1
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Duan HD, Li H. Consensus, controversies, and conundrums of P4-ATPases: The emerging face of eukaryotic lipid flippases. J Biol Chem 2024; 300:107387. [PMID: 38763336 PMCID: PMC11225554 DOI: 10.1016/j.jbc.2024.107387] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2024] [Revised: 05/04/2024] [Accepted: 05/07/2024] [Indexed: 05/21/2024] Open
Abstract
The cryo-EM resolution revolution has heralded a new era in our understanding of eukaryotic lipid flippases with a rapidly growing number of high-resolution structures. Flippases belong to the P4 family of ATPases (type IV P-type ATPases) that largely follow the reaction cycle proposed for the more extensively studied cation-transporting P-type ATPases. However, unlike the canonical P-type ATPases, no flippase cargos are transported in the phosphorylation half-reaction. Instead of being released into the intracellular or extracellular milieu, lipid cargos are transported to their destination at the inner leaflet of the membrane. Recent flippase structures have revealed multiple conformational states during the lipid transport cycle. Nonetheless, critical conformational states capturing the lipid cargo "in transit" are still missing. In this review, we highlight the amazing structural advances of these lipid transporters, discuss various perspectives on catalytic and regulatory mechanisms in the literature, and shed light on future directions in further deciphering the detailed molecular mechanisms of lipid flipping.
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Affiliation(s)
- H Diessel Duan
- Department of Structural Biology, Van Andel Institute, Grand Rapids, Michigan, USA.
| | - Huilin Li
- Department of Structural Biology, Van Andel Institute, Grand Rapids, Michigan, USA.
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2
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Palmgren M, Morth JP, Nissen P. TMEM94 cannot be called a P-type ATPase. Cell Calcium 2024; 123:102911. [PMID: 38879951 DOI: 10.1016/j.ceca.2024.102911] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2024] [Revised: 05/23/2024] [Accepted: 05/24/2024] [Indexed: 06/18/2024]
Affiliation(s)
- Michael Palmgren
- Department of Plant and Environmental Sciences, University of Copenhagen, Frederiksberg, Denmark.
| | - Jens Preben Morth
- Department of Biotechnology & Biomedicine, Technical University of Denmark, Kongens Lyngby, Denmark.
| | - Poul Nissen
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark.
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3
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Vishnu N, Venkatesan M, Madaris TR, Venkateswaran MK, Stanley K, Ramachandran K, Chidambaram A, Madesh AK, Yang W, Nair J, Narkunan M, Muthukumar T, Karanam V, Joseph LC, Le A, Osidele A, Aslam MI, Morrow JP, Malicdan MC, Stathopulos PB, Madesh M. ERMA (TMEM94) is a P-type ATPase transporter for Mg 2+ uptake in the endoplasmic reticulum. Mol Cell 2024; 84:1321-1337.e11. [PMID: 38513662 PMCID: PMC10997467 DOI: 10.1016/j.molcel.2024.02.033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2023] [Revised: 10/16/2023] [Accepted: 02/27/2024] [Indexed: 03/23/2024]
Abstract
Intracellular Mg2+ (iMg2+) is bound with phosphometabolites, nucleic acids, and proteins in eukaryotes. Little is known about the intracellular compartmentalization and molecular details of Mg2+ transport into/from cellular organelles such as the endoplasmic reticulum (ER). We found that the ER is a major iMg2+ compartment refilled by a largely uncharacterized ER-localized protein, TMEM94. Conventional and AlphaFold2 predictions suggest that ERMA (TMEM94) is a multi-pass transmembrane protein with large cytosolic headpiece actuator, nucleotide, and phosphorylation domains, analogous to P-type ATPases. However, ERMA uniquely combines a P-type ATPase domain and a GMN motif for ERMg2+ uptake. Experiments reveal that a tyrosine residue is crucial for Mg2+ binding and activity in a mechanism conserved in both prokaryotic (mgtB and mgtA) and eukaryotic Mg2+ ATPases. Cardiac dysfunction by haploinsufficiency, abnormal Ca2+ cycling in mouse Erma+/- cardiomyocytes, and ERMA mRNA silencing in human iPSC-cardiomyocytes collectively define ERMA as an essential component of ERMg2+ uptake in eukaryotes.
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Affiliation(s)
- Neelanjan Vishnu
- Department of Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA; Center for Mitochondrial Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Manigandan Venkatesan
- Department of Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA; Center for Mitochondrial Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Travis R Madaris
- Department of Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA; Center for Mitochondrial Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Mridula K Venkateswaran
- Department of Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA; Center for Mitochondrial Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Kristen Stanley
- Department of Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA; Center for Mitochondrial Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Karthik Ramachandran
- Department of Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA; Center for Mitochondrial Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Adhishree Chidambaram
- Department of Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA; Center for Mitochondrial Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Abitha K Madesh
- Department of Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA; Center for Mitochondrial Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Wenli Yang
- Institute for Regenerative Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Jyotsna Nair
- Department of Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA; Center for Mitochondrial Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Melanie Narkunan
- Department of Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA; Center for Mitochondrial Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Tharani Muthukumar
- Department of Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA; Center for Mitochondrial Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Varsha Karanam
- Department of Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA; Center for Mitochondrial Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Leroy C Joseph
- Department of Medicine, College of Physicians and Surgeons of Columbia University, 650 W 168 Street, New York, NY 10032, USA
| | - Amy Le
- Department of Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA; Center for Mitochondrial Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Ayodeji Osidele
- Department of Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA; Center for Mitochondrial Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - M Imran Aslam
- Department of Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA; Center for Mitochondrial Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - John P Morrow
- Department of Medicine, College of Physicians and Surgeons of Columbia University, 650 W 168 Street, New York, NY 10032, USA
| | - May C Malicdan
- Section of Human Biochemical Genetics, Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA; NIH Undiagnosed Diseases Program, Office of the Clinical Director, National Human Genome Research Institute, and the Common Fund, National Institutes of Health, Bethesda, MD 20892, USA
| | - Peter B Stathopulos
- Department of Physiology and Pharmacology, Western University, London, ON N6A 5C1, Canada
| | - Muniswamy Madesh
- Department of Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA; Center for Mitochondrial Medicine, University of Texas Health San Antonio, San Antonio, TX 78229, USA.
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4
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Wu M, Wu C, Song T, Pan K, Wang Y, Liu Z. Structure and transport mechanism of the human calcium pump SPCA1. Cell Res 2023; 33:533-545. [PMID: 37258749 PMCID: PMC10313705 DOI: 10.1038/s41422-023-00827-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Accepted: 05/08/2023] [Indexed: 06/02/2023] Open
Abstract
Secretory-pathway Ca2+-ATPases (SPCAs) play critical roles in maintaining Ca2+ homeostasis, but the exact mechanism of SPCAs-mediated Ca2+ transport remains unclear. Here, we determined six cryo-electron microscopy (cryo-EM) structures of human SPCA1 (hSPCA1) in a series of intermediate states, revealing a near-complete conformational cycle. With the aid of molecular dynamics simulations, these structures offer a clear structural basis for Ca2+ entry and release in hSPCA1. We found that hSPCA1 undergoes unique conformational changes during ATP binding and phosphorylation compared to other well-studied P-type II ATPases. In addition, we observed a conformational distortion of the Ca2+-binding site induced by the separation of transmembrane helices 4L and 6, unveiling a distinct Ca2+ release mechanism. Particularly, we determined a structure of the long-sought CaE2P state of P-type IIA ATPases, providing valuable insights into the Ca2+ transport cycle. Together, these findings enhance our understanding of Ca2+ transport by hSPCA1 and broaden our knowledge of P-type ATPases.
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Affiliation(s)
- Mengqi Wu
- Department of Immunology and Microbiology, School of Life Sciences, Southern University of Science and Technology, Shenzhen, Guangdong, China
| | - Cang Wu
- Department of Immunology and Microbiology, School of Life Sciences, Southern University of Science and Technology, Shenzhen, Guangdong, China
| | - Tiefeng Song
- College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
| | - Kewu Pan
- School of Biomedical Sciences, The Chinese University of Hong Kong, Hong Kong, China
| | - Yong Wang
- College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China.
- The Provincial International Science and Technology Cooperation Base on Engineering Biology, International Campus of Zhejiang University, Haining, Zhejiang, China.
| | - Zhongmin Liu
- Department of Immunology and Microbiology, School of Life Sciences, Southern University of Science and Technology, Shenzhen, Guangdong, China.
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5
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Stalke A, Behrendt A, Hennig F, Gohlke H, Buhl N, Reinkens T, Baumann U, Schlegelberger B, Illig T, Pfister ED, Skawran B. Functional characterization of novel or yet uncharacterized ATP7B missense variants detected in patients with clinical Wilson's disease. Clin Genet 2023. [PMID: 37157876 DOI: 10.1111/cge.14352] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2023] [Revised: 04/14/2023] [Accepted: 04/20/2023] [Indexed: 05/10/2023]
Abstract
Wilson's disease (WD, MIM#277900) is an autosomal recessive disorder resulting in copper excess caused by biallelic variants in the ATP7B gene (MIM#606882) encoding a copper transporting P-type ATPase. ATP7B variants of unknown significance (VUS) are detected frequently, sometimes impeding a clear diagnosis. Functional analyses can help to classify these variants as benign or pathogenic. Additionally, variants already classified as (likely) pathogenic benefit from functional analyses to understand their pathomechanism, thus contribute to the development of personalized treatment approaches in the future. We described clinical features of six WD patients and functionally characterized five ATP7B missense variants (two VUS, three yet uncharacterized likely pathogenic variants), detected in these patients. We determined the protein level, copper export capacity, and cellular localization in an in vitro model and potential structural consequences using an ATP7B protein model based on AlphaFold. Our analyses give insight into the pathomechanism and allowed reclassification for the two VUS to likely pathogenic and for two of the three likely pathogenic variants to pathogenic.
