1
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Dixit G, Stowe RB, Bates A, Jaycox CK, Escobar JR, Harding BD, Drew DL, New CP, Sahu ID, Edelmann RE, Dabney-Smith C, Sanders CR, Lorigan GA. Purification and membrane interactions of human KCNQ1 100-370 potassium ion channel. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2022; 1864:184010. [PMID: 35870481 DOI: 10.1016/j.bbamem.2022.184010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Revised: 07/12/2022] [Accepted: 07/14/2022] [Indexed: 06/15/2023]
Abstract
KCNQ1 (Kv7.1 or KvLQT1) is a voltage-gated potassium ion channel that is involved in the ventricular repolarization following an action potential in the heart. It forms a complex with KCNE1 in the heart and is the pore forming subunit of slow delayed rectifier potassium current (Iks). Mutations in KCNQ1, leading to a dysfunctional channel or loss of activity have been implicated in a cardiac disorder, long QT syndrome. In this study, we report the overexpression, purification, biochemical characterization of human KCNQ1100-370, and lipid bilayer dynamics upon interaction with KCNQ1100-370. The recombinant human KCNQ1 was expressed in Escherichia coli and purified into n-dodecylphosphocholine (DPC) micelles. The purified KCNQ1100-370 was biochemically characterized by SDS-PAGE electrophoresis, western blot and nano-LC-MS/MS to confirm the identity of the protein. Circular dichroism (CD) spectroscopy was utilized to confirm the secondary structure of purified protein in vesicles. Furthermore, 31P and 2H solid-state NMR spectroscopy in DPPC/POPC/POPG vesicles (MLVs) indicated a direct interaction between KCNQ100-370 and the phospholipid head groups. Finally, a visual inspection of KCNQ1100-370 incorporated into MLVs was confirmed by transmission electron microscopy (TEM). The findings of this study provide avenues for future structural studies of the human KCNQ1 ion channel to have an in depth understanding of its structure-function relationship.
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Affiliation(s)
- Gunjan Dixit
- Department of Chemistry and Biochemistry, Miami University, 651 E. High Street, Oxford, OH 45056, USA; Cell, Molecular and Structural Biology Program, Department of Chemistry & Biochemistry, Miami University, Oxford, OH 45056, USA
| | - Rebecca B Stowe
- Department of Chemistry and Biochemistry, Miami University, 651 E. High Street, Oxford, OH 45056, USA
| | - Alison Bates
- Department of Chemistry and Biochemistry, Miami University, 651 E. High Street, Oxford, OH 45056, USA
| | - Colleen K Jaycox
- Department of Chemistry and Biochemistry, Miami University, 651 E. High Street, Oxford, OH 45056, USA
| | - Jorge R Escobar
- Department of Chemistry and Biochemistry, Miami University, 651 E. High Street, Oxford, OH 45056, USA; Cell, Molecular and Structural Biology Program, Department of Chemistry & Biochemistry, Miami University, Oxford, OH 45056, USA
| | - Benjamin D Harding
- Department of Chemistry and Biochemistry, Miami University, 651 E. High Street, Oxford, OH 45056, USA
| | - Daniel L Drew
- Department of Chemistry and Biochemistry, Miami University, 651 E. High Street, Oxford, OH 45056, USA
| | - Christopher P New
- Department of Chemistry and Biochemistry, Miami University, 651 E. High Street, Oxford, OH 45056, USA; Cell, Molecular and Structural Biology Program, Department of Chemistry & Biochemistry, Miami University, Oxford, OH 45056, USA
| | - Indra D Sahu
- Department of Chemistry and Biochemistry, Miami University, 651 E. High Street, Oxford, OH 45056, USA
| | - Richard E Edelmann
- Center for Advanced Microscopy and Imaging, Miami University, Oxford, OH 45056, USA
| | - Carole Dabney-Smith
- Department of Chemistry and Biochemistry, Miami University, 651 E. High Street, Oxford, OH 45056, USA; Cell, Molecular and Structural Biology Program, Department of Chemistry & Biochemistry, Miami University, Oxford, OH 45056, USA
| | - Charles R Sanders
- Department of Biochemistry and Center for Structural Biology, Vanderbilt University, Nashville, TN 37240, USA
| | - Gary A Lorigan
- Department of Chemistry and Biochemistry, Miami University, 651 E. High Street, Oxford, OH 45056, USA; Cell, Molecular and Structural Biology Program, Department of Chemistry & Biochemistry, Miami University, Oxford, OH 45056, USA.
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2
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Abstract
In the last two decades, solid-state nuclear magnetic resonance (ssNMR) spectroscopy has transformed from a spectroscopic technique investigating small molecules and industrial polymers to a potent tool decrypting structure and underlying dynamics of complex biological systems, such as membrane proteins, fibrils, and assemblies, in near-physiological environments and temperatures. This transformation can be ascribed to improvements in hardware design, sample preparation, pulsed methods, isotope labeling strategies, resolution, and sensitivity. The fundamental engagement between nuclear spins and radio-frequency pulses in the presence of a strong static magnetic field is identical between solution and ssNMR, but the experimental procedures vastly differ because of the absence of molecular tumbling in solids. This review discusses routinely employed state-of-the-art static and MAS pulsed NMR methods relevant for biological samples with rotational correlation times exceeding 100's of nanoseconds. Recent developments in signal filtering approaches, proton methodologies, and multiple acquisition techniques to boost sensitivity and speed up data acquisition at fast MAS are also discussed. Several examples of protein structures (globular, membrane, fibrils, and assemblies) solved with ssNMR spectroscopy have been considered. We also discuss integrated approaches to structurally characterize challenging biological systems and some newly emanating subdisciplines in ssNMR spectroscopy.
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Affiliation(s)
- Sahil Ahlawat
- Tata Institute of Fundamental Research Hyderabad, Survey No. 36/P Gopanpally, Serilingampally, Ranga Reddy District, Hyderabad 500046, Telangana, India
| | - Kaustubh R Mote
- Tata Institute of Fundamental Research Hyderabad, Survey No. 36/P Gopanpally, Serilingampally, Ranga Reddy District, Hyderabad 500046, Telangana, India
| | - Nils-Alexander Lakomek
- University of Düsseldorf, Institute for Physical Biology, Universitätsstraße 1, 40225 Düsseldorf, Germany
| | - Vipin Agarwal
- Tata Institute of Fundamental Research Hyderabad, Survey No. 36/P Gopanpally, Serilingampally, Ranga Reddy District, Hyderabad 500046, Telangana, India
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3
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Qin J, Zhang J, Lin L, Haji-Ghassemi O, Lin Z, Woycechowsky KJ, Van Petegem F, Zhang Y, Yuchi Z. Structures of PKA-phospholamban complexes reveal a mechanism of familial dilated cardiomyopathy. eLife 2022; 11:75346. [PMID: 35297759 PMCID: PMC8970585 DOI: 10.7554/elife.75346] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Accepted: 03/16/2022] [Indexed: 01/07/2023] Open
Abstract
Several mutations identified in phospholamban (PLN) have been linked to familial dilated cardiomyopathy (DCM) and heart failure, yet the underlying molecular mechanism remains controversial. PLN interacts with sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) and regulates calcium uptake, which is modulated by the protein kinase A (PKA)-dependent phosphorylation of PLN during the fight-or-flight response. Here, we present the crystal structures of the catalytic domain of mouse PKA in complex with wild-type and DCM-mutant PLNs. Our structures, combined with the results from other biophysical and biochemical assays, reveal a common disease mechanism: the mutations in PLN reduce its phosphorylation level by changing its conformation and weakening its interactions with PKA. In addition, we demonstrate that another more ubiquitous SERCA-regulatory peptide, called another-regulin (ALN), shares a similar mechanism mediated by PKA in regulating SERCA activity.
