1
|
Reithmeier RAF, Casey JR, Kalli AC, Sansom MSP, Alguel Y, Iwata S. Band 3, the human red cell chloride/bicarbonate anion exchanger (AE1, SLC4A1), in a structural context. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:1507-32. [PMID: 27058983 DOI: 10.1016/j.bbamem.2016.03.030] [Citation(s) in RCA: 127] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Revised: 03/21/2016] [Accepted: 03/29/2016] [Indexed: 02/03/2023]
Abstract
The crystal structure of the dimeric membrane domain of human Band 3(1), the red cell chloride/bicarbonate anion exchanger 1 (AE1, SLC4A1), provides a structural context for over four decades of studies into this historic and important membrane glycoprotein. In this review, we highlight the key structural features responsible for anion binding and translocation and have integrated the following topological markers within the Band 3 structure: blood group antigens, N-glycosylation site, protease cleavage sites, inhibitor and chemical labeling sites, and the results of scanning cysteine and N-glycosylation mutagenesis. Locations of mutations linked to human disease, including those responsible for Southeast Asian ovalocytosis, hereditary stomatocytosis, hereditary spherocytosis, and distal renal tubular acidosis, provide molecular insights into their effect on Band 3 folding. Finally, molecular dynamics simulations of phosphatidylcholine self-assembled around Band 3 provide a view of this membrane protein within a lipid bilayer.
Collapse
Affiliation(s)
- Reinhart A F Reithmeier
- Department of Biochemistry, 1 King's College Circle, University of Toronto, Toronto M5S 1A8, Canada.
| | - Joseph R Casey
- Department of Biochemistry, Membrane Protein Disease Research Group, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
| | - Antreas C Kalli
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Mark S P Sansom
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Yilmaz Alguel
- Division of Molecular Biosciences, Imperial College London, London, SW7 2AZ, UK
| | - So Iwata
- Division of Molecular Biosciences, Imperial College London, London, SW7 2AZ, UK
| |
Collapse
|
2
|
Ling S, Zhang C, Wang W, Cai X, Yu L, Wu F, Zhang L, Tian C. Combined approaches of EPR and NMR illustrate only one transmembrane helix in the human IFITM3. Sci Rep 2016; 6:24029. [PMID: 27046158 PMCID: PMC4820770 DOI: 10.1038/srep24029] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Accepted: 03/18/2016] [Indexed: 11/09/2022] Open
Abstract
Interferon-inducible transmembrane protein IFITM3 was known to restrict the entry of a wide spectrum of viruses to the cytosol of the host. The mechanism used by the protein to restrict viral entry is unclear given the unavailability of the membrane topology and structures of the IFITM family proteins. Systematic site-directed spin labeling (SDSL) and electron paramagnetic resonance (EPR) studies of IFITM3 in detergent micelles identified a single, long transmembrane helix in the C-terminus and an intramembrane segment in the N-terminal hydrophobic region. Solution NMR studies of the same sample verified the secondary structure distribution and demonstrated two rigid regions interacting with the micellar surface. The resulting membrane topology of IFITM3 supports the mechanism of an enhanced restricted membrane hemi-fusion.