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Affiliation(s)
- Amelie Stalke
- Department of Human Genetics, Hannover Medical School, Hannover, Germany
- Department of Pediatric Gastroenterology and Hepatology, Division of Kidney, Liver, and Metabolic Diseases, Hannover Medical School, Hannover, Germany
| | - Annika Behrendt
- Institute for Pharmaceutical and Medicinal Chemistry, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Finja Hennig
- Department of Human Genetics, Hannover Medical School, Hannover, Germany
| | - Holger Gohlke
- Institute for Pharmaceutical and Medicinal Chemistry, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
- Institute of Bio- and Geosciences (IBG-4: Bioinformatics), Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Nicole Buhl
- Department of Human Genetics, Hannover Medical School, Hannover, Germany
- Department of Pediatric Gastroenterology and Hepatology, Division of Kidney, Liver, and Metabolic Diseases, Hannover Medical School, Hannover, Germany
| | - Thea Reinkens
- Department of Human Genetics, Hannover Medical School, Hannover, Germany
| | - Ulrich Baumann
- Department of Pediatric Gastroenterology and Hepatology, Division of Kidney, Liver, and Metabolic Diseases, Hannover Medical School, Hannover, Germany
| | | | - Thomas Illig
- Hannover Unified Bank, Hannover Medical School, Hannover, Germany
| | - Eva-Doreen Pfister
- Department of Pediatric Gastroenterology and Hepatology, Division of Kidney, Liver, and Metabolic Diseases, Hannover Medical School, Hannover, Germany
| | - Britta Skawran
- Department of Human Genetics, Hannover Medical School, Hannover, Germany
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6
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Guo Y, Zhang Y, Yan R, Huang B, Ye F, Wu L, Chi X, Shi Y, Zhou Q. Cryo-EM structures of recombinant human sodium-potassium pump determined in three different states. Nat Commun 2022; 13:3957. [PMID: 35803952 PMCID: PMC9270386 DOI: 10.1038/s41467-022-31602-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Accepted: 06/24/2022] [Indexed: 11/09/2022] Open
Abstract
Sodium-Potassium Pump (Na+/K+-ATPase, NKA) is an ion pump that generates an electrochemical gradient of sodium and potassium ions across the plasma membrane by hydrolyzing ATP. During each Post-Albers cycle, NKA exchanges three cytoplasmic sodium ions for two extracellular potassium ions through alternating changes between the E1 and E2 states. Hitherto, several steps remained unknown during the complete working cycle of NKA. Here, we report cryo-electron microscopy (cryo-EM) structures of recombinant human NKA (hNKA) in three distinct states at 2.7–3.2 Å resolution, representing the E1·3Na and E1·3Na·ATP states with cytosolic gates open and the basic E2·[2K] state, respectively. This work provides the insights into the cytoplasmic Na+ entrance pathway and the mechanism of cytoplasmic gate closure coupled with ATP hydrolysis, filling crucial gaps in the structural elucidation of the Post-Albers cycle of NKA. Sodium-Potassium Pump (Na+/K+-ATPase, NKA) generates an electrochemical gradient of sodium and potassium ions across the plasma membrane by hydrolyzing ATP. Here, the authors report structures of human NKA providing insight into the cytoplasmic Na+ entrance and the cytoplasmic gate closure coupled to ATP hydrolysis.
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Affiliation(s)
- Yingying Guo
- Westlake Laboratory of Life Sciences and Biomedicine, Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, 18 Shilongshan Road, Hangzhou, 310024, Zhejiang Province, China.,Institute of Biology, Westlake Institute for Advanced Study, 18 Shilongshan Road, Hangzhou, 310024, Zhejiang Province, China.,Department of Biochemistry, School of Medicine, Southern University of Science and Technology, Shenzhen, Guangdong, China
| | - Yuanyuan Zhang
- Westlake Laboratory of Life Sciences and Biomedicine, Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, 18 Shilongshan Road, Hangzhou, 310024, Zhejiang Province, China.,Institute of Biology, Westlake Institute for Advanced Study, 18 Shilongshan Road, Hangzhou, 310024, Zhejiang Province, China
| | - Renhong Yan
- Westlake Laboratory of Life Sciences and Biomedicine, Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, 18 Shilongshan Road, Hangzhou, 310024, Zhejiang Province, China.,Institute of Biology, Westlake Institute for Advanced Study, 18 Shilongshan Road, Hangzhou, 310024, Zhejiang Province, China.,Department of Biochemistry, School of Medicine, Southern University of Science and Technology, Shenzhen, Guangdong, China
| | - Bangdong Huang
- Westlake Laboratory of Life Sciences and Biomedicine, Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, 18 Shilongshan Road, Hangzhou, 310024, Zhejiang Province, China.,Institute of Biology, Westlake Institute for Advanced Study, 18 Shilongshan Road, Hangzhou, 310024, Zhejiang Province, China
| | - Fangfei Ye
- Westlake Laboratory of Life Sciences and Biomedicine, Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, 18 Shilongshan Road, Hangzhou, 310024, Zhejiang Province, China.,Institute of Biology, Westlake Institute for Advanced Study, 18 Shilongshan Road, Hangzhou, 310024, Zhejiang Province, China
| | - Liushu Wu
- Westlake Laboratory of Life Sciences and Biomedicine, Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, 18 Shilongshan Road, Hangzhou, 310024, Zhejiang Province, China.,Institute of Biology, Westlake Institute for Advanced Study, 18 Shilongshan Road, Hangzhou, 310024, Zhejiang Province, China
| | - Ximin Chi
- Westlake Laboratory of Life Sciences and Biomedicine, Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, 18 Shilongshan Road, Hangzhou, 310024, Zhejiang Province, China.,Institute of Biology, Westlake Institute for Advanced Study, 18 Shilongshan Road, Hangzhou, 310024, Zhejiang Province, China
| | - Yi Shi
- Westlake Laboratory of Life Sciences and Biomedicine, Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, 18 Shilongshan Road, Hangzhou, 310024, Zhejiang Province, China.,Institute of Biology, Westlake Institute for Advanced Study, 18 Shilongshan Road, Hangzhou, 310024, Zhejiang Province, China
| | - Qiang Zhou
- Westlake Laboratory of Life Sciences and Biomedicine, Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, 18 Shilongshan Road, Hangzhou, 310024, Zhejiang Province, China. .,Institute of Biology, Westlake Institute for Advanced Study, 18 Shilongshan Road, Hangzhou, 310024, Zhejiang Province, China.
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7
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Sweet ME, Zhang X, Erdjument-Bromage H, Dubey V, Khandelia H, Neubert TA, Pedersen BP, Stokes DL. Serine phosphorylation regulates the P-type potassium pump KdpFABC. eLife 2020; 9:55480. [PMID: 32955430 PMCID: PMC7535926 DOI: 10.7554/elife.55480] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2020] [Accepted: 09/19/2020] [Indexed: 12/22/2022] Open
Abstract
KdpFABC is an ATP-dependent K+ pump that ensures bacterial survival in K+-deficient environments. Whereas transcriptional activation of kdpFABC expression is well studied, a mechanism for down-regulation when K+ levels are restored has not been described. Here, we show that KdpFABC is inhibited when cells return to a K+-rich environment. The mechanism of inhibition involves phosphorylation of Ser162 on KdpB, which can be reversed in vitro by treatment with serine phosphatase. Mutating Ser162 to Alanine produces constitutive activity, whereas the phosphomimetic Ser162Asp mutation inactivates the pump. Analyses of the transport cycle show that serine phosphorylation abolishes the K+-dependence of ATP hydrolysis and blocks the catalytic cycle after formation of the aspartyl phosphate intermediate (E1~P). This regulatory mechanism is unique amongst P-type pumps and this study furthers our understanding of how bacteria control potassium homeostasis to maintain cell volume and osmotic potential.
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Affiliation(s)
- Marie E Sweet
- Skirball Institute, Dept. of Cell Biology, New York University School of Medicine, New York, United States
| | - Xihui Zhang
- Skirball Institute, Dept. of Cell Biology, New York University School of Medicine, New York, United States
| | - Hediye Erdjument-Bromage
- Skirball Institute, Dept. of Cell Biology, New York University School of Medicine, New York, United States
| | - Vikas Dubey
- PHYLIFE, Physical Life Science, Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Odense, Denmark
| | - Himanshu Khandelia
- PHYLIFE, Physical Life Science, Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Odense, Denmark
| | - Thomas A Neubert
- Skirball Institute, Dept. of Cell Biology, New York University School of Medicine, New York, United States
| | - Bjørn P Pedersen
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - David L Stokes
- Skirball Institute, Dept. of Cell Biology, New York University School of Medicine, New York, United States
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8
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Structural dynamics of P-type ATPase ion pumps. Biochem Soc Trans 2020; 47:1247-1257. [PMID: 31671180 DOI: 10.1042/bst20190124] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Revised: 09/06/2019] [Accepted: 09/16/2019] [Indexed: 02/04/2023]
Abstract
P-type ATPases transport ions across biological membranes against concentration gradients and are essential for all cells. They use the energy from ATP hydrolysis to propel large intramolecular movements, which drive vectorial transport of ions. Tight coordination of the motions of the pump is required to couple the two spatially distant processes of ion binding and ATP hydrolysis. Here, we review our current understanding of the structural dynamics of P-type ATPases, focusing primarily on Ca2+ pumps. We integrate different types of information that report on structural dynamics, primarily time-resolved fluorescence experiments including single-molecule Förster resonance energy transfer and molecular dynamics simulations, and interpret them in the framework provided by the numerous crystal structures of sarco/endoplasmic reticulum Ca2+-ATPase. We discuss the challenges in characterizing the dynamics of membrane pumps, and the likely impact of new technologies on the field.
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9
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Nguyen TT, Sabat G, Sussman MR. In vivo cross-linking supports a head-to-tail mechanism for regulation of the plant plasma membrane P-type H +-ATPase. J Biol Chem 2018; 293:17095-17106. [PMID: 30217814 DOI: 10.1074/jbc.ra118.003528] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Revised: 08/30/2018] [Indexed: 11/06/2022] Open
Abstract
In higher plants, a P-type proton-pumping ATPase generates the proton-motive force essential for the function of all other transporters and for proper growth and development. X-ray crystallographic studies of the plant plasma membrane proton pump have provided information on amino acids involved in ATP catalysis but provided no information on the structure of the C-terminal regulatory domain. Despite progress in elucidating enzymes involved in the signaling pathways that activate or inhibit this pump, the site of interaction of the C-terminal regulatory domain with the catalytic domains remains a mystery. Genetic studies have pointed to amino acids in various parts of the protein that may be involved, but direct chemical evidence for which ones are specifically interacting with the C terminus is lacking. In this study, we used in vivo cross-linking experiments with a photoreactive unnatural amino acid, p-benzoylphenylalanine, and tandem MS to obtain direct evidence that the C-terminal regulatory domain interacts with amino acids located within the N-terminal actuator domain. Our observations are consistent with a mechanism in which intermolecular, rather than intramolecular, interactions are involved. Our model invokes a "head-to-tail" organization of ATPase monomers in which the C-terminal domain of one ATPase molecule interacts with the actuator domain of another ATPase molecule. This model serves to explain why cross-linked peptides are found only in dimers and trimers, and it is consistent with prior studies suggesting that within the membrane the protein can be organized as homopolymers, including dimers, trimers, and hexamers.
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Affiliation(s)
- Thao T Nguyen
- From the Biotechnology Center and.,Biochemistry Department, University of Wisconsin-Madison, Madison, Wisconsin 53706
| | | | - Michael R Sussman
- From the Biotechnology Center and .,Biochemistry Department, University of Wisconsin-Madison, Madison, Wisconsin 53706
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10
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Characterization of ATP7A missense mutants suggests a correlation between intracellular trafficking and severity of Menkes disease. Sci Rep 2017; 7:757. [PMID: 28389643 PMCID: PMC5428812 DOI: 10.1038/s41598-017-00618-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Accepted: 03/06/2017] [Indexed: 12/12/2022] Open
Abstract
Menkes disease (MD) is caused by mutations in ATP7A, encoding a copper-transporting P-type ATPase which exhibits copper-dependent trafficking. ATP7A is found in the Trans-Golgi Network (TGN) at low copper concentrations, and in the post-Golgi compartments and the plasma membrane at higher concentrations. Here we have analyzed the effect of 36 ATP7A missense mutations identified in phenotypically different MD patients. Nine mutations identified in patients with severe MD, virtually eliminated ATP7A synthesis, in most cases due to aberrant RNA splicing. A group of 21 predominantly severe mutations led to trapping of the protein in TGN and displayed essentially no activity in a yeast-based functional assay. These were predicted to inhibit the catalytic phosphorylation of the protein. Four mutants showed diffuse post-TGN localization, while two displayed copper dependent trafficking. These six variants were identified in patients with mild MD and typically displayed activity in the yeast assay. The four post-TGN located mutants were presumably affected in the catalytic dephosphorylation of the protein. Together these results indicate that the severity of MD correlate with cellular localization of ATP7A and support previous studies indicating that phosphorylation is crucial for the exit of ATP7A from TGN, while dephosphorylation is crucial for recycling back to TGN.
