Palla E, Bensi G, Solito E, Buonamassa D, Fassina G, Raugei G, Spano F, Galeotti C, Mora M, Domenighini M. Loop substitution as a tool to identify active sites of interleukin-1 beta. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(19)38675-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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12
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Stockman BJ, Scahill TA, Roy M, Ulrich EL, Strakalaitis NA, Brunner DP, Yem AW, Deibel MR. Secondary structure and topology of interleukin-1 receptor antagonist protein determined by heteronuclear three-dimensional NMR spectroscopy. Biochemistry 1992; 31:5237-45. [PMID: 1534997 DOI: 10.1021/bi00138a001] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Interleukin-1 (IL-1) proteins, such as IL-1 beta, play a key role in immune and inflammatory responses. Interaction of these cytokines with the IL-1 receptor induces a variety of biological changes in neurologic, metabolic, hematologic, and endocrinologic systems. Interleukin-1 receptor antagonist protein (IRAP) is a naturally occurring inhibitor of the interleukin-1 receptor. The 153-residue protein binds to the receptor with an affinity similar to that of IL-1 beta but does not elicit any physiological responses. As a first step toward understanding IRAP's mode of action, we have used multidimensional, heteronuclear NMR spectroscopy to determine the antagonist's solution secondary structure and global fold. Using a combination of 3D 1H-15N NOESY-HMQC and TOCSY-HMQC and 3D 1H-15N-13C HNCA and HN(CO)CA experiments on uniformly 15N- or doubly 13C/15N-enriched IRAP, we have made resonance assignments for more than 90% of the main-chain atoms. Analysis of short- and long-range NOE's indicates that IRAP is predominantly beta-sheet, with the same overall topology as IL-1 beta but with different regions of the primary sequence comprising the beta-strands. Two short helical segments also were identified. The 14% sequence identity between IL-1 beta and IRAP increases to 25% when differences in the locations of secondary structure elements in the primary sequences are taken into account. Still, numerous differences in side chains, which ultimately play a major role in receptor interaction, exist.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- B J Stockman
- Upjohn Laboratories, Upjohn Company, Kalamazoo, Michigan 49007
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