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Affiliation(s)
- Juan Qin
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency; Collaborative Innovation Center of Chemical Science and Engineering; School of Pharmaceutical Science and Technology, Tianjin UniversityTianjinChina
| | - Jingfeng Zhang
- Wuhan Institute of Physics and Mathematics, Chinese Academy of SciencesWuhanChina
| | - Lianyun Lin
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency; Collaborative Innovation Center of Chemical Science and Engineering; School of Pharmaceutical Science and Technology, Tianjin UniversityTianjinChina
| | - Omid Haji-Ghassemi
- Department of Biochemistry and Molecular Biology, The Life Sciences Centre, University of British ColumbiaVancouverCanada
| | - Zhi Lin
- School of Life Sciences, Tianjin UniversityTianjinChina
| | - Kenneth J Woycechowsky
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency; Collaborative Innovation Center of Chemical Science and Engineering; School of Pharmaceutical Science and Technology, Tianjin UniversityTianjinChina
| | - Filip Van Petegem
- Department of Biochemistry and Molecular Biology, The Life Sciences Centre, University of British ColumbiaVancouverCanada
| | - Yan Zhang
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency; Collaborative Innovation Center of Chemical Science and Engineering; School of Pharmaceutical Science and Technology, Tianjin UniversityTianjinChina
| | - Zhiguang Yuchi
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency; Collaborative Innovation Center of Chemical Science and Engineering; School of Pharmaceutical Science and Technology, Tianjin UniversityTianjinChina,Department of Molecular Pharmacology, Tianjin Medical University Cancer Institute & Hospital; National Clinical Research Center for Cancer; Key Laboratory of Cancer Prevention and Therapy, Tianjin; Tianjin’s Clinical Research Center for CancerTianjinChina
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4
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Drew DL, Butcher B, Sahu ID, Ahammad T, Dixit G, Lorigan GA. Active S 2168 and inactive S 21IRS pinholin interact differently with the lipid bilayer: A 31P and 2H solid state NMR study. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183257. [PMID: 32147355 DOI: 10.1016/j.bbamem.2020.183257] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 02/28/2020] [Accepted: 03/02/2020] [Indexed: 01/02/2023]
Abstract
Pinholins are a family of lytic membrane proteins responsible for the lysis of the cytosolic membrane in host cells of double stranded DNA bacteriophages. Protein-lipid interactions have been shown to influence membrane protein topology as well as its function. This work investigated the interactions of pinholin with the phospholipid bilayer while in active and inactive confirmations to elucidate the different interactions the two forms have with the bilayer. Pinholin incorporated into deuterated DMPC-d54 lipid bilayers, along with 31P and 2H solid state NMR (SS-NMR) spectroscopy were used to probe the protein-lipid interactions with the phosphorus head group at the surface of the bilayer while interactions with the 2H nuclei were used to study the hydrophobic core. A comparison of the 31P chemical shift anisotropy (CSA) values of the active S2168 pinholin and inactive S21IRS pinholin indicated stronger head group interactions for the pinholin in its active form when compared to that of the inactive form supporting the model of a partially externalized peripheral transmembrane domain (TMD) of the active S2168 instead of complete externalized TMD1 as suggested by Ahammad et al. JPC B 2019. The 2H quadrupolar splitting analysis showed a decrease in spectral width for both forms of the pinholin when compared to the empty bilayers at all temperatures. In this case the decrease in the spectral width of the inactive S21IRS form of the pinholin showed stronger interactions with the acyl chains of the bilayer. The presence of the inactive form's additional TMD within the membrane was supported by the loss of peak resolution observed in the 2H NMR spectra.
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Affiliation(s)
- Daniel L Drew
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA.
| | - Brandon Butcher
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA.
| | - Indra D Sahu
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA; Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA.
| | - Tanbir Ahammad
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA.
| | - Gunjan Dixit
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA.
| | - Gary A Lorigan
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA.
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5
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Larsen EK, Weber DK, Wang S, Gopinath T, Blackwell DJ, Dalton MP, Robia SL, Gao J, Veglia G. Intrinsically disordered HAX-1 regulates Ca 2+ cycling by interacting with lipid membranes and the phospholamban cytoplasmic region. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2020; 1862:183034. [PMID: 31400305 PMCID: PMC6899184 DOI: 10.1016/j.bbamem.2019.183034] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Revised: 07/09/2019] [Accepted: 07/30/2019] [Indexed: 01/14/2023]
Abstract
Hematopoietic-substrate-1 associated protein X-1 (HAX-1) is a 279 amino acid protein expressed ubiquitously. In cardiac muscle, HAX-1 was found to modulate the sarcoendoplasmic reticulum calcium ATPase (SERCA) by shifting its apparent Ca2+ affinity (pCa). It has been hypothesized that HAX-1 binds phospholamban (PLN), enhancing its inhibitory function on SERCA. HAX-1 effects are reversed by cAMP-dependent protein kinase A that phosphorylates PLN at Ser16. To date, the molecular mechanisms for HAX-1 regulation of the SERCA/PLN complex are still unknown. Using enzymatic, in cell assays, circular dichroism, and NMR spectroscopy, we found that in the absence of a binding partner HAX-1 is essentially disordered and adopts a partial secondary structure upon interaction with lipid membranes. Also, HAX-1 interacts with the cytoplasmic region of monomeric and pentameric PLN as detected by NMR and in cell FRET assays, respectively. We propose that the regulation of the SERCA/PLN complex by HAX-1 is mediated by its interactions with lipid membranes, adding another layer of control in Ca2+ homeostatic balance in the heart muscle.
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Affiliation(s)
- Erik K Larsen
- Department of Chemistry, University of Minnesota, Minneapolis, MN 55455, USA
| | - Daniel K Weber
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Songlin Wang
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Tata Gopinath
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | | | - Michael P Dalton
- Department of Physiology, Loyola University, Maywood, IL 60153, USA
| | - Seth L Robia
- Department of Physiology, Loyola University, Maywood, IL 60153, USA
| | - Jiali Gao
- Department of Chemistry, University of Minnesota, Minneapolis, MN 55455, USA; School of Chemical Biology and Technology, Beijing University Graduate School, Shenzhen 518055, China
| | - Gianluigi Veglia
- Department of Chemistry, University of Minnesota, Minneapolis, MN 55455, USA; Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA.
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6
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Newly Discovered Micropeptide Regulators of SERCA Form Oligomers but Bind to the Pump as Monomers. J Mol Biol 2019; 431:4429-4443. [PMID: 31449798 DOI: 10.1016/j.jmb.2019.07.037] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Revised: 07/26/2019] [Accepted: 07/31/2019] [Indexed: 12/22/2022]
Abstract
The recently-discovered single-span transmembrane proteins endoregulin (ELN), dwarf open reading frame (DWORF), myoregulin (MLN), and another-regulin (ALN) are reported to bind to the SERCA calcium pump in a manner similar to that of known regulators of SERCA activity, phospholamban (PLB) and sarcolipin (SLN). To determine how micropeptide assembly into oligomers affects the availability of the micropeptide to bind to SERCA in a regulatory complex, we used co-immunoprecipitation and fluorescence resonance energy transfer (FRET) to quantify micropeptide oligomerization and SERCA-binding. Micropeptides formed avid homo-oligomers with high-order stoichiometry (n > 2 protomers per homo-oligomer), but it was the monomeric form of all micropeptides that interacted with SERCA. In view of these two alternative binding interactions, we evaluated the possibility that oligomerization occurs at the expense of SERCA-binding. However, even the most avidly oligomeric micropeptide species still showed robust FRET with SERCA, and there was a surprising positive correlation between oligomerization affinity and SERCA-binding. This comparison of micropeptide family members suggests that the same structural determinants that support oligomerization are also important for binding to SERCA. Moreover, the unique oligomerization/SERCA-binding profile of DWORF is in harmony with its distinct role as a PLB-competing SERCA activator, in contrast to the inhibitory function of the other SERCA-binding micropeptides.
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7
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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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8
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Dixit G, Sahu ID, Reynolds WD, Wadsworth TM, Harding BD, Jaycox CK, Dabney-Smith C, Sanders CR, Lorigan GA. Probing the Dynamics and Structural Topology of the Reconstituted Human KCNQ1 Voltage Sensor Domain (Q1-VSD) in Lipid Bilayers Using Electron Paramagnetic Resonance Spectroscopy. Biochemistry 2019; 58:965-973. [PMID: 30620191 DOI: 10.1021/acs.biochem.8b01042] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
KCNQ1 (Kv7.1 or KvLQT1) is a potassium ion channel protein found in the heart, ear, and other tissues. In complex with the KCNE1 accessory protein, it plays a role during the repolarization phase of the cardiac action potential. Mutations in the channel have been associated with several diseases, including congenital deafness and long QT syndrome. Nuclear magnetic resonance (NMR) structural studies in detergent micelles and a cryo-electron microscopy structure of KCNQ1 from Xenopus laevis have shown that the voltage sensor domain (Q1-VSD) of the channel has four transmembrane helices, S1-S4, being overall structurally similar with other VSDs. In this study, we describe a reliable method for the reconstitution of Q1-VSD into (POPC/POPG) lipid bilayer vesicles. Site-directed spin labeling electron paramagnetic resonance spectroscopy was used to probe the structural dynamics and topology of several residues of Q1-VSD in POPC/POPG lipid bilayer vesicles. Several mutants were probed to determine their location and corresponding immersion depth (in angstroms) with respect to the membrane. The dynamics of the bilayer vesicles upon incorporation of Q1-VSD were studied using 31P solid-state NMR spectroscopy by varying the protein:lipid molar ratios confirming the interaction of the protein with the bilayer vesicles. Circular dichroism spectroscopic data showed that the α-helical content of Q1-VSD is higher for the protein reconstituted in vesicles than in previous studies using DPC detergent micelles. This study provides insight into the structural topology and dynamics of Q1-VSD reconstituted in a lipid bilayer environment, forming the basis for more advanced structural and functional studies.