Collapse
Affiliation(s)
- Shenglong Ling
- Hefei National Laboratory of Microscale Physical Sciences, School of Life Science, University of Science and Technology of China, Hefei, 230027, P. R. China
| | - Chengwei Zhang
- Hefei National Laboratory of Microscale Physical Sciences, School of Life Science, University of Science and Technology of China, Hefei, 230027, P. R. China
| | - Wei Wang
- Hefei National Laboratory of Microscale Physical Sciences, School of Life Science, University of Science and Technology of China, Hefei, 230027, P. R. China
| | - Xiaoying Cai
- Hefei National Laboratory of Microscale Physical Sciences, School of Life Science, University of Science and Technology of China, Hefei, 230027, P. R. China
| | - Lu Yu
- High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, 230031, P. R. China
| | - Fangming Wu
- High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, 230031, P. R. China
| | - Longhua Zhang
- Hefei National Laboratory of Microscale Physical Sciences, School of Life Science, University of Science and Technology of China, Hefei, 230027, P. R. China
| | - Changlin Tian
- Hefei National Laboratory of Microscale Physical Sciences, School of Life Science, University of Science and Technology of China, Hefei, 230027, P. R. China.,High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, 230031, P. R. China
| |
Collapse
|
3
|
Structure of an E. coli integral membrane sulfurtransferase and its structural transition upon SCN(-) binding defined by EPR-based hybrid method. Sci Rep 2016; 6:20025. [PMID: 26817826 PMCID: PMC4730233 DOI: 10.1038/srep20025] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Accepted: 12/14/2015] [Indexed: 12/02/2022] Open
Abstract
Electron paramagnetic resonance (EPR)-based hybrid experimental and computational approaches were applied to determine the structure of a full-length E. coli integral membrane sulfurtransferase, dimeric YgaP, and its structural and dynamic changes upon ligand binding. The solution NMR structures of the YgaP transmembrane domain (TMD) and cytosolic catalytic rhodanese domain were reported recently, but the tertiary fold of full-length YgaP was not yet available. Here, systematic site-specific EPR analysis defined a helix-loop-helix secondary structure of the YagP-TMD monomers using mobility, accessibility and membrane immersion measurements. The tertiary folds of dimeric YgaP-TMD and full-length YgaP in detergent micelles were determined through inter- and intra-monomer distance mapping and rigid-body computation. Further EPR analysis demonstrated the tight packing of the two YgaP second transmembrane helices upon binding of the catalytic product SCN−, which provides insight into the thiocyanate exportation mechanism of YgaP in the E. coli membrane.
Collapse
|
4
|
Stein RA, Beth AH, Hustedt EJ. A Straightforward Approach to the Analysis of Double Electron-Electron Resonance Data. Methods Enzymol 2015; 563:531-67. [PMID: 26478498 PMCID: PMC5231402 DOI: 10.1016/bs.mie.2015.07.031] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Double electron-electron resonance (DEER) is now widely utilized to measure distance distributions in the 20-70Å range. DEER is frequently applied to biological systems that have multiple conformational states leading to complex distance distributions. These complex distributions raise issues regarding the best approach to analyze DEER data. A widely used method utilizes a priori background correction followed by Tikhonov regularization. Unfortunately, the underlying assumptions of this approach can impact the analysis. In this chapter, a method of analyzing DEER data is presented that is ideally suited to obtain these complex distance distributions. The approach allows the fitting of raw experimental data without a priori background correction as well as the rigorous determination of uncertainties for all fitting parameters. This same methodological approach can be used for the simultaneous or global analysis of multiple DEER data sets using variable ratios of a common set of components, thus allowing direct correlation of distance components with functionally relevant conformational and biochemical states. Examples are given throughout to highlight this robust fitting approach.
Collapse
Affiliation(s)
- Richard A Stein
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, USA
| | - Albert H Beth
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, USA
| | - Eric J Hustedt
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, USA.
