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Tasak M, Phizicky EM. Initiator tRNA lacking 1-methyladenosine is targeted by the rapid tRNA decay pathway in evolutionarily distant yeast species. PLoS Genet 2022; 18:e1010215. [PMID: 35901126 PMCID: PMC9362929 DOI: 10.1371/journal.pgen.1010215] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Revised: 08/09/2022] [Accepted: 07/05/2022] [Indexed: 11/18/2022] Open
Abstract
All tRNAs have numerous modifications, lack of which often results in growth defects in the budding yeast Saccharomyces cerevisiae and neurological or other disorders in humans. In S. cerevisiae, lack of tRNA body modifications can lead to impaired tRNA stability and decay of a subset of the hypomodified tRNAs. Mutants lacking 7-methylguanosine at G46 (m7G46), N2,N2-dimethylguanosine (m2,2G26), or 4-acetylcytidine (ac4C12), in combination with other body modification mutants, target certain mature hypomodified tRNAs to the rapid tRNA decay (RTD) pathway, catalyzed by 5’-3’ exonucleases Xrn1 and Rat1, and regulated by Met22. The RTD pathway is conserved in the phylogenetically distant fission yeast Schizosaccharomyces pombe for mutants lacking m7G46. In contrast, S. cerevisiae trm6/gcd10 mutants with reduced 1-methyladenosine (m1A58) specifically target pre-tRNAiMet(CAU) to the nuclear surveillance pathway for 3’-5’ exonucleolytic decay by the TRAMP complex and nuclear exosome. We show here that the RTD pathway has an unexpected major role in the biology of m1A58 and tRNAiMet(CAU) in both S. pombe and S. cerevisiae. We find that S. pombe trm6Δ mutants lacking m1A58 are temperature sensitive due to decay of tRNAiMet(CAU) by the RTD pathway. Thus, trm6Δ mutants had reduced levels of tRNAiMet(CAU) and not of eight other tested tRNAs, overexpression of tRNAiMet(CAU) restored growth, and spontaneous suppressors that restored tRNAiMet(CAU) levels had mutations in dhp1/RAT1 or tol1/MET22. In addition, deletion of cid14/TRF4 in the nuclear surveillance pathway did not restore growth. Furthermore, re-examination of S. cerevisiae trm6 mutants revealed a major role of the RTD pathway in maintaining tRNAiMet(CAU) levels, in addition to the known role of the nuclear surveillance pathway. These findings provide evidence for the importance of m1A58 in the biology of tRNAiMet(CAU) throughout eukaryotes, and fuel speculation that the RTD pathway has a major role in quality control of body modification mutants throughout fungi and other eukaryotes.
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Affiliation(s)
- Monika Tasak
- Department of Biochemistry and Biophysics, Center for RNA Biology, University of Rochester School of Medicine, Rochester, New York, United States of America
| | - Eric M. Phizicky
- Department of Biochemistry and Biophysics, Center for RNA Biology, University of Rochester School of Medicine, Rochester, New York, United States of America
- * E-mail:
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2
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Shirzadian-Khorramabad R, Moazzenzadeh T, Sajedi RH, Jing HC, Hille J, Dijkwel PP. A mutation in Arabidopsis SAL1 alters its in vitro activity against IP 3 and delays developmental leaf senescence in association with lower ROS levels. PLANT MOLECULAR BIOLOGY 2022; 108:549-563. [PMID: 35122174 DOI: 10.1007/s11103-022-01245-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Accepted: 01/21/2022] [Indexed: 06/14/2023]
Abstract
Our manuscript is the first to find a link between activity of SAL1/OLD101 against IP3 and plant leaf senescence regulation and ROS levels assigning a potential biological role for IP3. Leaf senescence is a genetically programmed process that limits the longevity of a leaf. We identified and analyzed the recessive Arabidopsis stay-green mutation onset of leaf death 101 (old101). Developmental leaf longevity is extended in old101 plants, which coincided with higher peroxidase activity and decreased H2O2 levels in young 10-day-old, but not 25-day-old plants. The old101 phenotype is caused by a point mutation in SAL1, which encodes a bifunctional enzyme with inositol polyphosphate-1-phosphatase and 3' (2'), 5'-bisphosphate nucleotidase activity. SAL1 activity is highly specific for its substrates 3-polyadenosine 5-phosphate (PAP) and inositol 1, 4, 5-trisphosphate (IP3), where it removes the 1-phosphate group from the IP3 second messenger. The in vitro activity of recombinant old101 protein against its substrate IP3 was 2.5-fold lower than that of wild type SAL1 protein. However, the in vitro activity of recombinant old101 mutant protein against PAP remained the same as that of the wild type SAL1 protein. The results open the possibility that the activity of SAL1 against IP3 may affect the redox balance of young seedlings and that this delays the onset of leaf senescence.