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Affiliation(s)
- Gunjan Dixit
- Department of Chemistry and Biochemistry , Miami University , 651 East High Street , Oxford , Ohio 45056 , United States
| | - Indra D Sahu
- Department of Chemistry and Biochemistry , Miami University , 651 East High Street , Oxford , Ohio 45056 , United States
| | - Warren D Reynolds
- Department of Chemistry and Biochemistry , Miami University , 651 East High Street , Oxford , Ohio 45056 , United States
| | - Tessa M Wadsworth
- Department of Chemistry and Biochemistry , Miami University , 651 East High Street , Oxford , Ohio 45056 , United States
| | - Benjamin D Harding
- Department of Chemistry and Biochemistry , Miami University , 651 East High Street , Oxford , Ohio 45056 , United States
| | - Colleen K Jaycox
- Department of Chemistry and Biochemistry , Miami University , 651 East High Street , Oxford , Ohio 45056 , United States
| | - Carole Dabney-Smith
- Department of Chemistry and Biochemistry , Miami University , 651 East High Street , Oxford , Ohio 45056 , United States
| | - Charles R Sanders
- Department of Biochemistry and Center for Structural Biology , Vanderbilt University , Nashville , Tennessee 37240 , United States
| | - Gary A Lorigan
- Department of Chemistry and Biochemistry , Miami University , 651 East High Street , Oxford , Ohio 45056 , United States
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9
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Drew DL, Ahammad T, Serafin RA, Butcher BJ, Clowes KR, Drake Z, Sahu ID, McCarrick RM, Lorigan GA. Solid phase synthesis and spectroscopic characterization of the active and inactive forms of bacteriophage S 21 pinholin protein. Anal Biochem 2018; 567:14-20. [PMID: 30528914 DOI: 10.1016/j.ab.2018.12.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Revised: 11/29/2018] [Accepted: 12/03/2018] [Indexed: 01/06/2023]
Abstract
The mechanism for the lysis pathway of double-stranded DNA bacteriophages involves a small hole-forming class of membrane proteins, the holins. This study focuses on a poorly characterized class of holins, the pinholin, of which the S21 protein of phage ϕ21 is the prototype. Here we report the first in vitro synthesis of the wildtype form of the S21 pinholin, S2168, and negative-dominant mutant form, S21IRS, both prepared using solid phase peptide synthesis and studied using biophysical techniques. Both forms of the pinholin were labeled with a nitroxide spin label and successfully incorporated into both bicelles and multilamellar vesicles which are membrane mimetic systems. Circular dichroism revealed the two forms were both >80% alpha helical, in agreement with the predictions based on the literature. The molar ellipticity ratio [θ]222/[θ]208 for both forms of the pinholin was 1.4, suggesting a coiled-coil tertiary structure in the bilayer consistent with the proposed oligomerization step in models for the mechanism of hole formation. 31P solid-state NMR spectroscopic data on pinholin indicate a strong interaction of both forms of the pinholin with the membrane headgroups. The 31P NMR data has an axially symmetric line shape which is consistent with lamellar phase proteoliposomes lipid mimetics.
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Affiliation(s)
- Daniel L Drew
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH, 45056, USA
| | - Tanbir Ahammad
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH, 45056, USA
| | - Rachel A Serafin
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH, 45056, USA
| | - Brandon J Butcher
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH, 45056, USA
| | - Katherine R Clowes
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH, 45056, USA
| | - Zachary Drake
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH, 45056, USA
| | - Indra D Sahu
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH, 45056, USA
| | - Robert M McCarrick
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH, 45056, USA
| | - Gary A Lorigan
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH, 45056, USA.
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10
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Chipot C, Dehez F, Schnell JR, Zitzmann N, Pebay-Peyroula E, Catoire LJ, Miroux B, Kunji ERS, Veglia G, Cross TA, Schanda P. Perturbations of Native Membrane Protein Structure in Alkyl Phosphocholine Detergents: A Critical Assessment of NMR and Biophysical Studies. Chem Rev 2018; 118:3559-3607. [PMID: 29488756 PMCID: PMC5896743 DOI: 10.1021/acs.chemrev.7b00570] [Citation(s) in RCA: 117] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Indexed: 12/25/2022]
Abstract
Membrane proteins perform a host of vital cellular functions. Deciphering the molecular mechanisms whereby they fulfill these functions requires detailed biophysical and structural investigations. Detergents have proven pivotal to extract the protein from its native surroundings. Yet, they provide a milieu that departs significantly from that of the biological membrane, to the extent that the structure, the dynamics, and the interactions of membrane proteins in detergents may considerably vary, as compared to the native environment. Understanding the impact of detergents on membrane proteins is, therefore, crucial to assess the biological relevance of results obtained in detergents. Here, we review the strengths and weaknesses of alkyl phosphocholines (or foscholines), the most widely used detergent in solution-NMR studies of membrane proteins. While this class of detergents is often successful for membrane protein solubilization, a growing list of examples points to destabilizing and denaturing properties, in particular for α-helical membrane proteins. Our comprehensive analysis stresses the importance of stringent controls when working with this class of detergents and when analyzing the structure and dynamics of membrane proteins in alkyl phosphocholine detergents.
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Affiliation(s)
- Christophe Chipot
- SRSMC, UMR 7019 Université de Lorraine CNRS, Vandoeuvre-les-Nancy F-54500, France
- Laboratoire
International Associé CNRS and University of Illinois at Urbana−Champaign, Vandoeuvre-les-Nancy F-54506, France
- Department
of Physics, University of Illinois at Urbana−Champaign, 1110 West Green Street, Urbana, Illinois 61801, United States
| | - François Dehez
- SRSMC, UMR 7019 Université de Lorraine CNRS, Vandoeuvre-les-Nancy F-54500, France
- Laboratoire
International Associé CNRS and University of Illinois at Urbana−Champaign, Vandoeuvre-les-Nancy F-54506, France
| | - Jason R. Schnell
- Department
of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom
| | - Nicole Zitzmann
- Department
of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom
| | | | - Laurent J. Catoire
- Laboratory
of Biology and Physico-Chemistry of Membrane Proteins, Institut de Biologie Physico-Chimique (IBPC), UMR
7099 CNRS, Paris 75005, France
- University
Paris Diderot, Paris 75005, France
- PSL
Research University, Paris 75005, France
| | - Bruno Miroux
- Laboratory
of Biology and Physico-Chemistry of Membrane Proteins, Institut de Biologie Physico-Chimique (IBPC), UMR
7099 CNRS, Paris 75005, France
- University
Paris Diderot, Paris 75005, France
- PSL
Research University, Paris 75005, France
| | - Edmund R. S. Kunji
- Medical
Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, United Kingdom
| | - Gianluigi Veglia
- Department
of Biochemistry, Molecular Biology, and Biophysics, and Department
of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Timothy A. Cross
- National
High Magnetic Field Laboratory, Florida
State University, Tallahassee, Florida 32310, United States
| | - Paul Schanda
- Université
Grenoble Alpes, CEA, CNRS, IBS, Grenoble F-38000, France
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11
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Zhang R, Sahu ID, Comer RG, Maltsev S, Dabney-Smith C, Lorigan GA. Probing the interaction of the potassium channel modulating KCNE1 in lipid bilayers via solid-state NMR spectroscopy. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2017; 55:754-758. [PMID: 28233402 PMCID: PMC5498220 DOI: 10.1002/mrc.4589] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Revised: 02/09/2017] [Accepted: 02/19/2017] [Indexed: 06/06/2023]
Abstract
KCNE1 is known to modulate the voltage-gated potassium channel α subunit KCNQ1 to generate slowly activating potassium currents. This potassium channel is essential for the cardiac action potential that mediates a heartbeat as well as the potassium ion homeostasis in the inner ear. Therefore, it is important to know the structure and dynamics of KCNE1 to better understand its modulatory role. Previously, the Sanders group solved the three-dimensional structure of KCNE1 in LMPG micelles, which yielded a better understanding of this KCNQ1/KCNE1 channel activity. However, research in the Lorigan group showed different structural properties of KCNE1 when incorporated into POPC/POPG lipid bilayers as opposed to LMPG micelles. It is hence necessary to study the structure of KCNE1 in a more native-like environment such as multi-lamellar vesicles. In this study, the dynamics of lipid bilayers upon incorporation of the membrane protein KCNE1 were investigated using 31 P solid-state nuclear magnetic resonance (NMR) spectroscopy. Specifically, the protein/lipid interaction was studied at varying molar ratios of protein to lipid content. The static 31 P NMR and T1 relaxation time were investigated. The 31 P NMR powder spectra indicated significant perturbations of KCNE1 on the phospholipid headgroups of multi-lamellar vesicles as shown from the changes in the 31 P spectral line shape and the chemical shift anisotropy line width. 31 P T1 relaxation times were shown to be reversely proportional to the molar ratios of KCNE1 incorporated. The 31 P NMR data clearly indicate that KCNE1 interacts with the membrane. Copyright © 2017 John Wiley & Sons, Ltd.