| |
Collapse
|
5
|
Cordat E, Reithmeier RA. Structure, Function, and Trafficking of SLC4 and SLC26 Anion Transporters. CURRENT TOPICS IN MEMBRANES 2014; 73:1-67. [DOI: 10.1016/b978-0-12-800223-0.00001-3] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
|
6
|
Dixit M, Kim S, Matthews GF, Erreger K, Galli A, Cobb CE, Hustedt EJ, Beth AH. Structural arrangement of the intracellular Ca2+ binding domains of the cardiac Na+/Ca2+ exchanger (NCX1.1): effects of Ca2+ binding. J Biol Chem 2012; 288:4194-207. [PMID: 23233681 DOI: 10.1074/jbc.m112.423293] [Citation(s) in RCA: 8] [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 cardiac Na(+)/Ca(2+) exchanger (NCX1.1) serves as the primary means of Ca(2+) extrusion across the plasma membrane of cardiomyocytes after the rise in intracellular Ca(2+) during contraction. The exchanger is regulated by binding of Ca(2+) to its intracellular domain, which contains two structurally homologous Ca(2+) binding domains denoted as CBD1 and CBD2. NMR and x-ray crystallographic studies have provided structures for the isolated CBD1 and CBD2 domains and have shown how Ca(2+) binding affects their structures and motional dynamics. However, structural information on the entire Ca(2+) binding domain, denoted CBD12, and how binding of Ca(2+) alters its structure and dynamics is more limited. Site-directed spin labeling has been employed in this work to address these questions. Electron paramagnetic resonance measurements on singly labeled constructs of CBD12 have identified the regions that undergo changes in dynamics as a result of Ca(2+) binding. Double electron-electron resonance (DEER) measurements on doubly labeled constructs of CBD12 have shown that the β-sandwich regions of the CBD1 and CBD2 domains are largely insensitive to Ca(2+) binding and that these two domains are widely separated at their N and C termini. Interdomain distances measured by DEER have been employed to construct structural models for CBD12 in the presence and absence of Ca(2+). These models show that there is not a major change in the relative orientation of the two Ca(2+) binding domains as a result of Ca(2+) binding in the NCX1.1 isoform. Additional measurements have shown that there are significant changes in the dynamics of the F-G loop region of CBD2 that merit further characterization with regard to their possible involvement in regulation of NCX1.1 activity.
Collapse
Affiliation(s)
- Mrinalini Dixit
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee 37232, USA
| | | | | | | | | | | | | | | |
Collapse
|
7
|
Brandon S, Beth AH, Hustedt EJ. The global analysis of DEER data. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2012; 218:93-104. [PMID: 22578560 PMCID: PMC3608411 DOI: 10.1016/j.jmr.2012.03.006] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2011] [Revised: 03/10/2012] [Accepted: 03/12/2012] [Indexed: 05/11/2023]
Abstract
Double Electron-Electron Resonance (DEER) has emerged as a powerful technique for measuring long range distances and distance distributions between paramagnetic centers in biomolecules. This information can then be used to characterize functionally relevant structural and dynamic properties of biological molecules and their macromolecular assemblies. Approaches have been developed for analyzing experimental data from standard four-pulse DEER experiments to extract distance distributions. However, these methods typically use an a priori baseline correction to account for background signals. In the current work an approach is described for direct fitting of the DEER signal using a model for the distance distribution which permits a rigorous error analysis of the fitting parameters. Moreover, this approach does not require a priori background correction of the experimental data and can take into account excluded volume effects on the background signal when necessary. The global analysis of multiple DEER data sets is also demonstrated. Global analysis has the potential to provide new capabilities for extracting distance distributions and additional structural parameters in a wide range of studies.
Collapse
Affiliation(s)
| | | | - Eric J. Hustedt
- Corresponding author. Address: 735B Light Hall, Vanderbilt University, Nashville, TN 37232, United States. (E.J. Hustedt)
| |
Collapse
|
8
|
Benson MA, Komas SM, Schmalzer KM, Casey MS, Frank DW, Feix JB. Induced conformational changes in the activation of the Pseudomonas aeruginosa type III toxin, ExoU. Biophys J 2011; 100:1335-43. [PMID: 21354407 DOI: 10.1016/j.bpj.2011.01.056] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2010] [Revised: 01/07/2011] [Accepted: 01/25/2011] [Indexed: 02/07/2023] Open
Abstract
ExoU is a 74-kDa, water-soluble toxin injected directly into mammalian cells through the type III secretion system of the opportunistic pathogen, Pseudomonas aeruginosa. Previous studies have shown that ExoU is a Ca(2+)-independent phospholipase that requires a eukaryotic protein cofactor. One protein capable of activating ExoU and serving as a required cofactor was identified by biochemical and proteomic methods as superoxide dismutase (SOD1). In these studies, we carried out site-directed spin-labeling electron paramagnetic resonance spectroscopy to examine the effects of SOD1 and substrate liposomes on the structure and dynamics of ExoU. Local conformational changes within the catalytic site were observed in the presence of substrate liposomes, and were enhanced by the addition of SOD1 in a concentration-dependent manner. Conformational changes in the C-terminal domain of ExoU were observed upon addition of cofactor, even in the absence of liposomes. Double electron-electron resonance experiments indicated that ExoU samples multiple conformations in the resting state. In contrast, addition of SOD1 induced ExoU to adopt a single, well-defined conformation. These studies provide, to our knowledge, the first direct evidence for cofactor- and membrane-induced conformational changes in the mechanism of activation of ExoU.
