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Keceli G, Majumdar A, Thorpe CN, Jun S, Tocchetti CG, Lee DI, Mahaney JE, Paolocci N, Toscano JP. Nitroxyl (HNO) targets phospholamban cysteines 41 and 46 to enhance cardiac function. J Gen Physiol 2019; 151:758-770. [PMID: 30842219 PMCID: PMC6571998 DOI: 10.1085/jgp.201812208] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Accepted: 02/15/2019] [Indexed: 11/20/2022] Open
Abstract
Nitroxyl (HNO) positively modulates myocardial function by accelerating Ca2+ reuptake into the sarcoplasmic reticulum (SR). HNO-induced enhancement of myocardial Ca2+ cycling and function is due to the modification of cysteines in the transmembrane domain of phospholamban (PLN), which results in activation of SR Ca2+-ATPase (SERCA2a) by functionally uncoupling PLN from SERCA2a. However, which cysteines are modified by HNO, and whether HNO induces reversible disulfides or single cysteine sulfinamides (RS(O)NH2) that are less easily reversed by reductants, remain to be determined. Using an 15N-edited NMR method for sulfinamide detection, we first demonstrate that Cys46 and Cys41 are the main targets of HNO reactivity with PLN. Supporting this conclusion, mutation of PLN cysteines 46 and 41 to alanine reduces the HNO-induced enhancement of SERCA2a activity. Treatment of WT-PLN with HNO leads to sulfinamide formation when the HNO donor is in excess, whereas disulfide formation is expected to dominate when the HNO/thiol stoichiometry approaches a 1:1 ratio that is more similar to that anticipated in vivo under normal, physiological conditions. Thus, 15N-edited NMR spectroscopy detects redox changes on thiols that are unique to HNO, greatly advancing the ability to detect HNO footprints in biological systems, while further differentiating HNO-induced post-translational modifications from those imparted by other reactive nitrogen or oxygen species. The present study confirms the potential of HNO as a signaling molecule in the cardiovascular system.
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Affiliation(s)
- Gizem Keceli
- Department of Chemistry, Johns Hopkins University, Baltimore, MD.,Division of Cardiology, Johns Hopkins School of Medicine, Baltimore, MD
| | - Ananya Majumdar
- Biomolecular NMR Center, Johns Hopkins University, Baltimore, MD
| | - Chevon N Thorpe
- Department of Biochemistry, Virginia Polytechnic Institute and State University, Blacksburg, VA
| | - Seungho Jun
- Division of Cardiology, Johns Hopkins School of Medicine, Baltimore, MD
| | | | - Dong I Lee
- Division of Cardiology, Johns Hopkins School of Medicine, Baltimore, MD
| | | | - Nazareno Paolocci
- Division of Cardiology, Johns Hopkins School of Medicine, Baltimore, MD.,Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - John P Toscano
- Department of Chemistry, Johns Hopkins University, Baltimore, MD
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McCaffrey JE, James ZM, Svensson B, Binder BP, Thomas DD. A bifunctional spin label reports the structural topology of phospholamban in magnetically-aligned bicelles. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2016; 262:50-56. [PMID: 26720587 PMCID: PMC4716873 DOI: 10.1016/j.jmr.2015.12.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Revised: 11/25/2015] [Accepted: 12/02/2015] [Indexed: 06/05/2023]
Abstract
We have applied a bifunctional spin label and EPR spectroscopy to determine membrane protein structural topology in magnetically-aligned bicelles, using monomeric phospholamban (PLB) as a model system. Bicelles are a powerful tool for studying membrane proteins by NMR and EPR spectroscopies, where magnetic alignment yields topological constraints by resolving the anisotropic spectral properties of nuclear and electron spins. However, EPR bicelle studies are often hindered by the rotational mobility of monofunctional Cys-linked spin labels, which obscures their orientation relative to the protein backbone. The rigid and stereospecific TOAC label provides high orientational sensitivity but must be introduced via solid-phase peptide synthesis, precluding its use in large proteins. Here we show that a bifunctional methanethiosulfonate spin label attaches rigidly and stereospecifically to Cys residues at i and i+4 positions along PLB's transmembrane helix, thus providing orientational resolution similar to that of TOAC, while being applicable to larger membrane proteins for which synthesis is impractical. Computational modeling and comparison with NMR data shows that these EPR experiments provide accurate information about helix tilt relative to the membrane normal, thus establishing a robust method for determining structural topology in large membrane proteins with a substantial advantage in sensitivity over NMR.
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Affiliation(s)
- Jesse E McCaffrey
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Zachary M James
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Bengt Svensson
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Benjamin P Binder
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | - David D Thomas
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA.