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Affiliation(s)
- Reza Shirzadian-Khorramabad
- Department of Agricultural Biotechnology, Faculty of Agricultural Sciences, University of Guilan, Rasht, Iran.
- Molecular Biology of Plants, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Kerklaan 30, 9751 NN, Haren, The Netherlands.
- School of Fundamental Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand.
| | - Taghi Moazzenzadeh
- Department of Agricultural Biotechnology, Faculty of Agricultural Sciences, University of Guilan, Rasht, Iran
- MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE, Enschede, The Netherlands
| | - Reza H Sajedi
- Department of Biochemistry, Faculty of Biological Sciences, Tarbiat Modares University, Tehran, Iran
| | - Hai-Chun Jing
- Molecular Biology of Plants, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Kerklaan 30, 9751 NN, Haren, The Netherlands
- Key Laboratory of Plant Resources, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
| | - Jacques Hille
- Molecular Biology of Plants, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Kerklaan 30, 9751 NN, Haren, The Netherlands
| | - Paul P Dijkwel
- Molecular Biology of Plants, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Kerklaan 30, 9751 NN, Haren, The Netherlands
- School of Fundamental Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand
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3
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Dollins DE, Xiong JP, Endo-Streeter S, Anderson DE, Bansal VS, Ponder JW, Ren Y, York JD. A structural basis for lithium and substrate binding of an inositide phosphatase. J Biol Chem 2021; 296:100059. [PMID: 33172890 PMCID: PMC7948987 DOI: 10.1074/jbc.ra120.014057] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 10/29/2020] [Accepted: 11/10/2020] [Indexed: 01/07/2023] Open
Abstract
Inositol polyphosphate 1-phosphatase (INPP1) is a prototype member of metal-dependent/lithium-inhibited phosphomonoesterase protein family defined by a conserved three-dimensional core structure. Enzymes within this family function in distinct pathways including inositide signaling, gluconeogenesis, and sulfur assimilation. Using structural and biochemical studies, we report the effect of substrate and lithium on a network of metal binding sites within the catalytic center of INPP1. We find that lithium preferentially occupies a key site involved in metal-activation only when substrate or product is added. Mutation of a conserved residue that selectively coordinates the putative lithium-binding site results in a dramatic 100-fold reduction in the inhibitory constant as compared with wild-type. Furthermore, we report the INPP1/inositol 1,4-bisphosphate complex which illuminates key features of the enzyme active site. Our results provide insights into a structural basis for uncompetitive lithium inhibition and substrate recognition and define a sequence motif for metal binding within this family of regulatory phosphatases.
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Affiliation(s)
- D Eric Dollins
- Department of Pharmacology and Cancer Biology, Duke University, Durham, North Carolina, USA
| | - Jian-Ping Xiong
- Department of Pharmacology and Cancer Biology, Duke University, Durham, North Carolina, USA
| | - Stuart Endo-Streeter
- Department of Pharmacology and Cancer Biology, Duke University, Durham, North Carolina, USA
| | - David E Anderson
- Department of Pharmacology and Cancer Biology, Duke University, Durham, North Carolina, USA
| | - Vinay S Bansal
- Department of Biochemistry, Vanderbilt University, Nashville, Tennessee, USA
| | - Jay W Ponder
- Department of Chemistry, Washington University, St Louis, Missouri, USA
| | - Yi Ren
- Department of Biochemistry, Vanderbilt University, Nashville, Tennessee, USA
| | - John D York
- Department of Pharmacology and Cancer Biology, Duke University, Durham, North Carolina, USA; Department of Biochemistry, Vanderbilt University, Nashville, Tennessee, USA.
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4
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Jakobsson E, Argüello-Miranda O, Chiu SW, Fazal Z, Kruczek J, Nunez-Corrales S, Pandit S, Pritchet L. Towards a Unified Understanding of Lithium Action in Basic Biology and its Significance for Applied Biology. J Membr Biol 2017; 250:587-604. [PMID: 29127487 PMCID: PMC5696506 DOI: 10.1007/s00232-017-9998-2] [Citation(s) in RCA: 91] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2017] [Accepted: 10/21/2017] [Indexed: 01/14/2023]
Abstract
Lithium has literally been everywhere forever, since it is one of the three elements created in the Big Bang. Lithium concentration in rocks, soil, and fresh water is highly variable from place to place, and has varied widely in specific regions over evolutionary and geologic time. The biological effects of lithium are many and varied. Based on experiments in which animals are deprived of lithium, lithium is an essential nutrient. At the other extreme, at lithium ingestion sufficient to raise blood concentration significantly over 1 mM/, lithium is acutely toxic. There is no consensus regarding optimum levels of lithium intake for populations or individuals-with the single exception that lithium is a generally accepted first-line therapy for bipolar disorder, and specific dosage guidelines for sufferers of that condition are generally agreed on. Epidemiological evidence correlating various markers of social dysfunction and disease vs. lithium level in drinking water suggest benefits of moderately elevated lithium compared to average levels of lithium intake. In contrast to other biologically significant ions, lithium is unusual in not having its concentration in fluids of multicellular animals closely regulated. For hydrogen ions, sodium ions, potassium ions, calcium ions, chloride ions, and magnesium ions, blood and extracellular fluid concentrations are closely and necessarily regulated by systems of highly selective channels, and primary and secondary active transporters. Lithium, while having strong biological activity, is tolerated over body fluid concentrations ranging over many orders of magnitude. The lack of biological regulation of lithium appears due to lack of lithium-specific binding sites and selectivity filters. Rather lithium exerts its myriad physiological and biochemical effects by competing for macromolecular sites that are relatively specific for other cations, most especially for sodium and magnesium. This review will consider what is known about the nature of this competition and suggest using and extending this knowledge towards the goal of a unified understanding of lithium in biology and the application of that understanding in medicine and nutrition.