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11
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Das A, Rui H, Nakamoto R, Roux B. Conformational Transitions and Alternating-Access Mechanism in the Sarcoplasmic Reticulum Calcium Pump. J Mol Biol 2017; 429:647-666. [PMID: 28093226 PMCID: PMC5467534 DOI: 10.1016/j.jmb.2017.01.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Revised: 12/31/2016] [Accepted: 01/08/2017] [Indexed: 11/22/2022]
Abstract
Ion pumps are integral membrane proteins responsible for transporting ions against concentration gradients across biological membranes. Sarco/endoplasmic reticulum Ca2+-ATPase (SERCA), a member of the P-type ATPases family, transports two calcium ions per hydrolyzed ATP molecule via an "alternating-access" mechanism. High-resolution crystallographic structures provide invaluable insight on the structural mechanism of the ion pumping process. However, to understand the molecular details of how ATP hydrolysis is coupled to calcium transport, it is necessary to gain knowledge about the conformational transition pathways connecting the crystallographically resolved conformations. Large-scale transitions in SERCA occur at time-scales beyond the current reach of unbiased molecular dynamics simulations. Here, we overcome this challenge by employing the string method, which represents a transition pathway as a chainofstates linking two conformational endpoints. Using a multiscale methodology, we have determined all-atom transition pathways for three main conformational transitions responsible for the alternating-access mechanism. The present pathways provide a clear chronology and ordering of the key events underlying the active transport of calcium ions by SERCA. Important conclusions are that the conformational transition that leads to occlusion with bound ATP and calcium is highly concerted and cooperative, the phosphorylation of Asp351 causes areorganization of the cytoplasmic domains that subsequently drives the opening of the luminal gate, and thereclosing of luminal gate induces a shift in the cytoplasmic domains that subsequently enables the dephosphorylation of Asp351-P. Formation of transient residue-residue contacts along the conformational transitions predicted by the computations provide an experimental route to test the general validity of the computational pathways.
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Affiliation(s)
- Avisek Das
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57(th) Street, Chicago,IL 60637, USA
| | - Huan Rui
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57(th) Street, Chicago,IL 60637, USA
| | - Robert Nakamoto
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, PO Box 800886, 480Ray C. Hunt Drive, Charlottesville, VA 22908, USA
| | - Benoît Roux
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57(th) Street, Chicago,IL 60637, USA.
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12
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Holm R, Toustrup-Jensen MS, Einholm AP, Schack VR, Andersen JP, Vilsen B. Neurological disease mutations of α3 Na +,K +-ATPase: Structural and functional perspectives and rescue of compromised function. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2016; 1857:1807-1828. [PMID: 27577505 DOI: 10.1016/j.bbabio.2016.08.009] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2016] [Revised: 08/19/2016] [Accepted: 08/25/2016] [Indexed: 11/26/2022]
Abstract
Na+,K+-ATPase creates transmembrane ion gradients crucial to the function of the central nervous system. The α-subunit of Na+,K+-ATPase exists as four isoforms (α1-α4). Several neurological phenotypes derive from α3 mutations. The effects of some of these mutations on Na+,K+-ATPase function have been studied in vitro. Here we discuss the α3 disease mutations as well as information derived from studies of corresponding mutations of α1 in the light of the high-resolution crystal structures of the Na+,K+-ATPase. A high proportion of the α3 disease mutations occur in the transmembrane sector and nearby regions essential to Na+ and K+ binding. In several cases the compromised function can be traced to disturbance of the Na+ specific binding site III. Recently, a secondary mutation was found to rescue the defective Na+ binding caused by a disease mutation. A perspective is that it may be possible to develop an efficient pharmaceutical mimicking the rescuing effect.
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Affiliation(s)
- Rikke Holm
- Department of Biomedicine, Aarhus University, 8000 Aarhus C, Denmark.
| | | | - Anja P Einholm
- Department of Biomedicine, Aarhus University, 8000 Aarhus C, Denmark.
| | - Vivien R Schack
- Department of Biomedicine, Aarhus University, 8000 Aarhus C, Denmark.
| | - Jens P Andersen
- Department of Biomedicine, Aarhus University, 8000 Aarhus C, Denmark.
| | - Bente Vilsen
- Department of Biomedicine, Aarhus University, 8000 Aarhus C, Denmark.
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13
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Azouaoui H, Montigny C, Ash MR, Fijalkowski F, Jacquot A, Grønberg C, López-Marqués RL, Palmgren MG, Garrigos M, le Maire M, Decottignies P, Gourdon P, Nissen P, Champeil P, Lenoir G. A high-yield co-expression system for the purification of an intact Drs2p-Cdc50p lipid flippase complex, critically dependent on and stabilized by phosphatidylinositol-4-phosphate. PLoS One 2014; 9:e112176. [PMID: 25393116 PMCID: PMC4230938 DOI: 10.1371/journal.pone.0112176] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Accepted: 10/13/2014] [Indexed: 01/01/2023] Open
Abstract
P-type ATPases from the P4 subfamily (P4-ATPases) are energy-dependent transporters, which are thought to establish lipid asymmetry in eukaryotic cell membranes. Together with their Cdc50 accessory subunits, P4-ATPases couple ATP hydrolysis to lipid transport from the exoplasmic to the cytoplasmic leaflet of plasma membranes, late Golgi membranes, and endosomes. To gain insights into the structure and function of these important membrane pumps, robust protocols for expression and purification are required. In this report, we present a procedure for high-yield co-expression of a yeast flippase, the Drs2p-Cdc50p complex. After recovery of yeast membranes expressing both proteins, efficient purification was achieved in a single step by affinity chromatography on streptavidin beads, yielding ∼1–2 mg purified Drs2p-Cdc50p complex per liter of culture. Importantly, the procedure enabled us to recover a fraction that mainly contained a 1∶1 complex, which was assessed by size-exclusion chromatography and mass spectrometry. The functional properties of the purified complex were examined, including the dependence of its catalytic cycle on specific lipids. The dephosphorylation rate was stimulated in the simultaneous presence of the transported substrate, phosphatidylserine (PS), and the regulatory lipid phosphatidylinositol-4-phosphate (PI4P), a phosphoinositide that plays critical roles in membrane trafficking events from the trans-Golgi network (TGN). Likewise, overall ATP hydrolysis by the complex was critically dependent on the simultaneous presence of PI4P and PS. We also identified a prominent role for PI4P in stabilization of the Drs2p-Cdc50p complex towards temperature- or C12E8-induced irreversible inactivation. These results indicate that the Drs2p-Cdc50p complex remains functional after affinity purification and that PI4P as a cofactor tightly controls its stability and catalytic activity. This work offers appealing perspectives for detailed structural and functional characterization of the Drs2p-Cdc50p lipid transport mechanism.
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Affiliation(s)
- Hassina Azouaoui
- Univ Paris-Sud, UMR 8221, Orsay, France
- CEA, iBiTec-S (Institut de Biologie et de Technologies de Saclay), SBSM (Service de Bioénergétique, Biologie Structurale et Mécanismes), Laboratoire des Protéines Membranaires, Gif-sur-Yvette, France
- CNRS, UMR 8221, Gif-sur-Yvette, France
| | - Cédric Montigny
- Univ Paris-Sud, UMR 8221, Orsay, France
- CEA, iBiTec-S (Institut de Biologie et de Technologies de Saclay), SBSM (Service de Bioénergétique, Biologie Structurale et Mécanismes), Laboratoire des Protéines Membranaires, Gif-sur-Yvette, France
- CNRS, UMR 8221, Gif-sur-Yvette, France
| | - Miriam-Rose Ash
- Centre for Membrane Pumps in Cells and Disease – PUMPKIN, Danish National Research Foundation, Aarhus, Denmark
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - Frank Fijalkowski
- Centre for Membrane Pumps in Cells and Disease – PUMPKIN, Danish National Research Foundation, Aarhus, Denmark
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - Aurore Jacquot
- Univ Paris-Sud, UMR 8221, Orsay, France
- CEA, iBiTec-S (Institut de Biologie et de Technologies de Saclay), SBSM (Service de Bioénergétique, Biologie Structurale et Mécanismes), Laboratoire des Protéines Membranaires, Gif-sur-Yvette, France
- CNRS, UMR 8221, Gif-sur-Yvette, France
| | - Christina Grønberg
- Centre for Membrane Pumps in Cells and Disease – PUMPKIN, Danish National Research Foundation, Aarhus, Denmark
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - Rosa L. López-Marqués
- Centre for Membrane Pumps in Cells and Disease – PUMPKIN, Danish National Research Foundation, Aarhus, Denmark
- Department of Plant and Environmental Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Michael G. Palmgren
- Centre for Membrane Pumps in Cells and Disease – PUMPKIN, Danish National Research Foundation, Aarhus, Denmark
- Department of Plant and Environmental Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Manuel Garrigos
- Univ Paris-Sud, UMR 8221, Orsay, France
- CEA, iBiTec-S (Institut de Biologie et de Technologies de Saclay), SBSM (Service de Bioénergétique, Biologie Structurale et Mécanismes), Laboratoire des Protéines Membranaires, Gif-sur-Yvette, France
- CNRS, UMR 8221, Gif-sur-Yvette, France
| | - Marc le Maire
- Univ Paris-Sud, UMR 8221, Orsay, France
- CEA, iBiTec-S (Institut de Biologie et de Technologies de Saclay), SBSM (Service de Bioénergétique, Biologie Structurale et Mécanismes), Laboratoire des Protéines Membranaires, Gif-sur-Yvette, France
- CNRS, UMR 8221, Gif-sur-Yvette, France
| | - Paulette Decottignies
- CNRS, Institut de Biochimie et Biophysique Moléculaire et Cellulaire, UMR 8619, Orsay, France
- Univ Paris-Sud, Orsay, France
| | - Pontus Gourdon
- Centre for Membrane Pumps in Cells and Disease – PUMPKIN, Danish National Research Foundation, Aarhus, Denmark
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - Poul Nissen
- Centre for Membrane Pumps in Cells and Disease – PUMPKIN, Danish National Research Foundation, Aarhus, Denmark
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - Philippe Champeil
- Univ Paris-Sud, UMR 8221, Orsay, France
- CEA, iBiTec-S (Institut de Biologie et de Technologies de Saclay), SBSM (Service de Bioénergétique, Biologie Structurale et Mécanismes), Laboratoire des Protéines Membranaires, Gif-sur-Yvette, France
- CNRS, UMR 8221, Gif-sur-Yvette, France
| | - Guillaume Lenoir
- Univ Paris-Sud, UMR 8221, Orsay, France
- CEA, iBiTec-S (Institut de Biologie et de Technologies de Saclay), SBSM (Service de Bioénergétique, Biologie Structurale et Mécanismes), Laboratoire des Protéines Membranaires, Gif-sur-Yvette, France
- CNRS, UMR 8221, Gif-sur-Yvette, France
- * E-mail:
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14
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Clausen JD, Holdensen AN, Andersen JP. Critical roles of interdomain interactions for modulatory ATP binding to sarcoplasmic reticulum Ca2+-ATPase. J Biol Chem 2014; 289:29123-34. [PMID: 25193668 DOI: 10.1074/jbc.m114.571687] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
ATP has dual roles in the reaction cycle of sarcoplasmic reticulum Ca(2+)-ATPase. Upon binding to the Ca2E1 state, ATP phosphorylates the enzyme, and by binding to other conformational states in a non-phosphorylating modulatory mode ATP stimulates the dephosphorylation and other partial reaction steps of the cycle, thereby ensuring a high rate of Ca(2+) transport under physiological conditions. The present study elucidates the mechanism underlying the modulatory effect on dephosphorylation. In the intermediate states of dephosphorylation the A-domain residues Ser(186) and Asp(203) interact with Glu(439) (N-domain) and Arg(678) (P-domain), respectively. Single mutations to these residues abolish the stimulation of dephosphorylation by ATP. The double mutation swapping Asp(203) and Arg(678) rescues ATP stimulation, whereas this is not the case for the double mutation swapping Ser(186) and Glu(439). By taking advantage of the ability of wild type and mutant Ca(2+)-ATPases to form stable complexes with aluminum fluoride (E2·AlF) and beryllium fluoride (E2·BeF) as analogs of the E2·P phosphoryl transition state and E2P ground state, respectively, of the dephosphorylation reaction, the mutational effects on ATP binding to these intermediates are demonstrated. In the wild type Ca(2+)-ATPase, the ATP affinity of the E2·P phosphoryl transition state is higher than that of the E2P ground state, thus explaining the stimulation of dephosphorylation by nucleotide-induced transition state stabilization. We find that the Asp(203)-Arg(678) and Ser(186)-Glu(439) interdomain bonds are critical, because they tighten the interaction with ATP in the E2·P phosphoryl transition state. Moreover, ATP binding and the Ser(186)-Glu(439) bond are mutually exclusive in the E2P ground state.