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Vostrikov VV, Mote KR, Verardi R, Veglia G. Structural dynamics and topology of phosphorylated phospholamban homopentamer reveal its role in the regulation of calcium transport. Structure 2013; 21:2119-30. [PMID: 24207128 DOI: 10.1016/j.str.2013.09.008] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Revised: 09/07/2013] [Accepted: 09/11/2013] [Indexed: 01/25/2023]
Abstract
Phospholamban (PLN) inhibits the sarco(endo)plasmic reticulum Ca²⁺-ATPase (SERCA), thereby regulating cardiac diastole. In membranes, PLN assembles into homopentamers that in both the phosphorylated and nonphosphorylated states have been proposed to form ion-selective channels. Here, we determined the structure of the phosphorylated pentamer using a combination of solution and solid-state nuclear magnetic resonance methods. We found that the pinwheel architecture of the homopentamer is preserved upon phosphorylation, with each monomer having an L-shaped conformation. The TM domains form a hydrophobic pore approximately 24 Å long and 2 Å in diameter, which is inconsistent with canonical Ca²⁺-selective channels. Phosphorylation, however, enhances the conformational dynamics of the cytoplasmic region of PLN, causing partial unwinding of the amphipathic helix. We propose that PLN oligomers act as storage for active monomers, keeping SERCA function within a physiological window.
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Affiliation(s)
- Vitaly V Vostrikov
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
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Mote KR, Gopinath T, Veglia G. Determination of structural topology of a membrane protein in lipid bilayers using polarization optimized experiments (POE) for static and MAS solid state NMR spectroscopy. JOURNAL OF BIOMOLECULAR NMR 2013; 57:91-102. [PMID: 23963722 PMCID: PMC3883141 DOI: 10.1007/s10858-013-9766-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Accepted: 07/26/2013] [Indexed: 05/11/2023]
Abstract
The low sensitivity inherent to both the static and magic angle spinning techniques of solid-state NMR (ssNMR) spectroscopy has thus far limited the routine application of multidimensional experiments to determine the structure of membrane proteins in lipid bilayers. Here, we demonstrate the advantage of using a recently developed class of experiments, polarization optimized experiments, for both static and MAS spectroscopy to achieve higher sensitivity and substantial time-savings for 2D and 3D experiments. We used sarcolipin, a single pass membrane protein, reconstituted in oriented bicelles (for oriented ssNMR) and multilamellar vesicles (for MAS ssNMR) as a benchmark. The restraints derived by these experiments are then combined into a hybrid energy function to allow simultaneous determination of structure and topology. The resulting structural ensemble converged to a helical conformation with a backbone RMSD ~0.44 Å, a tilt angle of 24° ± 1°, and an azimuthal angle of 55° ± 6°. This work represents a crucial first step toward obtaining high-resolution structures of large membrane proteins using combined multidimensional oriented solid-state NMR and magic angle spinning solid-state NMR.
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Affiliation(s)
- Kaustubh R. Mote
- Department of Chemistry University of Minnesota, Minneapolis, MN 55455, USA
| | - T. Gopinath
- Department of Biochemistry, Molecular Biology & Biophysics University of Minnesota, Minneapolis, MN 55455, USA
| | - Gianluigi Veglia
- Department of Chemistry University of Minnesota, Minneapolis, MN 55455, USA
- Department of Biochemistry, Molecular Biology & Biophysics University of Minnesota, Minneapolis, MN 55455, USA
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Tuning the structural coupling between the transmembrane and cytoplasmic domains of phospholamban to control sarcoplasmic reticulum Ca(2+)-ATPase (SERCA) function. J Muscle Res Cell Motil 2012; 33:485-92. [PMID: 22971924 DOI: 10.1007/s10974-012-9319-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Accepted: 08/18/2012] [Indexed: 12/15/2022]
Abstract
Phospholamban (PLN) is the endogenous inhibitor of the sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA), the integral membrane enzyme responsible for 70 % of the removal of Ca(2+) from the cytosol, inducing cardiac muscle relaxation in humans. Dysfunctions in SERCA:PLN interactions have been implicated as having a critical role in cardiac disease, and targeting Ca(2+) transport has been demonstrated to be a promising avenue in treating conditions of heart failure. Here, we designed a series of new mutants able to tune SERCA function, targeting the loop sequence that connects the transmembrane and cytoplasmic helices of PLN. We found that a variable degree of loss of inhibition mutants is attainable by engineering glycine mutations along PLN's loop domain. Remarkably, a double glycine mutation results in a complete loss-of-function mutant, fully mimicking the phosphorylated state of PLN. Using nuclear magnetic resonance spectroscopy, we rationalized the effects of these mutations in terms of entropic control on PLN function, whose inhibitory function can be modulated by increasing its conformational dynamics. However, if PLN mutations go past a threshold set by the phosphorylated state, they break the structural coupling between the transmembrane and cytoplasmic domains, resulting in a species that behaves as the inhibitory transmembrane domain alone. These studies provide new potential candidates for gene therapy to reverse the effects of heart failure.