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Affiliation(s)
- Eric Jakobsson
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
- Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
- Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
- National Center for Supercomputing Applications, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
| | | | - See-Wing Chiu
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
- National Center for Supercomputing Applications, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Zeeshan Fazal
- Department of Biosciences, COMSATS Institute of Information Technology, Islamabad, Pakistan
- Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - James Kruczek
- Department of Physics, University of South Florida, Tampa, FL, USA
| | - Santiago Nunez-Corrales
- National Center for Supercomputing Applications, University of Illinois at Urbana-Champaign, Urbana, IL, USA
- Illinois Informatics Institute, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Sagar Pandit
- Department of Physics, University of South Florida, Tampa, FL, USA
| | - Laura Pritchet
- Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, IL, USA
- Department of Psychological and Brain Sciences, University of California at Santa Barbara, Santa Barbara, CA, USA
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5
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Sensing and signaling of oxidative stress in chloroplasts by inactivation of the SAL1 phosphoadenosine phosphatase. Proc Natl Acad Sci U S A 2016; 113:E4567-76. [PMID: 27432987 PMCID: PMC4978270 DOI: 10.1073/pnas.1604936113] [Citation(s) in RCA: 124] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Intracellular signaling during oxidative stress is complex, with organelle-to-nucleus retrograde communication pathways ill-defined or incomplete. Here we identify the 3'-phosphoadenosine 5'-phosphate (PAP) phosphatase SAL1 as a previously unidentified and conserved oxidative stress sensor in plant chloroplasts. Arabidopsis thaliana SAL1 (AtSAL1) senses changes in photosynthetic redox poise, hydrogen peroxide, and superoxide concentrations in chloroplasts via redox regulatory mechanisms. AtSAL1 phosphatase activity is suppressed by dimerization, intramolecular disulfide formation, and glutathionylation, allowing accumulation of its substrate, PAP, a chloroplast stress retrograde signal that regulates expression of plastid redox associated nuclear genes (PRANGs). This redox regulation of SAL1 for activation of chloroplast signaling is conserved in the plant kingdom, and the plant protein has evolved enhanced redox sensitivity compared with its yeast ortholog. Our results indicate that in addition to sulfur metabolism, SAL1 orthologs have evolved secondary functions in oxidative stress sensing in the plant kingdom.
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6
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Meisel JD, Kim DH. Inhibition of Lithium-Sensitive Phosphatase BPNT-1 Causes Selective Neuronal Dysfunction in C. elegans. Curr Biol 2016; 26:1922-8. [PMID: 27397889 DOI: 10.1016/j.cub.2016.05.050] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Revised: 05/09/2016] [Accepted: 05/19/2016] [Indexed: 11/26/2022]
Abstract
Lithium has been a mainstay for the treatment of bipolar disorder, yet the molecular mechanisms underlying its action remain enigmatic. Bisphosphate 3'-nucleotidase (BPNT-1) is a lithium-sensitive phosphatase that catalyzes the breakdown of cytosolic 3'-phosphoadenosine 5'-phosphate (PAP), a byproduct of sulfation reactions utilizing the universal sulfate group donor 3'-phosphoadenosine 5'-phosphosulfate (PAPS) [1-3]. Loss of BPNT-1 leads to the toxic accumulation of PAP in yeast and non-neuronal cell types in mice [4, 5]. Intriguingly, BPNT-1 is expressed throughout the mammalian brain [4], and it has been hypothesized that inhibition of BPNT-1 could contribute to the effects of lithium on behavior [5]. Here, we show that loss of BPNT-1 in Caenorhabditis elegans results in the selective dysfunction of two neurons, the bilaterally symmetric pair of ASJ chemosensory neurons. As a result, BPNT-1 mutants are defective in behaviors dependent on the ASJ neurons, such as dauer exit and pathogen avoidance. Acute treatment with lithium also causes dysfunction of the ASJ neurons, and we show that this effect is reversible and mediated specifically through inhibition of BPNT-1. Finally, we show that the selective effect of lithium on the nervous system is due in part to the limited expression of the cytosolic sulfotransferase SSU-1 in the ASJ neuron pair. Our data suggest that lithium, through inhibition of BPNT-1 in the nervous system, can cause selective toxicity to specific neurons, resulting in corresponding effects on behavior of C. elegans.