Collapse
Affiliation(s)
- Marc A Benson
- Center for Infectious Disease Research, Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | | | | | | | | | | |
Collapse
|
9
|
Kim S, Brandon S, Zhou Z, Cobb CE, Edwards SJ, Moth CW, Parry CS, Smith JA, Lybrand TP, Hustedt EJ, Beth AH. Determination of structural models of the complex between the cytoplasmic domain of erythrocyte band 3 and ankyrin-R repeats 13-24. J Biol Chem 2011; 286:20746-57. [PMID: 21493712 DOI: 10.1074/jbc.m111.230326] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The adaptor protein ankyrin-R interacts via its membrane binding domain with the cytoplasmic domain of the anion exchange protein (AE1) and via its spectrin binding domain with the spectrin-based membrane skeleton in human erythrocytes. This set of interactions provides a bridge between the lipid bilayer and the membrane skeleton, thereby stabilizing the membrane. Crystal structures for the dimeric cytoplasmic domain of AE1 (cdb3) and for a 12-ankyrin repeat segment (repeats 13-24) from the membrane binding domain of ankyrin-R (AnkD34) have been reported. However, structural data on how these proteins assemble to form a stable complex have not been reported. In the current studies, site-directed spin labeling, in combination with electron paramagnetic resonance (EPR) and double electron-electron resonance, has been utilized to map the binding interfaces of the two proteins in the complex and to obtain inter-protein distance constraints. These data have been utilized to construct a family of structural models that are consistent with the full range of experimental data. These models indicate that an extensive area on the peripheral domain of cdb3 binds to ankyrin repeats 18-20 on the top loop surface of AnkD34 primarily through hydrophobic interactions. This is a previously uncharacterized surface for binding of cdb3 to AnkD34. Because a second dimer of cdb3 is known to bind to ankyrin repeats 7-12 of the membrane binding domain of ankyrin-R, the current models have significant implications regarding the structural nature of a tetrameric form of AE1 that is hypothesized to be involved in binding to full-length ankyrin-R in the erythrocyte membrane.
Collapse
Affiliation(s)
- Sunghoon Kim
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee 37232-0615, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
10
|
Bowman A, Ward R, El-Mkami H, Owen-Hughes T, Norman DG. Probing the (H3-H4)2 histone tetramer structure using pulsed EPR spectroscopy combined with site-directed spin labelling. Nucleic Acids Res 2010; 38:695-707. [PMID: 19914933 PMCID: PMC2810997 DOI: 10.1093/nar/gkp1003] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2009] [Revised: 10/06/2009] [Accepted: 10/12/2009] [Indexed: 12/30/2022] Open
Abstract
The (H3-H4)(2) histone tetramer forms the central core of nucleosomes and, as such, plays a prominent role in assembly, disassembly and positioning of nucleosomes. Despite its fundamental role in chromatin, the tetramer has received little structural investigation. Here, through the use of pulsed electron-electron double resonance spectroscopy coupled with site-directed spin labelling, we survey the structure of the tetramer in solution. We find that tetramer is structurally more heterogeneous on its own than when sequestered in the octamer or nucleosome. In particular, while the central region including the H3-H3' interface retains a structure similar to that observed in nucleosomes, other regions such as the H3 alphaN helix display increased structural heterogeneity. Flexibility of the H3 alphaN helix in the free tetramer also illustrates the potential for post-translational modifications to alter the structure of this region and mediate interactions with histone chaperones. The approach described here promises to prove a powerful system for investigating the structure of additional assemblies of histones with other important factors in chromatin assembly/fluidity.