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Affiliation(s)
- Johannes D Clausen
- From the Department of Biomedicine, Aarhus University, DK-8000 Aarhus C, Denmark, and the Centre for Membrane Pumps in Cells and Disease-PUMPKIN, Danish National Research Foundation, Department of Molecular Biology and Genetics, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Anne Nyholm Holdensen
- From the Department of Biomedicine, Aarhus University, DK-8000 Aarhus C, Denmark, and the Centre for Membrane Pumps in Cells and Disease-PUMPKIN, Danish National Research Foundation, Department of Molecular Biology and Genetics, Aarhus University, DK-8000 Aarhus C, Denmark
| | - Jens Peter Andersen
- From the Department of Biomedicine, Aarhus University, DK-8000 Aarhus C, Denmark, and
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15
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Lipid flippase modulates olfactory receptor expression and odorant sensitivity in Drosophila. Proc Natl Acad Sci U S A 2014; 111:7831-6. [PMID: 24821794 DOI: 10.1073/pnas.1401938111] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
In Drosophila melanogaster, the male-specific pheromone cVA (11-cis-vaccenyl acetate) functions as a sex-specific social cue. However, our understanding of the molecular mechanisms underlying cVA pheromone transduction and its regulation are incomplete. Using a genetic screen combined with an electrophysiological assay to monitor pheromone-evoked activity in the cVA-sensing Or67d neurons, we identified an olfactory sensitivity factor encoded by the dATP8B gene, the Drosophila homolog of mammalian ATP8B. dATP8B is expressed in all olfactory neurons that express Orco, the odorant receptor coreceptor, and the odorant responses in most Orco-expressing neurons are reduced. Or67d neurons are severely affected, with strongly impaired cVA-induced responses and lacking spontaneous spiking in the mutants. The dATP8B locus encodes a member of the P4-type ATPase family thought to flip aminophospholipids such as phosphatidylserine and phosphatidylethanolamine from one membrane leaflet to the other. dATP8B protein is concentrated in the cilia of olfactory neuron dendrites, the site of odorant transduction. Focusing on Or67d neuron function, we show that Or67d receptors are mislocalized in dATP8B mutants and that cVA responses can be restored to dATP8B mutants by misexpressing a wild-type dATP8B rescuing transgene, by expressing a vertebrate P4-type ATPase member in the pheromone-sensing neurons or by overexpressing Or67d receptor subunits. These findings reveal an unexpected role for lipid translocation in olfactory receptor expression and sensitivity to volatile odorants.
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16
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SERCA mutant E309Q binds two Ca(2+) ions but adopts a catalytically incompetent conformation. EMBO J 2013; 32:3231-43. [PMID: 24270570 DOI: 10.1038/emboj.2013.250] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Accepted: 10/21/2013] [Indexed: 11/08/2022] Open
Abstract
The sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) couples ATP hydrolysis to transport of Ca(2+). This directed energy transfer requires cross-talk between the two Ca(2+) sites and the phosphorylation site over 50 Å distance. We have addressed the mechano-structural basis for this intramolecular signal by analysing the structure and the functional properties of SERCA mutant E309Q. Glu(309) contributes to Ca(2+) coordination at site II, and a consensus has been that E309Q only binds Ca(2+) at site I. The crystal structure of E309Q in the presence of Ca(2+) and an ATP analogue, however, reveals two occupied Ca(2+) sites of a non-catalytic Ca2E1 state. Ca(2+) is bound with micromolar affinity by both Ca(2+) sites in E309Q, but without cooperativity. The Ca(2+)-bound mutant does phosphorylate from ATP, but at a very low maximal rate. Phosphorylation depends on the correct positioning of the A-domain, requiring a shift of transmembrane segment M1 into an 'up and kinked position'. This transition is impaired in the E309Q mutant, most likely due to a lack of charge neutralization and altered hydrogen binding capacities at Ca(2+) site II.
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17
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Rudbeck ME, Blomberg MRA, Barth A. Hydrolysis of the E2P Phosphoenzyme of the Ca2+-ATPase: A Theoretical Study. J Phys Chem B 2013; 117:9224-32. [DOI: 10.1021/jp4049814] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Maria E. Rudbeck
- Department of Biochemistry and
Biophysics, Arrhenius Laboratories, Stockholm University, 10691 Stockholm, Sweden
| | - Margareta R. A. Blomberg
- Department of Organic Chemistry,
Arrhenius Laboratories, Stockholm University, 10691 Stockholm, Sweden
| | - Andreas Barth
- Department of Biochemistry and
Biophysics, Arrhenius Laboratories, Stockholm University, 10691 Stockholm, Sweden
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18
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Sørensen DM, Møller AB, Jakobsen MK, Jensen MK, Vangheluwe P, Buch-Pedersen MJ, Palmgren MG. Ca2+ induces spontaneous dephosphorylation of a novel P5A-type ATPase. J Biol Chem 2012; 287:28336-48. [PMID: 22730321 DOI: 10.1074/jbc.m112.387191] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
P5 ATPases constitute the least studied group of P-type ATPases, an essential family of ion pumps in all kingdoms of life. Although P5 ATPases are present in every eukaryotic genome analyzed so far, they have remained orphan pumps, and their biochemical function is obscure. We show that a P5A ATPase from barley, HvP5A1, locates to the endoplasmic reticulum and is able to rescue knock-out mutants of P5A genes in both Arabidopsis thaliana and Saccharomyces cerevisiae. HvP5A1 spontaneously forms a phosphorylated reaction cycle intermediate at the catalytic residue Asp-488, whereas, among all plant nutrients tested, only Ca(2+) triggers dephosphorylation. Remarkably, Ca(2+)-induced dephosphorylation occurs at high apparent [Ca(2+)] (K(i) = 0.25 mM) and is independent of the phosphatase motif of the pump and the putative binding site for transported ligands located in M4. Taken together, our results rule out that Ca(2+) is a transported substrate but indicate the presence of a cytosolic low affinity Ca(2+)-binding site, which is conserved among P-type pumps and could be involved in pump regulation. Our work constitutes the first characterization of a P5 ATPase phosphoenzyme and points to Ca(2+) as a modifier of its function.
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Affiliation(s)
- Danny Mollerup Sørensen
- Centre for Membrane Pumps in Cells and Disease, PUMPKIN, Danish National Research Foundation, Department of Plant Biology and Biotechnology, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark
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19
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Nagarajan A, Andersen JP, Woolf TB. Coarse-grained simulations of transitions in the E2-to-E1 conformations for Ca ATPase (SERCA) show entropy-enthalpy compensation. J Mol Biol 2012; 422:575-93. [PMID: 22684148 DOI: 10.1016/j.jmb.2012.06.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Revised: 04/23/2012] [Accepted: 06/01/2012] [Indexed: 10/28/2022]
Abstract
SERCA is a membrane transport protein that has been extensively studied. There are a large number of highly resolved X-ray structures and several hundred mutations that have been characterized functionally. Despite this, the molecular details of the catalytic cycle, a cycle that includes large conformational changes, is not fully understood. In this computational study, we provide molecular dynamics descriptions of conformational changes during the E2→E1 transitions. The motivating point for these calculations was a series of insertion mutants in the A-M3 linker region that led to significant shifts in measured rates between the E2 and E1 states, as shown by experimental characterization. Using coarse-grained dynamic importance sampling within the context of a population shift framework, we sample on the intermediates along the transition pathway to address the mechanism for the conformational changes and the effects of the insertion mutations on the kinetics of the transition. The calculations define an approximation for the relative changes in entropy and enthalpy along the transition. These are found to be important for understanding the experimentally observed differences in rates. In particular, the interactions between cytoplasmic domains, water interactions, and the shifts in protein degrees of freedom with the insertion mutations show mutual compensation for the E2→E1 transitions in wild-type and mutant systems.
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Affiliation(s)
- Anu Nagarajan
- Department of Physiology, Johns Hopkins University, School of Medicine, Biophysics 206, Baltimore, MD 21205, USA.
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20
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Nagarajan A, Andersen JP, Woolf TB. The role of domain: domain interactions versus domain: water interactions in the coarse-grained simulations of the E1P to E2P transitions in Ca-ATPase (SERCA). Proteins 2012; 80:1929-47. [PMID: 22422644 DOI: 10.1002/prot.24070] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2011] [Revised: 02/24/2012] [Accepted: 03/03/2012] [Indexed: 12/15/2022]
Abstract
SERCA is an important model system for understanding the molecular details of conformational change in membrane transport systems. This reflects the large number of solved X-ray structures and the equally large database of mutations that have been assayed. In this computational study, we provide a molecular dynamics description of the conformational changes during the E1P → E2P transitions. This set of states further changes with insertion mutants in the A-M3 linker region. These mutants were experimentally shown to lead to significant shifts in rates between the E1P → E2P states. Using the population shift framework and dynamic importance sampling method along with coarse-grained representations of the protein, lipid, and water, we suggest why these changes are found. The calculations sample on intermediates and suggest that changes in interactions, individual helix interactions, and water behavior are key elements in the molecular compositions that underlie shifts in kinetics. In particular, as the insertion length grows, it attracts more water and disrupts domain interactions, creating changes as well at the sites of key helix interactions between the A-Domain and the P-Domain. This provides a conceptual picture that aids understanding of the experimental results.