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Affiliation(s)
- Joshua D Meisel
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139 USA
| | - Dennis H Kim
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139 USA.
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7
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Bhattacharyya S, Dutta A, Dutta D, Ghosh AK, Das AK. Structural elucidation of the NADP(H) phosphatase activity of staphylococcal dual-specific IMPase/NADP(H) phosphatase. ACTA CRYSTALLOGRAPHICA SECTION D-STRUCTURAL BIOLOGY 2016; 72:281-90. [PMID: 26894675 DOI: 10.1107/s2059798316000620] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Accepted: 01/12/2016] [Indexed: 11/10/2022]
Abstract
NADP(H)/NAD(H) homeostasis has long been identified to play a pivotal role in the mitigation of reactive oxygen stress (ROS) in the intracellular milieu and is therefore critical for the progression and pathogenesis of many diseases. NAD(H) kinases and NADP(H) phosphatases are two key players in this pathway. Despite structural evidence demonstrating the existence and mode of action of NAD(H) kinases, the specific annotation and the mode of action of NADP(H) phosphatases remains obscure. Here, structural evidence supporting the alternative role of inositol monophosphatase (IMPase) as an NADP(H) phosphatase is reported. Crystal structures of staphylococcal dual-specific IMPase/NADP(H) phosphatase (SaIMPase-I) in complex with the substrates D-myo-inositol-1-phosphate and NADP(+) have been solved. The structure of the SaIMPase-I-Ca(2+)-NADP(+) ternary complex reveals the catalytic mode of action of NADP(H) phosphatase. Moreover, structures of SaIMPase-I-Ca(2+)-substrate complexes have reinforced the earlier proposal that the length of the active-site-distant helix α4 and its preceding loop are the predisposing factors for the promiscuous substrate specificity of SaIMPase-I. Altogether, the evidence presented suggests that IMPase-family enzymes with a shorter α4 helix could be potential candidates for previously unreported NADP(H) phosphatase activity.
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Affiliation(s)
- Sudipta Bhattacharyya
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721 302, India
| | - Anirudha Dutta
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721 302, India
| | - Debajyoti Dutta
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721 302, India
| | - Ananta Kumar Ghosh
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721 302, India
| | - Amit Kumar Das
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721 302, India
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8
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Yenush L. Potassium and Sodium Transport in Yeast. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 892:187-228. [DOI: 10.1007/978-3-319-25304-6_8] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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9
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Erickson AI, Sarsam RD, Fisher AJ. Crystal Structures of Mycobacterium tuberculosis CysQ, with Substrate and Products Bound. Biochemistry 2015; 54:6830-41. [PMID: 26512869 DOI: 10.1021/acs.biochem.5b01000] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
In many organisms, 3'-phosphoadenosine 5'-phosphate (PAP) is a product of two reactions in the sulfur activation pathway. The sulfurylation of biomolecules, catalyzed by sulfotransferases, uses 3'-phosphoadenosine 5'-phosphosulfate (PAPS) as a sulfate donor, producing the sulfated biomolecule and PAP product. Additionally, the first step in sulfate reduction for many bacteria and fungi reduces the sulfate moiety of PAPS, producing PAP and sulfite, which is subsequently reduced to sulfide. PAP is removed by the phosphatase activity of CysQ, a 3',5'-bisphosphate nucleotidase, yielding AMP and phosphate. Because excess PAP alters the equilibrium of the sulfur pathway and inhibits sulfotransferases, PAP concentrations can affect the levels of sulfur-containing metabolites. Therefore, CysQ, a divalent cation metal-dependent phosphatase, is a major regulator of this pathway. CysQ (Rv2131c) from Mycobacterium tuberculosis (Mtb) was successfully expressed, purified, and crystallized in a variety of ligand-bound states. Here we report six crystal structures of Mtb CysQ, including a ligand-free structure, a lithium-inhibited state with substrate PAP bound, and a product-bound complex with AMP, phosphate, and three Mg(2+) ions bound. Comparison of these structures together with homologues of the superfamily has provided insight into substrate specificity, metal coordination, and catalytic mechanism.