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Affiliation(s)
- Rongfu Zhang
- Cell, Molecular, and Structural Biology Graduate Program, Miami University, Oxford, OH 45056
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056
| | - Indra D. Sahu
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056
| | - Raven G. Comer
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056
| | - Sergey Maltsev
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056
| | - Carole Dabney-Smith
- Cell, Molecular, and Structural Biology Graduate Program, Miami University, Oxford, OH 45056
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056
| | - Gary A. Lorigan
- Cell, Molecular, and Structural Biology Graduate Program, Miami University, Oxford, OH 45056
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056
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12
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Sanz-Hernández M, Vostrikov VV, Veglia G, De Simone A. Accurate Determination of Conformational Transitions in Oligomeric Membrane Proteins. Sci Rep 2016; 6:23063. [PMID: 26975211 PMCID: PMC4791661 DOI: 10.1038/srep23063] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Accepted: 02/25/2016] [Indexed: 12/27/2022] Open
Abstract
The structural dynamics governing collective motions in oligomeric membrane proteins play key roles in vital biomolecular processes at cellular membranes. In this study, we present a structural refinement approach that combines solid-state NMR experiments and molecular simulations to accurately describe concerted conformational transitions identifying the overall structural, dynamical, and topological states of oligomeric membrane proteins. The accuracy of the structural ensembles generated with this method is shown to reach the statistical error limit, and is further demonstrated by correctly reproducing orthogonal NMR data. We demonstrate the accuracy of this approach by characterising the pentameric state of phospholamban, a key player in the regulation of calcium uptake in the sarcoplasmic reticulum, and by probing its dynamical activation upon phosphorylation. Our results underline the importance of using an ensemble approach to characterise the conformational transitions that are often responsible for the biological function of oligomeric membrane protein states.
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Affiliation(s)
- Máximo Sanz-Hernández
- Department of Life Sciences, Imperial College London, South Kensington, London, SW7 2AZ, UK
| | - Vitaly V. Vostrikov
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Gianluigi Veglia
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
- Department of Chemistry, University of Minnesota, Minneapolis, MN 55455, USA
| | - Alfonso De Simone
- Department of Life Sciences, Imperial College London, South Kensington, London, SW7 2AZ, UK
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13
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Ablorh NAD, Thomas DD. Phospholamban phosphorylation, mutation, and structural dynamics: a biophysical approach to understanding and treating cardiomyopathy. Biophys Rev 2015; 7:63-76. [PMID: 28509982 DOI: 10.1007/s12551-014-0157-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Accepted: 11/26/2014] [Indexed: 01/16/2023] Open
Abstract
We review the recent development of novel biochemical and spectroscopic methods to determine the site-specific phosphorylation, expression, mutation, and structural dynamics of phospholamban (PLB), in relation to its function (inhibition of the cardiac calcium pump, SERCA2a), with specific focus on cardiac physiology, pathology, and therapy. In the cardiomyocyte, SERCA2a actively transports Ca2+ into the sarcoplasmic reticulum (SR) during relaxation (diastole) to create the concentration gradient that drives the passive efflux of Ca2+ required for cardiac contraction (systole). Unphosphorylated PLB (U-PLB) inhibits SERCA2a, but phosphorylation at S16 and/or T17 (producing P-PLB) changes the structure of PLB to relieve SERCA2a inhibition. Because insufficient SERCA2a activity is a hallmark of heart failure, SERCA2a activation, by gene therapy (Andino et al. 2008; Fish et al. 2013; Hoshijima et al. 2002; Jessup et al. 2011) or drug therapy (Ferrandi et al. 2013; Huang 2013; Khan et al. 2009; Rocchetti et al. 2008; Zhang et al. 2012), is a widely sought goal for treatment of heart failure. This review describes rational approaches to this goal. Novel biophysical assays, using site-directed labeling and high-resolution spectroscopy, have been developed to resolve the structural states of SERCA2a-PLB complexes in vitro and in living cells. Novel biochemical assays, using synthetic standards and multidimensional immunofluorescence, have been developed to quantitate PLB expression and phosphorylation states in cells and human tissues. The biochemical and biophysical properties of U-PLB, P-PLB, and mutant PLB will ultimately resolve the mechanisms of loss of inhibition and gain of inhibition to guide therapeutic development. These assays will be powerful tools for investigating human tissue samples from the Sydney Heart Bank, for the purpose of analyzing and diagnosing specific disorders.
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Affiliation(s)
- Naa-Adjeley D Ablorh
- 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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14
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Maltsev S, Hudson SM, Sahu ID, Liu L, Lorigan GA. Solid-state NMR (31)P paramagnetic relaxation enhancement membrane protein immersion depth measurements. J Phys Chem B 2014; 118:4370-7. [PMID: 24689497 PMCID: PMC4002136 DOI: 10.1021/jp500267y] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Revised: 04/01/2014] [Indexed: 11/29/2022]
Abstract
Paramagnetic relaxation enhancement (PRE) is a widely used approach for measuring long-range distance constraints in biomolecular solution NMR spectroscopy. In this paper, we show that (31)P PRE solid-state NMR spectroscopy can be utilized to determine the immersion depth of spin-labeled membrane peptides and proteins. Changes in the (31)P NMR PRE times coupled with modeling studies can be used to describe the spin-label position/amino acid within the lipid bilayer and the corresponding helical tilt. This method provides valuable insight on protein-lipid interactions and membrane protein structural topology. Solid-state (31)P NMR data on the 23 amino acid α-helical nicotinic acetylcholine receptor nAChR M2δ transmembrane domain model peptide followed predicted behavior of (31)P PRE rates of the phospholipid headgroup as the spin-label moves from the membrane surface toward the center of the membrane. Residue 11 showed the smallest changes in (31)P PRE (center of the membrane), while residue 22 shows the largest (31)P PRE change (near the membrane surface), when compared to the diamagnetic control M2δ sample. This PRE SS-NMR technique can be used as a molecular ruler to measure membrane immersion depth.
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Affiliation(s)
- Sergey Maltsev
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio 45056, United States
| | - Stephen M. Hudson
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio 45056, United States
| | - Indra D. Sahu
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio 45056, United States
| | - Lishan Liu
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio 45056, United States
| | - Gary A. Lorigan
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio 45056, United States
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15
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Yu X, Lorigan GA. Secondary structure, backbone dynamics, and structural topology of phospholamban and its phosphorylated and Arg9Cys-mutated forms in phospholipid bilayers utilizing 13C and 15N solid-state NMR spectroscopy. J Phys Chem B 2014; 118:2124-33. [PMID: 24511878 PMCID: PMC3983341 DOI: 10.1021/jp500316s] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Phospholamban (PLB) is a membrane protein that regulates heart muscle relaxation rates via interactions with the sarcoplasmic reticulum Ca(2+) ATPase (SERCA). When PLB is phosphorylated or Arg9Cys (R9C) is mutated, inhibition of SERCA is relieved. (13)C and (15)N solid-state NMR spectroscopy is utilized to investigate conformational changes of PLB upon phosphorylation and R9C mutation. (13)C═O NMR spectra of the cytoplasmic domain reveal two α-helical structural components with population changes upon phosphorylation and R9C mutation. The appearance of an unstructured component is observed on domain Ib. (15)N NMR spectra indicate an increase in backbone dynamics of the cytoplasmic domain. Wild-type PLB (WT-PLB), Ser16-phosphorylated PLB (P-PLB), and R9C-mutated PLB (R9C-PLB) all have a very dynamic domain Ib, and the transmembrane domain has an immobile component. (15)N NMR spectra indicate that the cytoplasmic domain of R9C-PLB adopts an orientation similar to P-PLB and shifts away from the membrane surface. Domain Ib (Leu28) of P-PLB and R9C-PLB loses the alignment. The R9C-PLB adopts a conformation similar to P-PLB with a population shift to a more extended and disordered state. The NMR data suggest the more extended and disordered forms of PLB may relate to inhibition relief.