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Affiliation(s)
- Anu Nagarajan
- Department of Physiology, School of Medicine, Johns Hopkins University, Baltimore, Maryland 21205, USA.
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21
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Jacquot A, Montigny C, Hennrich H, Barry R, le Maire M, Jaxel C, Holthuis J, Champeil P, Lenoir G. Phosphatidylserine stimulation of Drs2p·Cdc50p lipid translocase dephosphorylation is controlled by phosphatidylinositol-4-phosphate. J Biol Chem 2012; 287:13249-61. [PMID: 22351780 DOI: 10.1074/jbc.m111.313916] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Here, Drs2p, a yeast lipid translocase that belongs to the family of P(4)-type ATPases, was overexpressed in the yeast Saccharomyces cerevisiae together with Cdc50p, its glycosylated partner, as a result of the design of a novel co-expression vector. The resulting high yield allowed us, using crude membranes or detergent-solubilized membranes, to measure the formation from [γ-(32)P]ATP of a (32)P-labeled transient phosphoenzyme at the catalytic site of Drs2p. Formation of this phosphoenzyme could be detected only if Cdc50p was co-expressed with Drs2p but was not dependent on full glycosylation of Cdc50p. It was inhibited by orthovanadate and fluoride compounds. In crude membranes, the phosphoenzyme formed at steady state at 4 °C displayed ADP-insensitive but temperature-sensitive decay. Solubilizing concentrations of dodecyl maltoside left this decay rate almost unaltered, whereas several other detergents accelerated it. Unexpectedly, the dephosphorylation rate for the solubilized Drs2p·Cdc50p complex was inhibited by the addition of phosphatidylserine. Phosphatidylserine exerted its anticipated accelerating effect on the dephosphorylation of Drs2p·Cdc50p complex only in the additional presence of phosphatidylinositol-4-phosphate. These results explain why phosphatidylinositol-4-phosphate tightly controls Drs2p-catalyzed lipid transport and establish the functional relevance of the Drs2p·Cdc50p complex overexpressed here.
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Affiliation(s)
- Aurore Jacquot
- UMR 8221 (Systèmes Membranaires, Photobiologie, Stress et Détoxication), CNRS, Gif-sur-Yvette, France
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22
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Critical role of a transmembrane lysine in aminophospholipid transport by mammalian photoreceptor P4-ATPase ATP8A2. Proc Natl Acad Sci U S A 2012; 109:1449-54. [PMID: 22307598 DOI: 10.1073/pnas.1108862109] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
ATP8A2 is a P(4)-ATPase ("flippase") located in membranes of retinal photoreceptors, brain cells, and testis, where it mediates transport of aminophospholipids toward the cytoplasmic leaflet. It has long been an enigma whether the mechanism of P(4)-ATPases resembles that of the well-characterized cation-transporting P-type ATPases, and it is unknown whether the flippases interact directly with the lipid and with counterions. Our results demonstrate that ATP8A2 forms a phosphoenzyme intermediate at the conserved aspartate (Asp(416)) in the P-type ATPase signature sequence and exists in E(1)P and E(2)P forms similar to the archetypical P-type ATPases. Using the properties of the phosphoenzyme, the partial reaction steps of the transport cycle were examined, and the roles of conserved residues Asp(196), Glu(198), Lys(873), and Asn(874) in the transport mechanism were elucidated. The former two residues in the A-domain T/D-G-E-S/T motif are involved in catalysis of E(2)P dephosphorylation, the glutamate being essential. Transported aminophospholipids activate the dephosphorylation similar to K(+) activation of dephosphorylation in Na(+),K(+)-ATPase. Lys(873) mutants (particularly K873A and K873E) display a markedly reduced sensitivity to aminophospholipids. Hence, Lys(873), located in transmembrane segment M5 at a "hot spot" for cation binding in Ca(2+)-ATPase and Na(+),K(+)-ATPase, appears to participate directly in aminophospholipid binding or to mediate a crucial interaction within the ATP8A2-CDC50 complex. By contrast, Lys(865) is unimportant for aminophospholipid sensitivity. Binding of Na(+), H(+), K(+), Cl(-), or Ca(2+) to the E(1) form as a counterion is not required for activation of phosphorylation from ATP. Therefore, phospholipids could be the only substrate transported by ATP8A2.
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23
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Abstract
The sarcoplasmic (SERCA 1a) Ca2+-ATPase is a membrane protein abundantly present in skeletal muscles where it functions as an indispensable component of the excitation-contraction coupling, being at the expense of ATP hydrolysis involved in Ca2+/H+ exchange with a high thermodynamic efficiency across the sarcoplasmic reticulum membrane. The transporter serves as a prototype of a whole family of cation transporters, the P-type ATPases, which in addition to Ca2+ transporting proteins count Na+, K+-ATPase and H+, K+-, proton- and heavy metal transporting ATPases as prominent members. The ability in recent years to produce and analyze at atomic (2·3-3 Å) resolution 3D-crystals of Ca2+-transport intermediates of SERCA 1a has meant a breakthrough in our understanding of the structural aspects of the transport mechanism. We describe here the detailed construction of the ATPase in terms of one membraneous and three cytosolic domains held together by a central core that mediates coupling between Ca2+-transport and ATP hydrolysis. During turnover, the pump is present in two different conformational states, E1 and E2, with a preference for the binding of Ca2+ and H+, respectively. We discuss how phosphorylated and non-phosphorylated forms of these conformational states with cytosolic, occluded or luminally exposed cation-binding sites are able to convert the chemical energy derived from ATP hydrolysis into an electrochemical gradient of Ca2+ across the sarcoplasmic reticulum membrane. In conjunction with these basic reactions which serve as a structural framework for the transport function of other P-type ATPases as well, we also review the role of the lipid phase and the regulatory and thermodynamic aspects of the transport mechanism.
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24
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Clausen JD, McIntosh DB, Woolley DG, Andersen JP. Modulatory ATP binding affinity in intermediate states of E2P dephosphorylation of sarcoplasmic reticulum Ca2+-ATPase. J Biol Chem 2011; 286:11792-802. [PMID: 21288896 DOI: 10.1074/jbc.m110.206094] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The mechanism of ATP modulation of E2P dephosphorylation of sarcoplasmic reticulum Ca(2+)-ATPase wild type and mutant forms was examined in nucleotide binding studies of states analogous to the various intermediates of the dephosphorylation reaction, obtained by binding of metal fluorides, vanadate, or thapsigargin. Wild type Ca(2+)-ATPase displays an ATP affinity of 4 μM for the E2P ground state analog, 1 μM for the E2P transition state and product state analogs, and 11 μM for the E2 dephosphoenzyme. Hence, ATP binding stabilizes the transition and product states relative to the ground state, thereby explaining the accelerating effect of ATP on dephosphorylation. Replacement of Phe(487) (N-domain) with serine, Arg(560) (N-domain) with leucine, or Arg(174) (A-domain) with alanine or glutamate reduces ATP affinity in all E2/E2P intermediate states. Alanine substitution of Ile(188) (A-domain) increases the ATP affinity, although ATP acceleration of dephosphorylation is disrupted, thus indicating that the critical role of Ile(188) in ATP modulation is mechanistically based rather than being associated with the binding of nucleotide. Mutants with alanine replacement of Lys(205) (A-domain) or Glu(439) (N-domain) exhibit an anomalous inhibition by ATP of E2P dephosphorylation, due to ATP binding increasing the stability of the E2P ground state relative to the transition state. The ATP affinity of Ca(2)E2P, stabilized by inserting four glycines in the A-M1 linker, is similar to that of the E2P ground state, but the Ca(2+)-free E1 state of this mutant exhibits 3 orders of magnitude reduction of ATP affinity.
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Affiliation(s)
- Johannes D Clausen
- Department of Physiology and Biophysics, Aarhus University, Aarhus C, Denmark
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25
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Morth JP, Pedersen BP, Buch-Pedersen MJ, Andersen JP, Vilsen B, Palmgren MG, Nissen P. A structural overview of the plasma membrane Na+,K+-ATPase and H+-ATPase ion pumps. Nat Rev Mol Cell Biol 2011; 12:60-70. [PMID: 21179061 DOI: 10.1038/nrm3031] [Citation(s) in RCA: 244] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Plasma membrane ATPases are primary active transporters of cations that maintain steep concentration gradients. The ion gradients and membrane potentials derived from them form the basis for a range of essential cellular processes, in particular Na(+)-dependent and proton-dependent secondary transport systems that are responsible for uptake and extrusion of metabolites and other ions. The ion gradients are also both directly and indirectly used to control pH homeostasis and to regulate cell volume. The plasma membrane H(+)-ATPase maintains a proton gradient in plants and fungi and the Na(+),K(+)-ATPase maintains a Na(+) and K(+) gradient in animal cells. Structural information provides insight into the function of these two distinct but related P-type pumps.
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Affiliation(s)
- J Preben Morth
- Danish National Research Foundation, Centre for Membrane Pumps in Cells and Disease - PUMPKIN, Denmark
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26
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Yatime L, Laursen M, Morth JP, Esmann M, Nissen P, Fedosova NU. Structural insights into the high affinity binding of cardiotonic steroids to the Na+,K+-ATPase. J Struct Biol 2010; 174:296-306. [PMID: 21182963 DOI: 10.1016/j.jsb.2010.12.004] [Citation(s) in RCA: 128] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2010] [Revised: 12/13/2010] [Accepted: 12/15/2010] [Indexed: 02/08/2023]
Abstract
The Na+,K+-ATPase belongs to the P-ATPase family, whose characteristic property is the formation of a phosphorylated intermediate. The enzyme is also a defined target for cardiotonic steroids which inhibit its functional activity and initiate intracellular signaling. Here we describe the 4.6 Å resolution crystal structure of the pig kidney Na+,K+-ATPase in its phosphorylated form stabilized by high affinity binding of the cardiotonic steroid ouabain. The steroid binds to a site formed at transmembrane segments αM1-αM6, plugging the ion pathway from the extracellular side. This structure differs from the previously reported low affinity complex with potassium. Most importantly, the A domain has rotated in response to phosphorylation and αM1-2 move towards the ouabain molecule, providing for high affinity interactions and closing the ion pathway from the extracellular side. The observed re-arrangements of the Na+,K+-ATPase stabilized by cardiotonic steroids may affect protein-protein interactions within the intracellular signal transduction networks.