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Affiliation(s)
- Anna I Erickson
- Department of Chemistry, ‡Department of Molecular and Cellular Biology, and §Graduate Program in Biochemistry and Molecular, Cellular and Developmental Biology, University of California , One Shields Avenue, Davis, California 95616, United States
| | - Reta D Sarsam
- Department of Chemistry, ‡Department of Molecular and Cellular Biology, and §Graduate Program in Biochemistry and Molecular, Cellular and Developmental Biology, University of California , One Shields Avenue, Davis, California 95616, United States
| | - Andrew J Fisher
- Department of Chemistry, ‡Department of Molecular and Cellular Biology, and §Graduate Program in Biochemistry and Molecular, Cellular and Developmental Biology, University of California , One Shields Avenue, Davis, California 95616, United States
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10
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Volkov V. Quantitative description of ion transport via plasma membrane of yeast and small cells. FRONTIERS IN PLANT SCIENCE 2015; 6:425. [PMID: 26113853 PMCID: PMC4462678 DOI: 10.3389/fpls.2015.00425] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Accepted: 05/26/2015] [Indexed: 05/21/2023]
Abstract
Modeling of ion transport via plasma membrane needs identification and quantitative understanding of the involved processes. Brief characterization of main ion transport systems of a yeast cell (Pma1, Ena1, TOK1, Nha1, Trk1, Trk2, non-selective cation conductance) and determining the exact number of molecules of each transporter per a typical cell allow us to predict the corresponding ion flows. In this review a comparison of ion transport in small yeast cell and several animal cell types is provided. The importance of cell volume to surface ratio is emphasized. The role of cell wall and lipid rafts is discussed in respect to required increase in spatial and temporary resolution of measurements. Conclusions are formulated to describe specific features of ion transport in a yeast cell. Potential directions of future research are outlined based on the assumptions.
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Affiliation(s)
- Vadim Volkov
- *Correspondence: Vadim Volkov, Faculty of Life Sciences, School of Human Sciences, London Metropolitan University, 166-220 Holloway Road, London N7 8DB, UK
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11
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Faisal Tarique K, Arif Abdul Rehman S, Betzel C, Gourinath S. Structure-based identification of inositol polyphosphate 1-phosphatase from Entamoeba histolytica. ACTA ACUST UNITED AC 2014; 70:3023-33. [PMID: 25372691 DOI: 10.1107/s1399004714021245] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2014] [Accepted: 09/24/2014] [Indexed: 12/30/2022]
Abstract
Inositol polyphosphate 1-phosphatase from Entamoeba histolytica (EhIPPase) is an Mg(2+)-dependent and Li(+)-sensitive enzyme that catalyzes the hydrolysis of inositol 1,4-bisphosphate [Ins(1,4)P2] into myo-inositol 1-monophosphate and PO4(3-). In the present work, EhIPPase has been biochemically identified and its crystal structure has been determined in the presence of Mg(2+) and PO4(3-) at 2.5 Å resolution. This enzyme was previously classified as a 3'(2'),5'-bisphosphate nucleotidase in the NCBI, but its biochemical activity and structural analysis suggest that this enzyme behaves more like an inositol polyphosphate 1-phosphatase. The ability of EhIPPase to hydrolyze the smaller Ins(1,4)P2 better than the bulkier 3'-phosphoadenosine 5'-phosphate (PAP) is explained on the basis of the orientations of amino-acid residues in the binding site. This structure is the first of its class to be determined from any protozoan parasite, and is the third to determined among all organisms, following its rat and bovine homologues. The three-dimensional fold of EhIPPase is similar to those of other members of the inositol monophosphatase superfamily, which also includes inositol monophosphatase, 3'(2'),5'-bisphosphate nucleotidase and fructose-1,6-bisphosphate 1-phosphatase. They all share conserved residues essential for metal binding and substrate hydrolysis, with the motif D-Xn-EE-Xn-DP(I/L)DG(S/T)-Xn-WD-Xn-GG. The structure is divided into two domains, namely α+β and α/β, and the substrate and metal ions bind between them. However, the ability of each enzyme class to act specifically on its cognate substrate is governed by the class-specific amino-acid residues at the active site.