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Affiliation(s)
- Xueting Yu
- Department of Chemistry and Biochemistry, Miami University , Oxford, Ohio 45056, United States
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16
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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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17
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Zhang L, Liu L, Maltsev S, Lorigan GA, Dabney-Smith C. Investigating the interaction between peptides of the amphipathic helix of Hcf106 and the phospholipid bilayer by solid-state NMR spectroscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1838:413-8. [PMID: 24144541 DOI: 10.1016/j.bbamem.2013.10.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Revised: 10/01/2013] [Accepted: 10/04/2013] [Indexed: 12/15/2022]
Abstract
The chloroplast twin arginine translocation (cpTat) system transports highly folded precursor proteins into the thylakoid lumen using the protonmotive force as its only energy source. Hcf106, as one of the core components of the cpTat system, is part of the precursor receptor complex and functions in the initial precursor-binding step. Hcf106 is predicted to contain a single amino terminal transmembrane domain followed by a Pro-Gly hinge, a predicted amphipathic α-helix (APH), and a loosely structured carboxy terminus. Hcf106 has been shown biochemically to insert spontaneously into thylakoid membranes. To better understand the membrane active capabilities of Hcf106, we used solid-state NMR spectroscopy to investigate those properties of the APH. In this study, synthesized peptides of the predicted Hcf106 APH (amino acids 28-65) were incorporated at increasing mol.% into 1-palmitoyl-2-oleoyl-sn-glycero-phosphocholine (POPC) and POPC/MGDG (monogalactosyldiacylglycerol; mole ratio 85:15) multilamellar vesicles (MLVs) to probe the peptide-lipid interaction. Solid-state (31)P NMR and (2)H NMR spectroscopic experiments revealed that the peptide perturbs the headgroup and the acyl chain regions of phospholipids as indicated by changes in spectral lineshape, chemical shift anisotropy (CSA) line width, and (2)H order SCD parameters. In addition, the comparison between POPC MLVs and POPC/MGDG MLVs indicated that the lipid bilayer composition affected peptide perturbation of the lipids, and such perturbation appeared to be more intense in a system more closely mimicking a thylakoid membrane.
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Affiliation(s)
- Lei Zhang
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA
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18
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Allosteric regulation of SERCA by phosphorylation-mediated conformational shift of phospholamban. Proc Natl Acad Sci U S A 2013; 110:17338-43. [PMID: 24101520 DOI: 10.1073/pnas.1303006110] [Citation(s) in RCA: 102] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The membrane protein complex between the sarcoplasmic reticulum Ca(2+)-ATPase (SERCA) and phospholamban (PLN) controls Ca(2+) transport in cardiomyocytes, thereby modulating cardiac contractility. β-Adrenergic-stimulated phosphorylation of PLN at Ser-16 enhances SERCA activity via an unknown mechanism. Using solid-state nuclear magnetic resonance spectroscopy, we mapped the physical interactions between SERCA and both unphosphorylated and phosphorylated PLN in membrane bilayers. We found that the allosteric regulation of SERCA depends on the conformational equilibrium of PLN, whose cytoplasmic regulatory domain interconverts between three different states: a ground T state (helical and membrane associated), an excited R state (unfolded and membrane detached), and a B state (extended and enzyme-bound), which is noninhibitory. Phosphorylation at Ser-16 of PLN shifts the populations toward the B state, increasing SERCA activity. We conclude that PLN's conformational equilibrium is central to maintain SERCA's apparent Ca(2+) affinity within a physiological window. This model represents a paradigm shift in our understanding of SERCA regulation by posttranslational phosphorylation and suggests strategies for designing innovative therapeutic approaches to enhance cardiac muscle contractility.
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19
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Zhang L, Liu L, Maltsev S, Lorigan GA, Dabney-Smith C. Solid-state NMR investigations of peptide–lipid interactions of the transmembrane domain of a plant-derived protein, Hcf106. Chem Phys Lipids 2013; 175-176:123-30. [DOI: 10.1016/j.chemphyslip.2013.09.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Revised: 09/16/2013] [Accepted: 09/17/2013] [Indexed: 02/02/2023]
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20
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Yu X, Lorigan GA. Probing the interaction of Arg9Cys mutated phospholamban with phospholipid bilayers by solid-state NMR spectroscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1828:2444-9. [PMID: 23850636 DOI: 10.1016/j.bbamem.2013.07.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Revised: 06/10/2013] [Accepted: 07/01/2013] [Indexed: 01/05/2023]
Abstract
Phospholamban (PLB) is a 52 amino acid integral membrane protein that interacts with the sarcoplasmic reticulum Ca(2+) ATPase (SERCA) and helps to regulate Ca(2+) flow. PLB inhibits SERCA impairing Ca(2+) translocation. The inhibition can be relieved upon phosphorylation of PLB. The Arg9 to Cys (R9C) mutation is a loss of function mutation with reduced inhibitory potency. The effect R9C PLB has on the membrane surface and the hydrophobic region dynamics was investigated by (31)P and (2)H solid-state NMR spectroscopy in multilamellar vesicles (MLVs). The (31)P NMR spectra indicate that, like the phosphorylated PLB (P-PLB), the mutated R9C-PLB protein has significantly less interaction with the lipid bilayer headgroup when compared to wild-type PLB (WT-PLB). Similar to P-PLB, R9C-PLB slightly decreases (31)P T1 values in the lipid headgroup region. (2)H SCD order parameters of (2)H nuclei along the lipid acyl chain decrease less dramatically for R9C-PLB and P-PLB when compared to WT-PLB. The results suggest that R9C-PLB interacts less with the membrane surface and hydrophobic region than WT-PLB. Detachment of the cytoplasmic domain of R9C-PLB from the membrane surface could be related to its loss of function.
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Affiliation(s)
- Xueting Yu
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA
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21
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Marbella LE, Cho HS, Spence MM. Observing the translocation of a mitochondria-penetrating peptide with solid-state NMR. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1828:1674-82. [PMID: 23567916 DOI: 10.1016/j.bbamem.2013.03.027] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2013] [Revised: 03/25/2013] [Accepted: 03/29/2013] [Indexed: 12/18/2022]
Abstract
A new class of penetrating peptides that can target the mitochondria with high specificity was recently discovered. In this work, we developed a model inner mitochondrial membrane, equipped with a transmembrane gradient, suitable for solid-state NMR experiments. Using solid-state NMR, we observed a mitochondria-penetrating peptide interacting with the model inner mitochondrial membrane to gain insight into the mechanism of translocation. The paramagnetic relaxation effect due to Mn(2+) ions on (13)C magic angle spinning NMR was used to measure the insertion depth of the peptide and its distribution in each monolayer of the membrane. We found that at low peptide concentration the peptide binds to the outer leaflet and at high concentration, it crosses the hydrophobic bilayer core and is distributed in both leaflets. In both concentration regimes, the peptide binds at the C2 position on the lipid acyl chain. The mitochondria-penetrating peptide crossed to the inner leaflet of the model membranes without disrupting the lamellarity. These results provide evidence that supports the electroporation model of translocation. We estimated the energy associated with crossing the inner mitochondrial membrane. We found that the transmembrane potential provides sufficient energy for the peptide to cross the hydrophobic core, which is the most unfavorable step in translocation.
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Affiliation(s)
- Lauren E Marbella
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, USA.
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22
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Ghimire H, Abu-Baker S, Sahu ID, Zhou A, Mayo DJ, Lee RT, Lorigan GA. Probing the helical tilt and dynamic properties of membrane-bound phospholamban in magnetically aligned bicelles using electron paramagnetic resonance spectroscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1818:645-50. [PMID: 22172806 DOI: 10.1016/j.bbamem.2011.11.030] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2011] [Revised: 11/18/2011] [Accepted: 11/24/2011] [Indexed: 10/14/2022]
Abstract
Wild-type phospholamban (WT-PLB), a Ca(2+)-ATPase (SERCA) regulator in the sarcoplasmic reticulum membrane, was studied using TOAC nitroxide spin labeling, magnetically aligned bicelles, and electron paramagnetic resonance (EPR) spectroscopy to ascertain structural and dynamic information. Different structural domains of PLB (transmembrane segment: positions 42 and 45, loop region: position 20, and cytoplasmic domain: position 10) were probed with rigid TOAC spin labels to extract the transmembrane helical tilt and structural dynamic information, which is crucial for understanding the regulatory function of PLB in modulating Ca(2+)-ATPase activity. Aligned experiments indicate that the transmembrane domain of wild-type PLB has a helical tilt of 13°±4° in DMPC/DHPC bicelles. TOAC spin labels placed on the WT-PLB transmembrane domain showed highly restricted motion with more than 100ns rotational correlation time (τ(c)); whereas the loop, and the cytoplasmic regions each consists of two distinct motional dynamics: one fast component in the sub-nanosecond scale and the other component is slower dynamics in the nanosecond range.