Collapse
Affiliation(s)
- Andrew Bowman
- Wellcome Trust Centre for Gene Regulation and Expression, Nucleic Acid Structure Research Group, College of Life Sciences, University of Dundee, Dundee DD1 5EH and School of Physics and Astronomy, University of St Andrews, St Andrews FE2 4KM, UK
| | - Richard Ward
- Wellcome Trust Centre for Gene Regulation and Expression, Nucleic Acid Structure Research Group, College of Life Sciences, University of Dundee, Dundee DD1 5EH and School of Physics and Astronomy, University of St Andrews, St Andrews FE2 4KM, UK
| | - Hassane El-Mkami
- Wellcome Trust Centre for Gene Regulation and Expression, Nucleic Acid Structure Research Group, College of Life Sciences, University of Dundee, Dundee DD1 5EH and School of Physics and Astronomy, University of St Andrews, St Andrews FE2 4KM, UK
| | - Tom Owen-Hughes
- Wellcome Trust Centre for Gene Regulation and Expression, Nucleic Acid Structure Research Group, College of Life Sciences, University of Dundee, Dundee DD1 5EH and School of Physics and Astronomy, University of St Andrews, St Andrews FE2 4KM, UK
| | - David G. Norman
- Wellcome Trust Centre for Gene Regulation and Expression, Nucleic Acid Structure Research Group, College of Life Sciences, University of Dundee, Dundee DD1 5EH and School of Physics and Astronomy, University of St Andrews, St Andrews FE2 4KM, UK
| |
Collapse
|
11
|
Distance and dynamics determination by W-band DEER and W-band ST-EPR. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2009; 39:711-9. [PMID: 20012080 DOI: 10.1007/s00249-009-0565-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2009] [Revised: 07/30/2009] [Accepted: 11/12/2009] [Indexed: 10/20/2022]
Abstract
To explore high-field EPR in biological applications we have compared measurements of dynamics with X-band (9 GHz) and W-band (94 GHz) saturation transfer EPR (ST-EPR) and distance determination by X and W-band DEER. A fourfold increase of sensitivity was observed for W-band ST-EPR compared with X-band. The distance measurements at both fields showed very good agreement in both the average distances and in the distance distributions. Multifrequency EPR thus provides an additional experimental dimension to facilitate extraction of distance populations. However, the expected orientational selectivity of W-band DEER to determine the relative orientation of spins has not been realized, most likely because of the large orientational disorder of spin labels on the protein surface.
Collapse
|
12
|
Ghimire H, McCarrick RM, Budil DE, Lorigan GA. Significantly improved sensitivity of Q-band PELDOR/DEER experiments relative to X-band is observed in measuring the intercoil distance of a leucine zipper motif peptide (GCN4-LZ). Biochemistry 2009; 48:5782-4. [PMID: 19476379 DOI: 10.1021/bi900781u] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Pulsed electron double resonance (PELDOR)/double electron-electron resonance (DEER) spectroscopy is a very powerful structural biology tool in which the dipolar coupling between two unpaired electron spins (site-directed nitroxide spin-labels) is measured. These measurements are typically conducted at X-band (9.4 GHz) microwave excitation using the four-pulse DEER sequence and can often require up to 12 h of signal averaging for biological samples (depending on the spin-label concentration). In this work, we present for the first time a substantial increase in DEER sensitivity obtained by collecting DEER spectra at Q-band (34 GHz), when compared to X-band. The huge boost in sensitivity (factor of 13) demonstrated at Q-band represents a 169-fold decrease in data collection time, reveals a greatly improved frequency spectrum and higher-quality distance data, and significantly increases sample throughput. Thus, the availability of Q-band DEER spectroscopy should have a major impact on structural biology studies using site-directed spin labeling EPR techniques.