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Affiliation(s)
- Laure Yatime
- Centre for Membrane Pumps in Cells and Disease-PUMPKIN, Danish National Research Foundation, Denmark
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27
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Clausen JD, Andersen JP. Glutamate 90 at the luminal ion gate of sarcoplasmic reticulum Ca2+-ATPase is critical for Ca(2+) binding on both sides of the membrane. J Biol Chem 2010; 285:20780-92. [PMID: 20421308 DOI: 10.1074/jbc.m110.116459] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The roles of Ser(72), Glu(90), and Lys(297) at the luminal ends of transmembrane helices M1, M2, and M4 of sarcoplasmic reticulum Ca(2+)-ATPase were examined by transient and steady-state kinetic analysis of mutants. The dependence on the luminal Ca(2+) concentration of phosphorylation by P(i) ("Ca(2+) gradient-dependent E2P formation") showed a reduction of the apparent affinity for luminal Ca(2+) in mutants with alanine or leucine replacement of Glu(90), whereas arginine replacement of Glu(90) or Ser(72) allowed E2P formation from P(i) even at luminal Ca(2+) concentrations much too small to support phosphorylation in wild type. The latter mutants further displayed a blocked dephosphorylation of E2P and an increased rate of conversion of the ADP-sensitive E1P phosphoenzyme intermediate to ADP-insensitive E2P as well as insensitivity of the E2.BeF(3)(-) complex to luminal Ca(2+). Altogether, these findings, supported by structural modeling, indicate that the E2P intermediate is stabilized in the mutants with arginine replacement of Glu(90) or Ser(72), because the positive charge of the arginine side chain mimics Ca(2+) occupying a luminally exposed low affinity Ca(2+) site of E2P, thus identifying an essential locus (a "leaving site") on the luminal Ca(2+) exit pathway. Mutants with alanine or leucine replacement of Glu(90) further displayed a marked slowing of the Ca(2+) binding transition as well as slowing of the dissociation of Ca(2+) from Ca(2)E1 back toward the cytoplasm, thus demonstrating that Glu(90) is also critical for the function of the cytoplasmically exposed Ca(2+) sites on the opposite side of the membrane relative to where Glu(90) is located.
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Affiliation(s)
- Johannes D Clausen
- Centre for Membrane Pumps in Cells and Disease-PUMPKIN, Danish National Research Foundation, Department of Physiology and Biophysics, Aarhus University, DK-8000 Aarhus C, Denmark
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28
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Møller JV, Olesen C, Winther AML, Nissen P. What can be learned about the function of a single protein from its various X-ray structures: the example of the sarcoplasmic calcium pump. Methods Mol Biol 2010; 654:119-40. [PMID: 20665264 DOI: 10.1007/978-1-60761-762-4_7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Improvements in the handling of membrane proteins for crystallization, combined with better synchrotron sources for X-ray diffraction analysis, are leading to clarification of the structural details of an ever increasing number of membrane transporters and receptors. Here we describe how this development has resulted in the elucidation at atomic resolution of a large number of structures of the sarcoplasmic Ca(2+)-ATPase (SERCA1a) present in skeletal muscle. The structures corresponding to the various intermediary states have been obtained after stabilization with structural analogues of ATP and of metal fluorides as mimicks of inorganic phosphate. From these results it is possible, in accordance with previous biochemical and molecular biology data, to give a detailed structural description of both ATP hydrolysis and Ca(2+) transport through the membrane, to serve as the starting point for a fuller understanding of the pump mechanism and, in future studies, on the regulatory role of this ubiquitous intracellular Ca(2+)-ATPase in cellular Ca(2+) metabolism in normal and pathological conditions.
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Affiliation(s)
- Jesper Vuust Møller
- Centre for Membrane Pumps in Cells and Disease - PUMPKIN, Danish National Research Foundation, Copenhagen, Denmark.
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29
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Fusca T, Bonza MC, Luoni L, Meneghelli S, Marrano CA, De Michelis MI. Single point mutations in the small cytoplasmic loop of ACA8, a plasma membrane Ca2+-ATPase of Arabidopsis thaliana, generate partially deregulated pumps. J Biol Chem 2009; 284:30881-8. [PMID: 19740735 DOI: 10.1074/jbc.m109.006148] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
ACA8 is a type 2B Ca(2+)-ATPase having a regulatory N terminus whose auto-inhibitory action can be suppressed by binding of calmodulin (CaM) or of acidic phospholipids. ACA8 N terminus is able to interact with a region of the small cytoplasmic loop connecting transmembrane domains 2 and 3. To determine the role of this interaction in auto-inhibition we analyzed single point mutants produced by mutagenesis of ACA8 Glu(252) to Asn(345) sequence. Mutation to Ala of any of six tested acidic residues (Glu(252), Asp(273), Asp(291), Asp(303), Glu(302), or Asp(332)) renders an enzyme that is less dependent on CaM for activity. These results highlight the relevance in ACA8 auto-inhibition of a negative charge of the surface area of the small cytoplasmic loop. The most deregulated of these mutants is D291A ACA8, which is less activated by controlled proteolysis or by acidic phospholipids; the D291A mutant has an apparent affinity for CaM higher than wild-type ACA8. Moreover, its phenotype is stronger than that of D291N ACA8, suggesting a more direct involvement of this residue in the mechanism of auto-inhibition. Among the other produced mutants (I284A, N286A, P289A, P322A, V344A, and N345A), only P322A ACA8 is less dependent on CaM for activity than the wild type. The results reported in this study provide the first evidence that the small cytoplasmic loop of a type 2B Ca(2+)-ATPase plays a role in the attainment of the auto-inhibited state.
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Affiliation(s)
- Tiziana Fusca
- Dipartimento di Biologia L. Gorini, Università di Milano, Istituto di Biofisica del Consiglio Nazionale delle Ricerche, Sezione di Milano, via G. Celoria 26, Milano 20133, Italy
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30
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Vangheluwe P, Sepúlveda MR, Missiaen L, Raeymaekers L, Wuytack F, Vanoevelen J. Intracellular Ca2+- and Mn2+-Transport ATPases. Chem Rev 2009; 109:4733-59. [DOI: 10.1021/cr900013m] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Peter Vangheluwe
- Laboratory of Ca2+-transport ATPases and Laboratory of Molecular and Cellular Signaling, Department of Molecular Cell Biology, Katholieke Universiteit Leuven, Leuven, Belgium
| | - M. Rosario Sepúlveda
- Laboratory of Ca2+-transport ATPases and Laboratory of Molecular and Cellular Signaling, Department of Molecular Cell Biology, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Ludwig Missiaen
- Laboratory of Ca2+-transport ATPases and Laboratory of Molecular and Cellular Signaling, Department of Molecular Cell Biology, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Luc Raeymaekers
- Laboratory of Ca2+-transport ATPases and Laboratory of Molecular and Cellular Signaling, Department of Molecular Cell Biology, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Frank Wuytack
- Laboratory of Ca2+-transport ATPases and Laboratory of Molecular and Cellular Signaling, Department of Molecular Cell Biology, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Jo Vanoevelen
- Laboratory of Ca2+-transport ATPases and Laboratory of Molecular and Cellular Signaling, Department of Molecular Cell Biology, Katholieke Universiteit Leuven, Leuven, Belgium
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31
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Lenoir G, Williamson P, Puts CF, Holthuis JCM. Cdc50p plays a vital role in the ATPase reaction cycle of the putative aminophospholipid transporter Drs2p. J Biol Chem 2009; 284:17956-67. [PMID: 19411703 PMCID: PMC2709398 DOI: 10.1074/jbc.m109.013722] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2009] [Revised: 04/27/2009] [Indexed: 11/06/2022] Open
Abstract
Members of the P(4) subfamily of P-type ATPases are believed to catalyze transport of phospholipids across cellular bilayers. However, most P-type ATPases pump small cations or metal ions, and atomic structures revealed a transport mechanism that is conserved throughout the family. Hence, a challenging problem is to understand how this mechanism is adapted in P(4)-ATPases to flip phospholipids. P(4)-ATPases form heteromeric complexes with Cdc50 proteins. The primary role of these additional polypeptides is unknown. Here, we show that the affinity of yeast P(4)-ATPase Drs2p for its Cdc50-binding partner fluctuates during the transport cycle, with the strongest interaction occurring at a point where the enzyme is loaded with phospholipid ligand. We also find that specific interactions with Cdc50p are required to render the ATPase competent for phosphorylation at the catalytically important aspartate residue. Our data indicate that Cdc50 proteins are integral components of the P(4)-ATPase transport machinery. Thus, acquisition of these subunits may have been a crucial step in the evolution of flippases from a family of cation pumps.
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Affiliation(s)
- Guillaume Lenoir
- From the Department of Membrane Enzymology, Bijvoet Center and Institute of Biomembranes, Utrecht University, 3584 CH Utrecht, The Netherlands and
| | - Patrick Williamson
- the Department of Biology, Amherst College, Amherst, Massachusetts 010022
| | - Catheleyne F. Puts
- From the Department of Membrane Enzymology, Bijvoet Center and Institute of Biomembranes, Utrecht University, 3584 CH Utrecht, The Netherlands and
| | - Joost C. M. Holthuis
- From the Department of Membrane Enzymology, Bijvoet Center and Institute of Biomembranes, Utrecht University, 3584 CH Utrecht, The Netherlands and
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32
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How Ca2+-ATPase pumps ions across the sarcoplasmic reticulum membrane. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2009; 1793:941-6. [DOI: 10.1016/j.bbamcr.2008.10.008] [Citation(s) in RCA: 199] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2008] [Accepted: 10/16/2008] [Indexed: 11/17/2022]
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33
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Holdensen AN, Andersen JP. The length of the A-M3 linker is a crucial determinant of the rate of the Ca2+ transport cycle of sarcoplasmic reticulum Ca2+-ATPase. J Biol Chem 2009; 284:12258-65. [PMID: 19278994 DOI: 10.1074/jbc.m900977200] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ion translocation by the sarcoplasmic reticulum Ca(2+)-ATPase depends on large movements of the A-domain, but the driving forces have yet to be defined. The A-domain is connected to the ion-binding membranous part of the protein through linker regions. We have determined the functional consequences of changing the length of the linker between the A-domain and transmembrane helix M3 ("A-M3 linker") by insertion and deletion mutagenesis at two sites. It was feasible to insert as many as 41 residues (polyglycine and glycine-proline loops) in the flexible region of the linker without loss of the ability to react with Ca(2+) and ATP and to form the phosphorylated Ca(2)E1P intermediate, but the rate of the energy-transducing conformational transition to E2P was reduced by >80%. Insertion of a smaller number of residues gave effects gradually increasing with the length of the insertion. Deletion of two residues at the same site, but not replacement with glycine, gave a similar reduction as the longest insertion. Insertion of one or three residues in another part of the A-M3 linker that forms an alpha-helix ("A3 helix") in E2/E2P conformations had even more profound effects on the ability of the enzyme to form E2P. These results demonstrate the importance of the length of the A-M3 linker and of the position and integrity of the A3 helix for stabilization of E2P and suggest that, during the normal enzyme cycle, strain of the A-M3 linker could contribute to destabilize the Ca(2)E1P state and thereby to drive the transition to E2P.