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23
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Structural topology of phospholamban pentamer in lipid bilayers by a hybrid solution and solid-state NMR method. Proc Natl Acad Sci U S A 2011; 108:9101-6. [PMID: 21576492 DOI: 10.1073/pnas.1016535108] [Citation(s) in RCA: 132] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Phospholamban (PLN) is a type II membrane protein that inhibits the sarcoplasmic reticulum Ca(2+)-ATPase (SERCA), thereby regulating calcium homeostasis in cardiac muscle. In membranes, PLN forms pentamers that have been proposed to function either as a storage for active monomers or as ion channels. Here, we report the T-state structure of pentameric PLN solved by a hybrid solution and solid-state NMR method. In lipid bilayers, PLN adopts a pinwheel topology with a narrow hydrophobic pore, which excludes ion transport. In the T state, the cytoplasmic amphipathic helices (domains Ia) are absorbed into the lipid bilayer with the transmembrane domains arranged in a left-handed coiled-coil configuration, crossing the bilayer with a tilt angle of approximately 11° with respect to the membrane normal. The tilt angle difference between the monomer and pentamer is approximately 13°, showing that intramembrane helix-helix association forces dominate over the hydrophobic mismatch, driving the overall topology of the transmembrane assembly. Our data reveal that both topology and function of PLN are shaped by the interactions with lipids, which fine-tune the regulation of SERCA.
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24
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Gustavsson M, Traaseth NJ, Karim CB, Lockamy EL, Thomas DD, Veglia G. Lipid-mediated folding/unfolding of phospholamban as a regulatory mechanism for the sarcoplasmic reticulum Ca2+-ATPase. J Mol Biol 2011; 408:755-65. [PMID: 21419777 DOI: 10.1016/j.jmb.2011.03.015] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2010] [Revised: 01/10/2011] [Accepted: 03/07/2011] [Indexed: 10/18/2022]
Abstract
The integral membrane protein complex between phospholamban (PLN) and sarcoplasmic reticulum Ca(2+)-ATPase (SERCA) regulates cardiac contractility. In the unphosphorylated form, PLN binds SERCA and inhibits Ca(2+) flux. Upon phosphorylation of PLN at Ser16, the inhibitory effect is reversed. Although structural details on both proteins are emerging from X-ray crystallography, cryo-electron microscopy, and NMR studies, the molecular mechanisms of their interactions and regulatory process are still lacking. It has been speculated that SERCA regulation depends on PLN structural transitions (order to disorder, i.e., folding/unfolding). Here, we investigated PLN conformational changes upon chemical unfolding by a combination of electron paramagnetic resonance and NMR spectroscopies, revealing that the conformational transitions involve mostly the cytoplasmic regions, with two concomitant phenomena: (1) membrane binding and folding of the amphipathic domain Ia and (2) folding/unfolding of the juxtamembrane domain Ib of PLN. Analysis of phosphorylated and unphosphorylated PLN with two phosphomimetic mutants of PLN (S16E and S16D) shows that the population of an unfolded state in domains Ia and Ib (T' state) is linearly correlated to the extent of SERCA inhibition measured by activity assays. Inhibition of SERCA is carried out by the folded ground state (T state) of the protein (PLN), while the relief of inhibition involves promotion of PLN to excited conformational states (Ser16 phosphorylated PLN). We propose that PLN population shifts (folding/unfolding) are a key regulatory mechanism for SERCA.
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Affiliation(s)
- Martin Gustavsson
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
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25
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Manna M, Mukhopadhyay C. Cholesterol driven alteration of the conformation and dynamics of phospholamban in model membranes. Phys Chem Chem Phys 2011; 13:20188-98. [DOI: 10.1039/c1cp21793c] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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26
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Chu S, Abu-Baker S, Lu J, Lorigan GA. (15)N Solid-state NMR spectroscopic studies on phospholamban at its phosphorylated form at ser-16 in aligned phospholipid bilayers. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:312-7. [PMID: 20044975 DOI: 10.1016/j.bbamem.2009.12.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2009] [Revised: 12/18/2009] [Accepted: 12/22/2009] [Indexed: 11/17/2022]
Abstract
Wild-type phospholamban (WT-PLB) is a pentameric transmembrane protein that regulates the cardiac cycle (contraction and relaxation). From a physiological prospective, unphosphorylated WT-PLB inhibits sarcoplasmic reticulum ATPase activity; whereas, its phosphorylated form relieves the inhibition in a mechanism that is not completely understood. In this study, site-specifically (15)N-Ala-11- and (15)N-Leu-7-labeled WT-PLB and the corresponding phosphorylated forms (P-PLB) were incorporated into 1,2-dioleoyl-sn-glycero-3-phosphocholine/2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPC/DOPE) mechanically oriented lipid bilayers. The aligned (15)N-labeled Ala-11 and Leu-7 WT-PLB samples show (15)N resonance peaks at approximately 71ppm and 75ppm, respectively, while the corresponding phosphorylated forms P-PLB show (15)N peaks at 92ppm and 99ppm, respectively. These (15)N chemical shift changes upon phosphorylation are significant and in agreement with previous reports, which indicate that phosphorylation of WT-PLB at Ser-16 alters the structural properties of the cytoplasmic domain with respect to the lipid bilayers.
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Affiliation(s)
- Shidong Chu
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio 45056, USA
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27
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Solid-state (2)H and (15)N NMR studies of side-chain and backbone dynamics of phospholamban in lipid bilayers: investigation of the N27A mutation. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1798:210-5. [PMID: 19840770 DOI: 10.1016/j.bbamem.2009.09.025] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2009] [Revised: 09/18/2009] [Accepted: 09/30/2009] [Indexed: 11/23/2022]
Abstract
Phospholamban (PLB) is an integral membrane protein regulating Ca(2+) transport through inhibitory interaction with sarco(endo)plasmic reticulum calcium ATPase (SERCA). The Asn27 to Ala (N27A) mutation of PLB has been shown to function as a superinhibitor of the affinity of SERCA for Ca(2+) and of cardiac contractility in vivo. The effects of this N27A mutation on the side-chain and backbone dynamics of PLB were investigated with (2)H and (15)N solid-state NMR spectroscopy in phospholipid multilamellar vesicles (MLVs). (2)H and (15)N NMR spectra indicate that the N27A mutation does not significantly change the side-chain or backbone dynamics of the transmembrane and cytoplasmic domains when compared to wild-type PLB. However, dynamic changes are observed for the hinge region, in which greater mobility is observed for the CD(3)-labeled Ala24 N27A-PLB. The increased dynamics in the hinge region of PLB upon N27A mutation may allow the cytoplasmic helix to more easily interact with the Ca(2+)-ATPase; thus, showing increased inhibition of Ca(2+)-ATPase.
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28
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Teriete P, Thai K, Choi J, Marassi FM. Effects of PKA phosphorylation on the conformation of the Na,K-ATPase regulatory protein FXYD1. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1788:2462-70. [PMID: 19761758 DOI: 10.1016/j.bbamem.2009.09.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2009] [Revised: 08/21/2009] [Accepted: 09/06/2009] [Indexed: 12/17/2022]
Abstract
FXYD1 (phospholemman) is a member of an evolutionarily conserved family of membrane proteins that regulate the function of the Na,K-ATPase enzyme complex in specific tissues and specific physiological states. In heart and skeletal muscle sarcolemma, FXYD1 is also the principal substrate of hormone-regulated phosphorylation by c-AMP dependent protein kinase A and by protein kinase C, which phosphorylate the protein at conserved Ser residues in its cytoplasmic domain, altering its Na,K-ATPase regulatory activity. FXYD1 adopts an L-shaped alpha-helical structure with the transmembrane helix loosely connected to a cytoplasmic amphipathic helix that rests on the membrane surface. In this paper we describe NMR experiments showing that neither PKA phosphorylation at Ser68 nor the physiologically relevant phosphorylation mimicking mutation Ser68Asp induces major changes in the protein conformation. The results, viewed in light of a model of FXYD1 associated with the Na,K-ATPase alpha and beta subunits, indicate that the effects of phosphorylation on the Na,K-ATPase regulatory activity of FXYD1 could be due primarily to changes in electrostatic potential near the membrane surface and near the Na(+)/K(+) ion binding site of the Na,K-ATPase alpha subunit.
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Affiliation(s)
- Peter Teriete
- Burnham Institute for Medical Research, 10901 North Torrey Pines Road, La Jolla, CA 92037, USA
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29
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Newstadt JP, Mayo DJ, Inbaraj JJ, Subbaraman N, Lorigan GA. Determining the helical tilt of membrane peptides using electron paramagnetic resonance spectroscopy. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2009; 198:1-7. [PMID: 19254856 PMCID: PMC2666113 DOI: 10.1016/j.jmr.2008.12.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2008] [Revised: 12/05/2008] [Accepted: 12/05/2008] [Indexed: 05/26/2023]
Abstract
Theoretical calculations of hyperfine splitting values derived from the EPR spectra of TOAC spin-labeled rigid aligned alpha-helical membrane peptides reveal a unique periodic variation. In the absence of helical motion, a plot of the corresponding hyperfine splitting values as a function of residue number results in a sinusoidal curve that depends on the helical tilt angle that the peptide makes with respect to the magnetic field. Motion about the long helical axis reduces the amplitude of the curve and averages out the corresponding hyperfine splitting values. The corresponding spectra can be used to determine the director axis tilt angle from the TOAC spin label, which can be used to calculate the helical tilt angle due to the rigidity of the TOAC spin label. Additionally, this paper describes a method to experimentally determine this helical tilt angle from the hyperfine splitting values of three consecutive residues.