Collapse
|
13
|
Alper SL. Molecular physiology and genetics of Na+-independent SLC4 anion exchangers. J Exp Biol 2009; 212:1672-83. [PMID: 19448077 PMCID: PMC2683012 DOI: 10.1242/jeb.029454] [Citation(s) in RCA: 170] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/12/2009] [Indexed: 01/12/2023]
Abstract
Plasmalemmal Cl(-)/HCO(3)(-) exchangers are encoded by the SLC4 and SLC26 gene superfamilies, and function to regulate intracellular pH, [Cl(-)] and cell volume. The Cl(-)/HCO(3)(-) exchangers of polarized epithelial cells also contribute to transepithelial secretion and reabsorption of acid-base equivalents and Cl(-). This review focuses on Na(+)-independent electroneutral Cl(-)/HCO(3)(-) exchangers of the SLC4 family. Human SLC4A1/AE1 mutations cause the familial erythroid disorders of spherocytic anemia, stomatocytic anemia and ovalocytosis. A largely discrete set of AE1 mutations causes familial distal renal tubular acidosis. The Slc4a2/Ae2(-/-) mouse dies before weaning with achlorhydria and osteopetrosis. A hypomorphic Ae2(-/-) mouse survives to exhibit male infertility with defective spermatogenesis and a syndrome resembling primary biliary cirrhosis. A human SLC4A3/AE3 polymorphism is associated with seizure disorder, and the Ae3(-/-) mouse has increased seizure susceptibility. The transport mechanism of mammalian SLC4/AE polypeptides is that of electroneutral Cl(-)/anion exchange, but trout erythroid Ae1 also mediates Cl(-) conductance. Erythroid Ae1 may mediate the DIDS-sensitive Cl(-) conductance of mammalian erythrocytes, and, with a single missense mutation, can mediate electrogenic SO(4)(2-)/Cl(-) exchange. AE1 trafficking in polarized cells is regulated by phosphorylation and by interaction with other proteins. AE2 exhibits isoform-specific patterns of acute inhibition by acidic intracellular pH and independently by acidic extracellular pH. In contrast, AE2 is activated by hypertonicity and, in a pH-independent manner, by ammonium and by hypertonicity. A growing body of structure-function and interaction data, together with emerging information about physiological function and structure, is advancing our understanding of SLC4 anion exchangers.
Collapse
Affiliation(s)
- Seth L Alper
- Renal Division and Molecular and Vascular Medicine Unit, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA.
| |
Collapse
|
14
|
Satchwell TJ, Shoemark DK, Sessions RB, Toye AM. Protein 4.2 : A complex linker. Blood Cells Mol Dis 2009; 42:201-10. [DOI: 10.1016/j.bcmd.2009.01.005] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2008] [Revised: 12/18/2008] [Accepted: 01/06/2009] [Indexed: 11/16/2022]
|
15
|
Antoniou C, Fung LM. Potential artifacts in using a glutathione S-transferase fusion protein system and spin labeling electron paramagnetic resonance methods to study protein-protein interactions. Anal Biochem 2008; 376:160-2. [PMID: 18316034 PMCID: PMC2423815 DOI: 10.1016/j.ab.2008.02.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2007] [Revised: 01/10/2008] [Accepted: 02/01/2008] [Indexed: 11/24/2022]
Abstract
Site-directed spin labeling electron paramagnetic resonance methods have been an important tool in studying protein-protein interactions. Labels are often attached to a cysteine residue, and spectra are acquired with and without binding partner(s) to provide information on the binding. This requires a knowledge of the label location which is simplified if the label remains faithfully attached to the designated residue in the complex. We report a system where this is not the case because the label was extracted by dialysis-resistant glutathione molecules. Once this artifact is identified, spectral subtraction provides a solution for meaningful data interpretation.
Collapse
Affiliation(s)
- Chloe Antoniou
- Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street., MC 111, Chicago, IL, 60607, USA
| | - L.W.-M. Fung
- Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street., MC 111, Chicago, IL, 60607, USA
| |
Collapse
|