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Affiliation(s)
- Anne Nyholm Holdensen
- Centre for Membrane Pumps in Cells and Disease-PUMPKIN, Danish National Research Foundation, Department of Physiology and Biophysics, Aarhus University, DK-8000 Aarhus C, Denmark
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34
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Clausen JD, McIntosh DB, Woolley DG, Andersen JP. Critical interaction of actuator domain residues arginine 174, isoleucine 188, and lysine 205 with modulatory nucleotide in sarcoplasmic reticulum Ca2+-ATPase. J Biol Chem 2008; 283:35703-14. [PMID: 18930923 DOI: 10.1074/jbc.m806795200] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
ATP plays dual roles in the reaction cycle of the sarcoplasmic reticulum Ca2+-ATPase by acting as the phosphorylating substrate as well as in nonphosphorylating (modulatory) modes accelerating conformational transitions of the enzyme cycle. Here we have examined the involvement of actuator domain residues Arg174, Ile188, Lys204, and Lys205 by mutagenesis. Alanine mutations to these residues had little effect on the interaction of the Ca2E1 state with nucleotide or on the HnE 2 to Ca2E1 transition of the dephosphoenzyme. The phosphoenzyme processing steps, Ca2E1P to E2P and E2P dephosphorylation, and their stimulation by MgATP/ATP were markedly affected by mutations to Arg174, Ile188, and Lys205. Replacement of Ile188 with alanine abolished nucleotide modulation of dephosphorylation but not the modulation of the Ca2E1P to E2P transition. Mutation to Arg174 interfered with nucleotide modulation of either of the phosphoenzyme processing steps, indicating a significant overlap between the modulatory nucleotide-binding sites involved. Mutation to Lys205 enhanced the rates of the phosphoenzyme processing steps in the absence of nucleotide and disrupted the nucleotide modulation of the Ca2E1P to E2P transition. Remarkably, the mutants with alterations to Lys205 showed an anomalous inhibition by ATP of the dephosphorylation, and in the alanine mutant the affinity for the inhibition by ATP was indistinguishable from that for stimulation by ATP of the wild type. Hence, the actuator domain is an important player in the function of ATP as modulator of phosphoenzyme processing, with Arg174, Ile188, and Lys205 all being critically involved, although in different ways. The data support a variable site model for the modulatory effects with the nucleotide binding somewhat differently in each of the conformational states occurring during the transport cycle.
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Affiliation(s)
- Johannes D Clausen
- Department of Physiology and Biophysics, Aarhus University, DK-8000 Aarhus C, Denmark
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35
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Faller LD. Mechanistic studies of sodium pump. Arch Biochem Biophys 2008; 476:12-21. [PMID: 18558080 DOI: 10.1016/j.abb.2008.05.017] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2008] [Revised: 05/22/2008] [Accepted: 05/23/2008] [Indexed: 11/27/2022]
Abstract
Sodium pump was the first ion pump discovered. A member of the family of active transporters that catalyze adenosine 5'-triphosphate hydrolysis by forming a phosphorylated enzyme intermediate, sodium pump couples the energy released to unequal countertransport of sodium and potassium ions. The ion gradient generated by the pump is important for a variety of secondary physiological processes ranging from metabolite transport to electrical excitation of nerve and muscle. Selected experiments relating structure to function are reviewed.
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Affiliation(s)
- Larry D Faller
- University of California at Los Angeles and Veterans Administration Greater Los Angeles Health Care System, Los Angeles, CA 90073, USA.
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36
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Structural aspects of ion pumping by Ca2+-ATPase of sarcoplasmic reticulum. Arch Biochem Biophys 2008; 476:3-11. [PMID: 18455499 DOI: 10.1016/j.abb.2008.04.017] [Citation(s) in RCA: 159] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2008] [Accepted: 04/09/2008] [Indexed: 11/22/2022]
Abstract
Ca2+-ATPase of muscle sarcoplasmic reticulum is an ATP-powered Ca2+-pump that establishes a >10,000-fold concentration gradient across the membrane. Its crystal structures have been determined for nine different states that cover nearly the entire reaction cycle. Presented here is a brief structural account of the ion pumping process, which is achieved by a series of very large domain rearrangements.
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37
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Roles of transmembrane segment M1 of Na+,K+-ATPase and Ca2-ATPase, the gatekeeper and the pivot. J Bioenerg Biomembr 2008; 39:357-66. [PMID: 18058007 DOI: 10.1007/s10863-007-9106-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
In this review we summarize mutagenesis work on the structure-function relationship of transmembrane segment M1 in the Na+,K+-ATPase and the sarco(endo)plasmic reticulum Ca2+-ATPase. The original hypothesis that charged residues in the N-terminal part of M1 interact with the transported cations can be rejected. On the other hand hydrophobic residues in the middle part of M1 turned out to play crucial roles in Ca2+ interaction/occlusion in Ca2+-ATPase and K+ interaction/occlusion in Na+,K+-ATPase. Leu65 of the Ca2+-ATPase and Leu99 of the Na+,K+-ATPase, located at homologous positions in M1, function as gate-locking residues that restrict the mobility of the side chain of the cation binding/gating residue of transmembrane segment M4, Glu309/Glu329. A pivot formed between a pair of a glycine and a bulky residue in M1 and M3 seems critical to the opening of the extracytoplasmic gate in both the Ca2+-ATPase and the Na+,K+-ATPase.
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38
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Marchand A, Winther AML, Holm PJ, Olesen C, Montigny C, Arnou B, Champeil P, Clausen JD, Vilsen B, Andersen JP, Nissen P, Jaxel C, Møller JV, le Maire M. Crystal structure of D351A and P312A mutant forms of the mammalian sarcoplasmic reticulum Ca(2+) -ATPase reveals key events in phosphorylation and Ca(2+) release. J Biol Chem 2008; 283:14867-82. [PMID: 18356161 DOI: 10.1074/jbc.m710165200] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In recent years crystal structures of the sarcoplasmic reticulum Ca(2+)-ATPase (SERCA1a), stabilized in various conformations with nucleotide and phosphate analogs, have been obtained. However, structural analysis of mutant forms would also be valuable to address key mechanistic aspects. We have worked out a procedure for affinity purification of SERCA1a heterologously expressed in yeast cells, producing sufficient amounts for crystallization and biophysical studies. We present here the crystal structures of two mutant forms, D351A and P312A, to address the issue whether the profound functional changes seen for these mutants are caused by major structural changes. We find that the structure of P312A with ADP and AlF(4)(-) bound (3.5-A resolution) and D351A with AMPPCP or ATP bound (3.4- and 3.7-A resolution, respectively) deviate only slightly from the complexes formed with that of wild-type ATPase. ATP affinity of the D351A mutant was very high, whereas the affinity for cytosolic Ca(2+) was similar to that of the wild type. We conclude from an analysis of data that the extraordinary affinity of the D351A mutant for ATP is caused by the electrostatic effects of charge removal and not by a conformational change. P312A exhibits a profound slowing of the Ca(2+)-translocating Ca(2)E1P-->E2P transition, which seems to be due to a stabilization of Ca(2)E1P rather than a destabilization of E2P. This can be accounted for by the strain that the Pro residue induces in the straight M4 helix of the wild type, which is removed upon the replacement of Pro(312) with alanine in P312A.
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Affiliation(s)
- Alexandre Marchand
- Commissariat à l'Energie Atomique (CEA), Institut de Biologie et de Technologies de Saclay, SBSM, URA CNRS 2096, Laboratoire de Recherche Associé, 17V University of Paris-Sud, Gif sur Yvette, France
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39
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How processing of aspartylphosphate is coupled to lumenal gating of the ion pathway in the calcium pump. Proc Natl Acad Sci U S A 2007; 104:19831-6. [PMID: 18077416 DOI: 10.1073/pnas.0709978104] [Citation(s) in RCA: 128] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ca(2+)-ATPase of skeletal muscle sarcoplasmic reticulum is the best-studied member of the P-type or E1/E2 type ion transporting ATPases. It has been crystallized in seven different states that cover nearly the entire reaction cycle. Here we describe the structure of this ATPase complexed with phosphate analogs BeF(3)(-) and AlF(4)(-) in the absence of Ca(2+), which correspond to the E2P ground state and E2 approximately P transition state, respectively. The luminal gate is open with BeF(3)(-) and closed with AlF(4)(-). These and the E1 approximately P.ADP analog crystal structures show that a two-step rotation of the cytoplasmic A-domain opens and closes the luminal gate through the movements of the M1-M4 transmembrane helices. There are several conformational switches coupled to the rotation, and the one in the cytoplasmic part of M2 has critical importance. In the second step of rotation, positioning of one water molecule couples the hydrolysis of aspartylphosphate to closing of the gate.
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40
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On the origin of lipid asymmetry: the flip side of ion transport. Curr Opin Chem Biol 2007; 11:654-61. [DOI: 10.1016/j.cbpa.2007.09.008] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2007] [Revised: 09/11/2007] [Accepted: 09/20/2007] [Indexed: 11/19/2022]
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41
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Daiho T, Yamasaki K, Danko S, Suzuki H. Critical role of Glu40-Ser48 loop linking actuator domain and first transmembrane helix of Ca2+-ATPase in Ca2+ deocclusion and release from ADP-insensitive phosphoenzyme. J Biol Chem 2007; 282:34429-47. [PMID: 17881350 DOI: 10.1074/jbc.m707665200] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The functional importance of the length of the A/M1 linker (Glu(40)-Ser(48)) connecting the actuator domain and the first transmembrane helix of sarcoplasmic reticulum Ca(2+)-ATPase was explored by its elongation with glycine insertion at Pro(42)/Ala(43) and Gly(46)/Lys(47). Two or more glycine insertions at each site completely abolished ATPase activity. The isomerization of phosphoenzyme (EP) intermediate from the ADP-sensitive form (E1P) to the ADP-insensitive form (E2P) was markedly accelerated, but the decay of EP was completely blocked in these mutants. The E2P accumulated was therefore demonstrated to be E2PCa(2) possessing two occluded Ca(2+) ions at the transport sites, and the Ca(2+) deocclusion and release into lumen were blocked in the mutants. By contrast, the hydrolysis of the Ca(2+)-free form of E2P produced from P(i) without Ca(2+) was as rapid in the mutants as in the wild type. Analysis of resistance against trypsin and proteinase K revealed that the structure of E2PCa(2) accumulated is an intermediate state between E1PCa(2) and the Ca(2+)-released E2P state. Namely in E2PCa(2), the actuator domain is already largely rotated from its position in E1PCa(2) and associated with the phosphorylation domain as in the Ca(2+)-released E2P state; however, in E2PCa(2), the hydrophobic interactions among these domains and Leu(119)/Tyr(122) on the top of second transmembrane helix are not yet formed properly. This is consistent with our previous finding that these interactions at Tyr(122) are critical for formation of the Ca(2+)-released E2P structure. Results showed that the EP isomerization/Ca(2+)-release process consists of the following two steps: E1PCa(2) --> E2PCa(2) --> E2P + 2Ca(2+); and the intermediate state E2PCa(2) was identified for the first time. Results further indicated that the A/M1 linker with its appropriately short length, probably because of the strain imposed in E2PCa(2), is critical for the correct positioning and interactions of the actuator and phosphorylation domains to cause structural changes for the Ca(2+) deocclusion and release.
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Affiliation(s)
- Takashi Daiho
- Department of Biochemistry, Asahikawa Medical College, Midorigaoka-higashi, Asahikawa, Japan.
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42
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Lutsenko S, Barnes NL, Bartee MY, Dmitriev OY. Function and regulation of human copper-transporting ATPases. Physiol Rev 2007; 87:1011-46. [PMID: 17615395 DOI: 10.1152/physrev.00004.2006] [Citation(s) in RCA: 554] [Impact Index Per Article: 32.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Copper-transporting ATPases (Cu-ATPases) ATP7A and ATP7B are evolutionarily conserved polytopic membrane proteins with essential roles in human physiology. The Cu-ATPases are expressed in most tissues, and their transport activity is crucial for central nervous system development, liver function, connective tissue formation, and many other physiological processes. The loss of ATP7A or ATP7B function is associated with severe metabolic disorders, Menkes disease, and Wilson disease. In cells, the Cu-ATPases maintain intracellular copper concentration by transporting copper from the cytosol across cellular membranes. They also contribute to protein biosynthesis by delivering copper into the lumen of the secretory pathway where metal ion is incorporated into copper-dependent enzymes. The biosynthetic and homeostatic functions of Cu-ATPases are performed in different cell compartments; targeting to these compartments and the functional activity of Cu-ATPase are both regulated by copper. In recent years, significant progress has been made in understanding the structure, function, and regulation of these essential transporters. These studies raised many new questions related to specific physiological roles of Cu-ATPases in various tissues and complex mechanisms that control the Cu-ATPase function. This review summarizes current data on the structural organization and functional properties of ATP7A and ATP7B as well as their localization and functions in various tissues, and discusses the current models of regulated trafficking of human Cu-ATPases.