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Affiliation(s)
- Justin P Newstadt
- Department of Chemistry and Biochemistry, Miami University of Ohio, Room 137, Hughes Laboratories, Oxford, OH 45056-1465, USA
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30
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Hou Z, Kelly EM, Robia SL. Phosphomimetic mutations increase phospholamban oligomerization and alter the structure of its regulatory complex. J Biol Chem 2008; 283:28996-9003. [PMID: 18708665 DOI: 10.1074/jbc.m804782200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
To investigate the effect of phosphorylation on the interactions of phospholamban (PLB) with itself and its regulatory target, SERCA, we measured FRET from CFP-SERCA or CFP-PLB to YFP-PLB in live AAV-293 cells. Phosphorylation of PLB was mimicked by mutations S16E (PKA site) or S16E/T17E (PKA+CaMKII sites). FRET increased with protein concentration up to a maximum (FRET(max)) that was taken to represent the intrinsic FRET of the bound complex. The concentration dependence of FRET yielded dissociation constants (K(D)) for the PLB-PLB and PLB-SERCA interactions. PLB-PLB FRET data suggest pseudo-phosphorylation of PLB increased oligomerization of PLB but did not alter PLB pentamer quaternary structure. PLB-SERCA FRET experiments showed an apparent decrease in binding of PLB to SERCA and an increase in the apparent PLB-SERCA binding cooperativity. It is likely that these changes are secondary effects of increased oligomerization of PLB; a change in the inherent affinity of monomeric PLB for SERCA was not detected. In addition, PLB-SERCA complex FRET(max) was reduced by phosphomimetic mutations, suggesting the conformation of the regulatory complex is significantly altered by PLB phosphorylation.
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Affiliation(s)
- Zhanjia Hou
- Department of Physiology, Loyola University Chicago, Maywood, Illinois 60153, USA
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31
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Qiang W, Bodner ML, Weliky DP. Solid-state NMR spectroscopy of human immunodeficiency virus fusion peptides associated with host-cell-like membranes: 2D correlation spectra and distance measurements support a fully extended conformation and models for specific antiparallel strand registries. J Am Chem Soc 2008; 130:5459-71. [PMID: 18370385 DOI: 10.1021/ja077302m] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The human immunodeficiency virus (HIV) is "enveloped" by a membrane, and infection of a host cell begins with fusion between viral and target cell membranes. Fusion is catalyzed by the HIV gp41 protein which contains a functionally critical approximately 20-residue apolar "fusion peptide" (HFP) that associates with target cell membranes. In this study, chemically synthesized HFPs were associated with host-cell-like membranes and had "scatter-uniform" labeling (SUL), that is, only one residue of each amino acid type was U-(13)C, (15)N labeled. For the first sixteen HFP residues, an unambiguous (13)C chemical shift assignment was derived from 2D (13)C/(13)C correlation spectra with short mixing times, and the shifts were consistent with continuous beta-strand conformation. (13)C-(13)C contacts between residues on adjacent strands were derived from correlation spectra with long mixing times and suggested close proximity of the following residues: Ala-6/Gly-10, Ala-6/Phe-11, and Ile-4/Gly-13. Specific antiparallel beta-strand registries were further tested using a set of HFPs that were (13)CO-labeled at Ala-14 and (15)N-labeled at either Val-2, Gly-3, Ile-4, or Gly-5. The solid-state NMR data were fit with 50-60% population of antiparallel HFP with either Ala-14/Gly-3 or Ala-14/Ile-4 registries and 40-50% population of structures not specified by the NMR experiments. The first two registries correlated with intermolecular hydrogen bonding of 15-16 apolar N-terminal residues and this hydrogen-bonding pattern would be consistent with a predominant location of these residues in the hydrophobic membrane interior. To our knowledge, these results provide the first residue-specific structural models for membrane-associated HFP in its beta-strand conformation.
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Affiliation(s)
- Wei Qiang
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, USA
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32
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Kelly EM, Hou Z, Bossuyt J, Bers DM, Robia SL. Phospholamban oligomerization, quaternary structure, and sarco(endo)plasmic reticulum calcium ATPase binding measured by fluorescence resonance energy transfer in living cells. J Biol Chem 2008; 283:12202-11. [PMID: 18287099 DOI: 10.1074/jbc.m707590200] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phospholamban (PLB) oligomerization, quaternary structure, and sarco(endo)plasmic reticulum calcium ATPase (SERCA) binding were quantified by fluorescence resonance energy transfer (FRET) in an intact cellular environment. FRET between cyan fluorescent protein-PLB and yellow fluorescent protein-PLB in AAV-293 cells showed hyperbolic dependence on protein concentration, with a maximum efficiency of 45.1 +/- 1.3%. The observed FRET corresponds to a probe separation distance of 58.7 +/- 0.5A(,) according to a computational model of intrapentameric FRET. This is consistent with models of the PLB pentamer in which cytoplasmic domains fan out from the central bundle of transmembrane helices. An I40A mutation of PLB did not alter pentamer conformation but increased the concentration of half-maximal FRET (K(D)) by >4-fold. This is consistent with the previous observation that this putatively monomeric mutant still oligomerizes in intact membranes but forms more dynamic pentamers than wild type PLB. PLB association with SERCA, measured by FRET between cyan fluorescent protein-SERCA and yellow fluorescent protein-PLB, was increased by the I40A mutation without any detectable change in probe separation distance. The data indicate that the regulatory complex conformation is not altered by the I40A mutation. A naturally occurring human mutation (L39Stop) greatly reduced PLB oligomerization and SERCA binding and caused mislocalization of PLB to the cytoplasm and nucleus. Overall, the data suggest that the PLB pentamer adopts a "pinwheel" shape in cell membranes, as opposed to a more compact "bellflower" conformation. I40A mutation decreases oligomerization and increases PLB binding to SERCA. Truncation of the transmembrane domain by L39Stop mutation prevents anchoring of the protein in the membrane, greatly reducing PLB binding to itself or its regulatory target, SERCA.
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Affiliation(s)
- Eileen M Kelly
- Department of Physiology, Loyola University Chicago, Maywood, Illinois 60153,USA
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33
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Oxenoid K, Rice AJ, Chou JJ. Comparing the structure and dynamics of phospholamban pentamer in its unphosphorylated and pseudo-phosphorylated states. Protein Sci 2007; 16:1977-83. [PMID: 17766390 PMCID: PMC2206959 DOI: 10.1110/ps.072975107] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Human phospholamban (PLN), a 30 kDa homopentamer in the sarcoplasmic reticulum (SR) membrane, controls the magnitude of heart muscle contraction and relaxation by regulating the calcium pumping activity of the SR Ca(2+)-ATPase (SERCA). When PLN is not phosphorylated, it binds and inhibits SERCA. Phosphorylation of PLN at S16 or T17 releases such inhibitory effect. It remains a matter of debate whether phosphorylation perturbs the structure of PLN, which in turn affects its interaction with SERCA. Here we examine by NMR spectroscopy the structure and dynamics of PLN pentamer with a physiologically relevant, phosphorylation-mimicking mutation, S16E. Based on extensive NMR data, including NOEs, dipolar couplings, and solvent exchange of backbone amides, we conclude that the phosphorylation-mimicking mutation does not perturb the pentamer structure. However, (15)N R(1) and R(2) relaxation rates and (15)N((1)H) NOEs suggest subtle differences in the dynamics of the extramembrane portion of the protein.
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Affiliation(s)
- Kirill Oxenoid
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA
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34
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Liu W, Fei JZ, Kawakami T, Smith SO. Structural constraints on the transmembrane and juxtamembrane regions of the phospholamban pentamer in membrane bilayers: Gln29 and Leu52. BIOCHIMICA ET BIOPHYSICA ACTA 2007; 1768:2971-8. [PMID: 17996192 PMCID: PMC2715955 DOI: 10.1016/j.bbamem.2007.10.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2007] [Revised: 10/09/2007] [Accepted: 10/15/2007] [Indexed: 10/22/2022]
Abstract
The Ca2+-ATPase of cardiac muscle cells transports Ca2+ ions against a concentration gradient into the sarcoplasmic reticulum and is regulated by phospholamban, a 52-residue integral membrane protein. It is known that phospholamban inhibits the Ca2+ pump during muscle contraction and that inhibition is removed by phosphorylation of the protein during muscle relaxation. Phospholamban forms a pentameric complex with a central pore. The solid-state magic angle spinning (MAS) NMR measurements presented here address the structure of the phospholamban pentamer in the region of Gln22-Gln29. Rotational echo double resonance (REDOR) NMR measurements show that the side chain amide groups of Gln29 are in close proximity, consistent with a hydrogen-bonded network within the central pore. 13C MAS NMR measurements are also presented on phospholamban that is 1-13C-labeled at Leu52, the last residue of the protein. pH titration of the C-terminal carboxyl group suggests that it forms a ring of negative charge on the lumenal side of the sarcoplasmic reticulum membrane. The structural constraints on the phospholamban pentamer described in this study are discussed in the context of a multifaceted mechanism for Ca2+ regulation that may involve phospholamban as both an inhibitor of the Ca2+ ATPase and as an ion channel.