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Gopinath T, Mote KR, Veglia G. Proton evolved local field solid-state nuclear magnetic resonance using Hadamard encoding: theory and application to membrane proteins. J Chem Phys 2011; 135:074503. [PMID: 21861572 DOI: 10.1063/1.3622604] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
NMR anisotropic parameters such as dipolar couplings and chemical shifts are central to structure and orientation determination of aligned membrane proteins and liquid crystals. Among the separated local field experiments, the proton evolved local field (PELF) scheme is particularly suitable to measure dynamically averaged dipolar couplings and give information on local molecular motions. However, the PELF experiment requires the acquisition of several 2D datasets at different mixing times to optimize the sensitivity for the complete range of dipolar couplings of the resonances in the spectrum. Here, we propose a new PELF experiment that takes the advantage of the Hadamard encoding (HE) to obtain higher sensitivity for a broad range of dipolar couplings using a single 2D experiment. The HE scheme is obtained by selecting the spin operators with phase switching of hard pulses. This approach enables one to detect four spin operators, simultaneously, which can be processed into two 2D spectra covering a broader range of dipolar couplings. The advantages of the new approach are illustrated for a U-(15)N NAL single crystal and the U-(15)N labeled single-pass membrane protein sarcolipin reconstituted in oriented lipid bicelles. The HE-PELF scheme can be implemented in other multidimensional experiments to speed up the characterization of the structure and dynamics of oriented membrane proteins and liquid crystalline samples.
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Affiliation(s)
- T Gopinath
- Department of Biochemistry, Molecular Biology, and Biophysics, Minneapolis, Minnesota 55455, USA
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Mote KR, Gopinath T, Traaseth NJ, Kitchen J, Gor'kov PL, Brey WW, Veglia G. Multidimensional oriented solid-state NMR experiments enable the sequential assignment of uniformly 15N labeled integral membrane proteins in magnetically aligned lipid bilayers. JOURNAL OF BIOMOLECULAR NMR 2011; 51:339-346. [PMID: 21976256 DOI: 10.1007/s10858-011-9571-8] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2011] [Accepted: 08/11/2011] [Indexed: 05/31/2023]
Abstract
Oriented solid-state NMR is the most direct methodology to obtain the orientation of membrane proteins with respect to the lipid bilayer. The method consists of measuring (1)H-(15)N dipolar couplings (DC) and (15)N anisotropic chemical shifts (CSA) for membrane proteins that are uniformly aligned with respect to the membrane bilayer. A significant advantage of this approach is that tilt and azimuthal (rotational) angles of the protein domains can be directly derived from analytical expression of DC and CSA values, or, alternatively, obtained by refining protein structures using these values as harmonic restraints in simulated annealing calculations. The Achilles' heel of this approach is the lack of suitable experiments for sequential assignment of the amide resonances. In this Article, we present a new pulse sequence that integrates proton driven spin diffusion (PDSD) with sensitivity-enhanced PISEMA in a 3D experiment ([(1)H,(15)N]-SE-PISEMA-PDSD). The incorporation of 2D (15)N/(15)N spin diffusion experiments into this new 3D experiment leads to the complete and unambiguous assignment of the (15)N resonances. The feasibility of this approach is demonstrated for the membrane protein sarcolipin reconstituted in magnetically aligned lipid bicelles. Taken with low electric field probe technology, this approach will propel the determination of sequential assignment as well as structure and topology of larger integral membrane proteins in aligned lipid bilayers.
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Affiliation(s)
- Kaustubh R Mote
- Department of Chemistry, University of Minnesota, Minneapolis, MN 55455-0431, USA
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Myint W, Gong Q, Ahn J, Ishima R. Characterization of sarcoplasmic reticulum Ca2+ ATPase nucleotide binding domain mutants using NMR spectroscopy. Biochem Biophys Res Commun 2010; 405:19-23. [PMID: 21187073 DOI: 10.1016/j.bbrc.2010.12.094] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2010] [Accepted: 12/20/2010] [Indexed: 11/25/2022]
Abstract
Sarcoplasmic reticulum Ca(2+) ATPase (SERCA) is essential for muscle function by transporting Ca(2+) from the cytosol into the sarcoplasmic reticulum through ATP hydrolysis. In this report, the effects of substitution mutations on the isolated SERCA-nucleotide binding domain (SERCA-N) were studied using NMR. (15)N-(1)H HSQC spectra of substitution mutants at the nucleotide binding site, T441A, R560V, and C561A, showed chemical shift changes, primarily in residues adjacent to the mutation sites, indicating only local effects. Further, the patterns of chemical shift changes upon AMP-PNP binding to these mutants were similar to that of the wild type SERCA-N (WT). In contrast to these nucleotide binding site mutants, a mutant found in patients with Darier's disease, E412G, showed small but significant chemical shift changes throughout the protein and rapid precipitation. However, the AMP-PNP dissociation constant (∼2.5 mM) was similar to that of WT (∼3.8 mM). These results indicate that the E412G mutant retains its catalytic activity but most likely reduces its stability. Our findings provide molecular insight into previous clinical, physiological, and biochemical observations.
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Affiliation(s)
- Wazo Myint
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260, USA
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