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Affiliation(s)
| | | | - Christian Betzel
- Laboratory for Structural Biology of Infection and Inflammation, Department of Chemistry, c/o DESY, University of Hamburg, Notkestrasse 85, 22603 Hamburg, Germany
| | - Samudrala Gourinath
- School of Life Sciences, Jawaharlal Nehru University, New Delhi 110 067, India
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12
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Dutta A, Bhattacharyya S, Dutta D, Das AK. Structural elucidation of the binding site and mode of inhibition of Li+and Mg2+in inositol monophosphatase. FEBS J 2014; 281:5309-24. [PMID: 25263816 DOI: 10.1111/febs.13070] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Revised: 09/16/2014] [Accepted: 09/23/2014] [Indexed: 01/20/2023]
Affiliation(s)
- Anirudha Dutta
- Department of Biotechnology; Indian Institute of Technology Kharagpur; Kharagpur West Bengal India
| | - Sudipta Bhattacharyya
- Department of Biotechnology; Indian Institute of Technology Kharagpur; Kharagpur West Bengal India
| | - Debajyoti Dutta
- Department of Biotechnology; Indian Institute of Technology Kharagpur; Kharagpur West Bengal India
| | - Amit Kumar Das
- Department of Biotechnology; Indian Institute of Technology Kharagpur; Kharagpur West Bengal India
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13
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Gil R, Bautista I, Boscaiu M, Lidón A, Wankhade S, Sánchez H, Llinares J, Vicente O. Responses of five Mediterranean halophytes to seasonal changes in environmental conditions. AOB PLANTS 2014; 6:plu049. [PMID: 25139768 PMCID: PMC4163002 DOI: 10.1093/aobpla/plu049] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Accepted: 07/16/2014] [Indexed: 05/23/2023]
Abstract
In their natural habitats, different mechanisms may contribute to the tolerance of halophytes to high soil salinity and other abiotic stresses, but their relative contribution and ecological relevance, for a given species, remain largely unknown. We studied the responses to changing environmental conditions of five halophytes (Sarcocornia fruticosa, Inula crithmoides, Plantago crassifolia, Juncus maritimus and J. acutus) in a Mediterranean salt marsh, from summer 2009 to autumn 2010. A principal component analysis was used to correlate soil and climatic data with changes in the plants' contents of chemical markers associated with stress responses: ions, osmolytes, malondialdehyde (MDA, a marker of oxidative stress) and antioxidant systems. Stress tolerance in S. fruticosa, I. crithmoides and P. crassifolia (all succulent dicots) seemed to depend mostly on the transport of ions to aerial parts and the biosynthesis of specific osmolytes, whereas both Juncus species (monocots) were able to avoid accumulation of toxic ions, maintaining relatively high K(+)/Na(+) ratios. For the most salt-tolerant taxa (S. fruticosa and I. crithmoides), seasonal variations of Na(+), Cl(-), K(+) and glycine betaine, their major osmolyte, did not correlate with environmental parameters associated with salt or water stress, suggesting that their tolerance mechanisms are constitutive and relatively independent of external conditions, although they could be mediated by changes in the subcellular compartmentalization of ions and compatible osmolytes. Proline levels were too low in all the species to possibly have any effect on osmotic adjustment. However-except for P. crassifolia-proline may play a role in stress tolerance based on its 'osmoprotectant' functions. No correlation was observed between the degree of environmental stress and the levels of MDA or enzymatic and non-enzymatic antioxidants, indicating that the investigated halophytes are not subjected to oxidative stress under natural conditions and do not, therefore, need to activate antioxidant defence mechanisms.
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Affiliation(s)
- Ricardo Gil
- Instituto de Biología Molecular y Celular de Plantas (UPV-CSIC), Universitat Politècnica de València, Camino de Vera s/n, 46022 Valencia, Spain
| | - Inmaculada Bautista
- ReForest, Departamento de Ingeniería Hidráulica y Medio Ambiente, Universitat Politècnica de València, Camino de Vera s/n, 46022 Valencia, Spain
| | - Monica Boscaiu
- Instituto Agroforestal Mediterráneo (IAM), Universitat Politècnica de València, Camino de Vera s/n, 46022 Valencia, Spain
| | - Antonio Lidón
- ReForest, Departamento de Ingeniería Hidráulica y Medio Ambiente, Universitat Politècnica de València, Camino de Vera s/n, 46022 Valencia, Spain
| | - Shantanu Wankhade
- Instituto de Biología Molecular y Celular de Plantas (UPV-CSIC), Universitat Politècnica de València, Camino de Vera s/n, 46022 Valencia, Spain
| | - Héctor Sánchez
- Instituto de Biología Molecular y Celular de Plantas (UPV-CSIC), Universitat Politècnica de València, Camino de Vera s/n, 46022 Valencia, Spain
| | - Josep Llinares
- Instituto de Investigación para la Gestión Integral de Zonas Costeras (IGIC), Universitat Politècnica de València, C/Paranimf 1, 46730 Grao de Gandia, Valencia, Spain
| | - Oscar Vicente
- Instituto de Biología Molecular y Celular de Plantas (UPV-CSIC), Universitat Politècnica de València, Camino de Vera s/n, 46022 Valencia, Spain
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14
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Faisal Tarique K, Arif Abdul Rehman S, Gourinath S. Structural elucidation of a dual-activity PAP phosphatase-1 from Entamoeba histolytica capable of hydrolysing both 3'-phosphoadenosine 5'-phosphate and inositol 1,4-bisphosphate. ACTA ACUST UNITED AC 2014; 70:2019-31. [PMID: 25004978 DOI: 10.1107/s1399004714010268] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2014] [Accepted: 05/06/2014] [Indexed: 12/28/2022]
Abstract