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Affiliation(s)
- Wei Liu
- Department of Biochemistry and Cell Biology, Center for Structural Biology, Stony Brook University, Stony Brook, NY 11794-5115
| | - Jeffrey Z. Fei
- Department of Biochemistry and Cell Biology, Center for Structural Biology, Stony Brook University, Stony Brook, NY 11794-5115
| | - Toru Kawakami
- Institute for Protein Research, Osaka University, Osaka, Japan
| | - Steven O. Smith
- Department of Biochemistry and Cell Biology, Center for Structural Biology, Stony Brook University, Stony Brook, NY 11794-5115
- Institute for Protein Research, Osaka University, Osaka, Japan
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35
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Abu-Baker S, Lu JX, Chu S, Brinn CC, Makaroff CA, Lorigan GA. Side chain and backbone dynamics of phospholamban in phospholipid bilayers utilizing 2H and 15N solid-state NMR spectroscopy. Biochemistry 2007; 46:11695-706. [PMID: 17910421 PMCID: PMC2756648 DOI: 10.1021/bi700749q] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
2H and 15N solid-state NMR spectroscopic techniques were used to investigate both the side chain and backbone dynamics of wild-type phospholamban (WT-PLB) and its phosphorylated form (P-PLB) incorporated into 1-palmitoyl-2-oleoyl-sn-glycerophosphocholine (POPC) phospholipid bilayers. 2H NMR spectra of site-specific CD3-labeled WT-PLB (at Leu51, Ala24, and Ala15) in POPC bilayers were similar under frozen conditions (-25 degrees C). However, significant differences in the line shapes of the 2H NMR spectra were observed in the liquid crystalline phase at and above 0 degrees C. The 2H NMR spectra indicate that Leu51, located toward the lower end of the transmembrane (TM) helix, shows restricted side chain motion, implying that it is embedded inside the POPC lipid bilayer. Additionally, the line shape of the 2H NMR spectrum of CD3-Ala24 reveals more side chain dynamics, indicating that this residue (located in the upper end of the TM helix) has additional backbone and internal side chain motions. 2H NMR spectra of both WT-PLB and P-PLB with CD3-Ala15 exhibit strong isotropic spectral line shapes. The dynamic isotropic nature of the 2H peak can be attributed to side chain and backbone motions to residues located in an aqueous environment outside the membrane. Also, the spectra of 15N-labeled amide WT-PLB at Leu51 and Leu42 residues showed only a single powder pattern component indicating that these two 15N-labeled residues located in the TM helix are motionally restricted at 25 degrees C. Conversely, 15N-labeled amide WT-PLB at Ala11 located in the cytoplasmic domain showed both powder and isotropic components at 25 degrees C. Upon phosphorylation, the mobile component contribution increases at Ala11. The 2H and 15N NMR data indicate significant backbone motion for the cytoplasmic domain of WT-PLB when compared to the transmembrane section.
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Affiliation(s)
- Shadi Abu-Baker
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio 45056, USA
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36
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Abu-Baker S, Lu JX, Chu S, Shetty KK, Gor'kov PL, Lorigan GA. The structural topology of wild-type phospholamban in oriented lipid bilayers using 15N solid-state NMR spectroscopy. Protein Sci 2007; 16:2345-9. [PMID: 17905829 PMCID: PMC2211705 DOI: 10.1110/ps.072977707] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
For the first time, 15N solid-state NMR experiments were conducted on wild-type phospholamban (WT-PLB) embedded inside mechanically oriented phospholipid bilayers to investigate the topology of its cytoplasmic and transmembrane domains. 15N solid-state NMR spectra of site-specific 15N-labeled WT-PLB indicate that the transmembrane domain has a tilt angle of 13 degrees+/-6 degrees with respect to the POPC (1-palmitoyl-2-oleoyl-sn-glycero-phosphocholine) bilayer normal and that the cytoplasmic domain of WT-PLB lies on the surface of the phospholipid bilayers. Comparable results were obtained from site-specific 15N-labeled WT-PLB embedded inside DOPC/DOPE (1,2-dioleoyl-sn-glycero-3-phosphocholine/1,2-dioleoyl-sn-glycero-3-phosphoethanolamine) mechanically oriented phospholipids' bilayers. The new NMR data support a pinwheel geometry of WT-PLB, but disagree with a bellflower structure in micelles, and indicate that the orientation of the cytoplasmic domain of the WT-PLB is similar to that reported for the monomeric AFA-PLB mutant.
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Affiliation(s)
- Shadi Abu-Baker
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA
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37
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Traaseth NJ, Verardi R, Torgersen KD, Karim CB, Thomas DD, Veglia G. Spectroscopic validation of the pentameric structure of phospholamban. Proc Natl Acad Sci U S A 2007; 104:14676-81. [PMID: 17804809 PMCID: PMC1976191 DOI: 10.1073/pnas.0701016104] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2007] [Indexed: 11/18/2022] Open
Abstract
Phospholamban (PLN) regulates calcium translocation within cardiac myocytes by shifting sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) affinity for calcium. Although the monomeric form of PLN (6 kDa) is the principal inhibitory species, recent evidence suggests that the PLN pentamer (30 kDa) also is able to bind SERCA. To date, several membrane architectures of the pentamer have been proposed, with different topological orientations for the cytoplasmic domain: (i) extended from the bilayer normal by 50-60 degrees; (ii) continuous alpha-helix tilted 28 degrees relative to the bilayer normal; (iii) pinwheel geometry, with the cytoplasmic helix perpendicular to the bilayer normal and in contact with the surface of the bilayer; and (iv) bellflower structure, in which the cytoplasmic domain helix makes approximately 20 degrees angle with respect to the membrane bilayer normal. Using a variety of cell membrane mimicking systems (i.e., lipid vesicles, oriented lipid bilayers, and detergent micelles) and a combination of multidimensional solution/solid-state NMR and EPR spectroscopies, we tested the different structural models. We conclude that the pinwheel topology is the predominant conformation of pentameric PLN, with the cytoplasmic domain interacting with the membrane surface. We propose that the interaction with the bilayer precedes SERCA binding and may mediate the interactions with other proteins such as protein kinase A and protein phosphatase 1.
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Affiliation(s)
| | - Raffaello Verardi
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455
| | - Kurt D. Torgersen
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455
| | - Christine B. Karim
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455
| | - David D. Thomas
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455
| | - Gianluigi Veglia
- *Department of Chemistry, and
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455
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38
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Abu-Baker S, Qi X, Lorigan GA. Investigating the interaction of saposin C with POPS and POPC phospholipids: a solid-state NMR spectroscopic study. Biophys J 2007; 93:3480-90. [PMID: 17704143 PMCID: PMC2072076 DOI: 10.1529/biophysj.107.107789] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The interaction of Saposin C (Sap C) with negatively charged phospholipids such as phosphatidylserine (PS) is essential for its biological function. In this study, Sap C (initially protonated in a weak acid) was inserted into multilamellar vesicles (MLVs) consisting of either 1-palmitoyl-2-oleoyl-sn-glycero-3-[phospho-L-serine] (negatively charged, POPS) or 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (neutrally charged, POPC). The MLVs were then investigated using solid-state NMR spectroscopy under neutral pH (7.0) conditions. The (2)H and (31)P solid-state NMR spectroscopic data of Sap C-POPS and Sap C-POPC MLVs (prepared under the same conditions) were compared using the (2)H order parameter profiles of the POPC-d(31) or POPS-d(31) acyl chains as well as the (31)P chemical shift anisotropy width and (31)P T(1) relaxation times of the phospholipids headgroups. All those solid-state NMR spectroscopic approaches indicate that protonated Sap C disturbs the POPS bilayers and not the POPC lipid bilayers. These observations suggest for the first time that protonated Sap C inserts into PS bilayers and forms a stable complex with the lipids even after resuspension under neutral buffer conditions. Additionally, (31)P solid-state NMR spectroscopic studies of mechanically oriented phospholipids on glass plates were conducted and perturbation effect of Sap C on both POPS and POPC bilayers was compared. Unlike POPC bilayers, the data indicates that protonated Sap C (initially protonated in a weak acid) was unable to produce well-oriented POPS bilayers on glass plates at neutral pH. Conversely, unprotonated Sap C (initially dissolved in a neutral buffer) did not interact significantly with POPS phospholipids allowing them to produce well-oriented bilayers at neutral pH.
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Affiliation(s)
- Shadi Abu-Baker
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio, USA
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