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Affiliation(s)
- Svetlana Lutsenko
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, Oregon 97239, USA.
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43
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Carreira ACO, Bastos CMV, Verjovski-Almeida S. Probing the SERCA1a sarcoplasmic reticulum Ca2+-ATPase phosphorylation-site mutant D351E with inorganic phosphate. ACTA ACUST UNITED AC 2007; 40:1323-32. [PMID: 17713651 DOI: 10.1590/s0100-879x2006005000160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2007] [Accepted: 06/25/2007] [Indexed: 11/21/2022]
Abstract
The expression of sarcoplasmic reticulum SERCA1a Ca2+-ATPase wild-type and D351E mutants was optimized in yeast under the control of a galactose promoter. Fully active wild-type enzyme was recovered in yeast microsomal membrane fractions in sufficient amounts to permit a rapid and practical assay of ATP hydrolysis and phosphoenzyme formation from ATP or Pi. Mutant and wild-type Ca2+-ATPase were assayed for phosphorylation by Pi under conditions that are known to facilitate this reaction in the wild-type enzyme, including pH 6.0 or 7.0 at 25 degrees C in the presence of dimethylsulfoxide. Although glutamyl (E) and aspartyl (D) residue side chains differ by only one methylene group, no phosphoenzyme could be detected in the D351E mutant, even upon the addition of 40% dimethylsulfoxide and 1 mM 32Pi in the presence of 10 mM EGTA and 5 mM MgCl2. These results show that in the D351E mutant, increasing hydrophobicity of the site with inorganic solvent was not a sufficient factor for the required abstraction of water in the reaction of E351 with Pi to form a glutamylphosphate (P-E351) phosphoenzyme moiety. Mutation D351E may disrupt the proposed alignment of the reactive water molecule with the aspartylphosphate (P-D351) moiety in the phosphorylation site, which may be an essential alignment both in the forward reaction (hydrolysis of aspartylphosphate) and in the reverse reaction (abstraction of water upon formation of an aspartylphosphate intermediate).
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Affiliation(s)
- A C O Carreira
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, SP, Brasil
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44
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Clausen JD, McIntosh DB, Anthonisen AN, Woolley DG, Vilsen B, Andersen JP. ATP-binding modes and functionally important interdomain bonds of sarcoplasmic reticulum Ca2+-ATPase revealed by mutation of glycine 438, glutamate 439, and arginine 678. J Biol Chem 2007; 282:20686-97. [PMID: 17504757 DOI: 10.1074/jbc.m702365200] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
ATP binds to sarcoplasmic reticulum Ca(2+)-ATPase both in a phosphorylating (catalytic) mode and in a nonphosphorylating (modulatory) mode, the latter leading to acceleration of phosphoenzyme turnover (Ca(2)E(1)P --> E(2)P and E(2)P --> E(2) reactions) and Ca(2+) binding (E(2) --> Ca(2)E(1)). In some of the Ca(2+)-ATPase crystal structures, Arg(678) and Glu(439) seem to be involved in the binding of nucleotide or an associated Mg(2+) ion. We have replaced Arg(678), Glu(439), and Gly(438) with alanine to examine their importance for the enzyme cycle and the modulatory effects of ATP and MgATP. The results point to the key role of Arg(678) in nucleotide binding and to the importance of interdomain bonds Glu(439)-Ser(186) and Arg(678)-Asp(203) in stabilizing the E(2)P and E(2) intermediates, respectively. Mutation of Arg(678) had conspicuous effects on ATP/MgATP binding to the E(1) form and ADP binding to Ca(2)E(1)P, as well as ATP/MgATP binding in modulatory modes to E(2)P and E(2), whereas the effects on ATP/MgATP acceleration of the Ca(2)E(1)P --> E(2)P transition were small, suggesting that the nucleotide that accelerates Ca(2)E(1)P --> E(2)P binds differently from that modulating the E(2)P --> E(2) and E(2) --> Ca(2)E(1) reactions. Mutation of Glu(439) hardly affected nucleotide binding to E(1), Ca(2)E(1)P, and E(2), but it led to disruption of the modulatory effect of ATP on E(2)P --> E(2) and acceleration of the latter reaction, indicating that ATP normally modulates E(2)P --> E(2) by interfering with the interaction between Glu(439) and Ser(186). Gly(438) seems to be important for this interaction as well as for nucleotide binding, probably because of its role in formation of the helix containing Glu(439) and Thr(441).
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Affiliation(s)
- Johannes D Clausen
- Department of Physiology, Institute of Physiology and Biophysics, University of Aarhus, Ole Worms Allé 1160, DK-8000 Aarhus C, Denmark
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Toyoshima C. Ion pumping by calcium ATPase of sarcoplasmic reticulum. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2007; 592:295-303. [PMID: 17278374 DOI: 10.1007/978-4-431-38453-3_25] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Affiliation(s)
- Chikashi Toyoshima
- Institute of Molecular and Cellular Biosciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
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46
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Buch-Pedersen MJ, Rudashevskaya EL, Berner TS, Venema K, Palmgren MG. Potassium as an intrinsic uncoupler of the plasma membrane H+-ATPase. J Biol Chem 2006; 281:38285-92. [PMID: 17056603 DOI: 10.1074/jbc.m604781200] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The plant plasma membrane proton pump (H(+)-ATPase) is stimulated by potassium, but it has remained unclear whether potassium is actually transported by the pump or whether it serves other roles. We now show that K(+) is bound to the proton pump at a site involving Asp(617) in the cytoplasmic phosphorylation domain, from where it is unlikely to be transported. Binding of K(+) to this site can induce dephosphorylation of the phosphorylated E(1)P reaction cycle intermediate by a mechanism involving Glu(184) in the conserved TGES motif of the pump actuator domain. Our data identify K(+) as an intrinsic uncoupler of the proton pump and suggest a mechanism for control of the H(+)/ATP coupling ratio. K(+)-induced dephosphorylation of E(1)P may serve regulatory purposes and play a role in negative regulation of the transmembrane electrochemical gradient under cellular conditions where E(1)P is accumulating.
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Affiliation(s)
- Morten J Buch-Pedersen
- Department of Plant Biology, The Royal Veterinary and Agricultural University, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Copenhagen, Denmark.
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47
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Anthonisen AN, Clausen JD, Andersen JP. Mutational Analysis of the Conserved TGES Loop of Sarcoplasmic Reticulum Ca2+-ATPase. J Biol Chem 2006. [DOI: 10.1016/s0021-9258(19)84071-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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48
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Baekgaard L, Fuglsang AT, Palmgren MG. Regulation of plant plasma membrane H+- and Ca2+-ATPases by terminal domains. J Bioenerg Biomembr 2006; 37:369-74. [PMID: 16691467 DOI: 10.1007/s10863-005-9473-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
In the last few years, major progress has been made to elucidate the structure, function, and regulation of P-type plasma membrane H(+)-and Ca(2+)-ATPases. Even though a number of regulatory proteins have been identified, many pieces are still lacking in order to understand the complete regulatory mechanisms of these pumps. In plant plasma membrane H(+)- and Ca(2+)-ATPases, autoinhibitory domains are situated in the C- and N-terminal domains, respectively. A model for a common mechanism of autoinhibition is discussed.
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Affiliation(s)
- Lone Baekgaard
- Department of Plant Biology, The Royal Veterinary and Agricultural University, Frederiksberg C, Denmark.
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49
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Møller JV, Olesen C, Jensen AML, Nissen P. The structural basis for coupling of Ca2+ transport to ATP hydrolysis by the sarcoplasmic reticulum Ca2+-ATPase. J Bioenerg Biomembr 2006; 37:359-64. [PMID: 16691465 DOI: 10.1007/s10863-005-9471-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Recently, a series of structure determinations has nearly completed a structural description of the transport cycle of the sarcoplasmic reticulum Ca(2+)-ATPase, especially those steps concerned with the phosphorylation by ATP and the dephosphorylation reaction. From these structures Ca(2+)-ATPase emerges as a molecular machine, where globular cytosolic domains and transmembrane helices work in concert like a mechanical pump, as can be vividly demonstrated in animated versions of the pump cycle. The structures show that both ATP phosphorylation and dephosphorylation at Asp351 take place as nucleophilic SN2 reactions, which are associated with Ca(2+) and H(+) occluded states, respectively. These transitory steps ensure efficient coupling between Ca(2+) transport and ATP hydrolysis.
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Affiliation(s)
- Jesper Vuust Møller
- Department of Biophysics, Institute of Physiology and Biophysics, University of Aarhus, DK-8000, Aarhus C, Denmark.
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50
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Anthonisen AN, Clausen JD, Andersen JP. Mutational Analysis of the Conserved TGES Loop of Sarcoplasmic Reticulum Ca2+-ATPase. J Biol Chem 2006; 281:31572-82. [PMID: 16893884 DOI: 10.1074/jbc.m605194200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Crystal structures have shown that the conserved TGES loop of the Ca2+-ATPase is isolated in the Ca2E1 state but becomes inserted in the catalytic site in E2 states. Here, we have examined the kinetics of the partial reaction steps of the transport cycle and the binding of the phosphoryl analogs BeF, AlF, MgF, and vanadate in mutants with alterations to the TGES residues. The mutations encompassed variation of size, polarity, and charge of the side chains. Differential effects on the Ca2E1P --> E2P, E2P --> E2, and E2 --> Ca2E1 reactions and the binding of the phosphoryl analogs were observed. In the E183D mutant, the E2P --> E2 dephosphorylation reaction proceeded at a rate as high as one-third that of the wild type, whereas it was very slow in the other Glu183 mutants, including E183Q, thus demonstrating the need for a negatively charged carboxylate group to catalyze dephosphorylation. By contrast, the Ca2E1P --> E2P transition was accomplished at a reasonable rate with glutamine in place of Glu183, but not with aspartate, indicating that the length of the Glu183 side chain, in addition to its hydrogen bonding potential, is critical for Ca2E1P --> E2P. This transition was also slowed in mutants with alteration to other TGES residues. The data provide functional evidence in support of the proposed role of Glu183 in activating the water molecule involved in the E2P --> E2 dephosphorylation and suggest a direct participation of the side chains of the TGES loop in the control and facilitation of the insertion of the loop in the catalytic site. The interactions of the TGES loop furthermore seem to facilitate its disengagement from the catalytic site during the E2 --> Ca2E1 transition.
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Affiliation(s)
- Anne Nyholm Anthonisen
- Department of Physiology, Institute of Physiology and Biophysics, University of Aarhus, DK-8000 Aarhus C, Denmark
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