The enzyme 3'-phosphoadenosine 5'-phosphatase-1 (PAP phosphatase-1) is a member of the Li(+)-sensitive Mg(2+)-dependent phosphatase superfamily, or inositol monophosphatase (IMPase) superfamily, and is an important regulator of the sulfate-activation pathway in all living organisms. Inhibition of this enzyme leads to accumulation of the toxic byproduct 3'-phosphoadenosine 5'-phosphate (PAP), which could be lethal to the organism. Genomic analysis of Entamoeba histolytica suggests the presence of two isoforms of PAP phosphatase. The PAP phosphatase-1 isoform of this organism is shown to be active over wide ranges of pH and temperature. Interestingly, this enzyme is inhibited by submillimolar concentrations of Li(+), while being insensitive to Na(+). Interestingly, the enzyme showed activity towards both PAP and inositol 1,4-bisphosphate and behaved as an inositol polyphosphate 1-phosphatase. Crystal structures of this enzyme in its native form and in complex with adenosine 5'-monophosphate have been determined to 2.1 and 2.6 Å resolution, respectively. The PAP phosphatase-1 structure is divided into two domains, namely α+β and α/β, and the substrate and metal ions bind between them. This is a first structure of any PAP phosphatase to be determined from a human parasitic protozoan. This enzyme appears to function using a mechanism involving three-metal-ion assisted catalysis. Comparison with other structures indicates that the sensitivity to alkali-metal ions may depend on the orientation of a specific catalytic loop.
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Affiliation(s)
| | | | - S Gourinath
- School of Life Sciences, Jawaharlal Nehru University, New Delhi 110 067, India
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15
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Yeast 3',5'-bisphosphate nucleotidase: an affinity tag for protein purification. Protein Expr Purif 2014; 97:81-7. [PMID: 24613729 DOI: 10.1016/j.pep.2014.02.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Revised: 02/23/2014] [Accepted: 02/25/2014] [Indexed: 11/22/2022]
Abstract
Affinity chromatography is one of the most popular methods for protein purification. Each tag method has its advantages and disadvantages, and combination of different tags and developing of new tags had been proposed and performed. Yeast 3',5'-bisphosphate nucleotidase, also known as HAL2, hydrolyzes 3'-phosphoadenosine 5'-phosphate (PAP) with submicromolar Km, which indicated the tight interactions between HAL2 and PAP. In order to explore the feasibility of HAL2 as a protein purification affinity tag, HAL2 was further characterized with PAP as substrate. Results demonstrated that KmPAP and kcatPAP were ∼0.3μM and ∼11s(-)(1), respectively. Kd for PAP was 0.008μM in the presence of Ca(2+). pH was also found to affect interactions between HAL2 and PAP, with tightest binding (Kd∼8nM) at pH 7.5 and 8. The purification protocol was rationally designed based on nanomolar affinity to PAP agarose in the presence of Ca(2+), which could satisfy the metal requirement for PAP binding, prevent hydrolysis of immobilized PAP and could be chelated by ethylene glycol tetraacetic acid (EGTA) for elution. A series of expression vectors were further constructed and Escherichia coli adenosine 5'-phosphosulfate kinase (APSK) was prokaryotically expressed, purified and characterized. Ready to use expression vector with eight commonly used restriction enzyme recognition sites in multiple cloning site was subsequently constructed. By comparing with current popular tags, HAL2 was found to be an efficient and economical tag for prokaryotic protein expression and purification.
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16
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Gašparič MB, Lenassi M, Gostinčar C, Rotter A, Plemenitaš A, Gunde-Cimerman N, Gruden K, Žel J. Insertion of a specific fungal 3'-phosphoadenosine-5'-phosphatase motif into a plant homologue improves halotolerance and drought tolerance of plants. PLoS One 2013; 8:e81872. [PMID: 24349144 PMCID: PMC3857206 DOI: 10.1371/journal.pone.0081872] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Accepted: 10/20/2013] [Indexed: 01/05/2023] Open
Abstract
Soil salinity and drought are among the most serious agricultural and environmental problems of today. Therefore, investigations of plant resistance to abiotic stress have received a lot of attention in recent years. In this study, we identified the complete coding sequence of a 3′-phosphoadenosine-5′-phosphatase protein, ApHal2, from the halotolerant yeast Aureobasidium pullulans. Expression of the ApHAL2 gene in a Saccharomyces cerevisiae hal2 mutant complemented the mutant auxotrophy for methionine, and rescued the growth of the hal2 mutant in media with high NaCl concentrations. A 21-amino-acids-long region of the ApHal2 enzyme was inserted into the Arabidopsis thaliana homologue of Hal2, the SAL1 phosphatase. The inserted sequence included the META motif, which has previously been implicated in increased sodium tolerance of the Hal2 homologue from a related fungal species. Transgenic Arabidopsis plants overexpressing this modified SAL1 (mSAL1) showed improved halotolerance and drought tolerance. In a medium with an elevated salt concentration, mSAL1-expressing plants were twice as likely to have roots in a higher length category in comparison with the wild-type Arabidopsis and with plants overexpressing the native SAL1, and had 5% to 10% larger leaf surface area under moderate and severe salt stress, respectively. Similarly, after moderate drought exposure, the mSAL1-expressing plants showed 14% increased dry weight after revitalisation, with no increase in dry weight of the wild-type plants. With severe drought, plants overexpressing native SAL1 had the worst rehydration success, consistent with the recently proposed role of SAL1 in severe drought. This was not observed for plants expressing mSAL1. Therefore, the presence of this fungal META motif sequence is beneficial under conditions of increased salinity and moderate drought, and shows no drawbacks for plant survival under severe drought. This demonstrates that adaptations of extremotolerant fungi should be considered as a valuable resource for improving stress-tolerance in plant breeding in the future.
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Affiliation(s)
- Meti Buh Gašparič
- Department of Biotechnology and Systems Biology, National Institute of Biology, Ljubljana, Slovenia
| | - Metka Lenassi
- Institute of Biochemistry, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
- Centre of Excellence for Integrated Approaches in Chemistry and Biology of Proteins (CIPKeBiP), Ljubljana, Slovenia
| | - Cene Gostinčar
- Centre of Excellence for Integrated Approaches in Chemistry and Biology of Proteins (CIPKeBiP), Ljubljana, Slovenia
- Department of Biology, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia
| | - Ana Rotter
- Department of Biotechnology and Systems Biology, National Institute of Biology, Ljubljana, Slovenia
| | - Ana Plemenitaš
- Institute of Biochemistry, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Nina Gunde-Cimerman
- Centre of Excellence for Integrated Approaches in Chemistry and Biology of Proteins (CIPKeBiP), Ljubljana, Slovenia
| | - Kristina Gruden
- Department of Biotechnology and Systems Biology, National Institute of Biology, Ljubljana, Slovenia
| | - Jana Žel
- Department of Biotechnology and Systems Biology, National Institute of Biology, Ljubljana, Slovenia
- * E-mail:
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17
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Gutka HJ, Rukseree K, Wheeler PR, Franzblau SG, Movahedzadeh F. glpX gene of Mycobacterium tuberculosis: heterologous expression, purification, and enzymatic characterization of the encoded fructose 1,6-bisphosphatase II. Appl Biochem Biotechnol 2011; 164:1376-89. [PMID: 21451980 DOI: 10.1007/s12010-011-9219-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2010] [Accepted: 03/01/2011] [Indexed: 12/22/2022]
Abstract
The glpX gene (Rv1099c) of Mycobacterium tuberculosis (Mtb) encodes Fructose 1,6-bisphosphatase II (FBPase II; EC 3.1.3.11); a key gluconeogenic enzyme. Mtb possesses glpX homologue as the major known FBPase. This study explored the expression, purification and enzymatic characterization of functionally active FBPase II from Mtb. The glpX gene was cloned, expressed and purified using a two step purification strategy including affinity and size exclusion chromatography. The specific activity of Mtb FBPase II is 1.3 U/mg. The enzyme is oligomeric, followed Michaelis-Menten kinetics with an apparent km = 44 μM. Enzyme activity is dependent on bivalent metal ions and is inhibited by lithium and inorganic phosphate. The pH optimum and thermostability of the enzyme have been determined. The robust expression, purification and assay protocols ensure sufficient production of this protein for structural biology and screening of inhibitors against this enzyme.
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Affiliation(s)
- Hiten J Gutka
- Institute for Tuberculosis Research (M/C 964), College of Pharmacy, Room 412, University of Illinois at Chicago, 833 S. Wood St, Chicago, IL 60612-7231, USA
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18
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Abstract
RNA viruses are the champions of evolution due to high frequency mutations and genetic recombination occurring during virus replication. These genetic events are due to the error-prone nature of viral RNA-dependent RNA polymerases (RdRp). Recently emerging models on viral RNA recombination, however, also include key roles for host and environmental factors. Accordingly, genome-wide screens and global proteomics approaches with Tomato bushy stunt virus (TBSV) and yeast (Saccharomyces cerevisiae) as a model host have identified 38 host proteins affecting viral RNA recombination. Follow-up studies have identified key host proteins and cellular pathways involved in TBSV RNA recombination. In addition, environmental factors, such as salt stress, have been shown to affect TBSV recombination via influencing key host or viral factors involved in the recombination process. These advances will help build more accurate models on viral recombination, evolution, and adaptation.
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19
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Gostinčar C, Lenassi M, Gunde-Cimerman N, Plemenitaš A. Fungal adaptation to extremely high salt concentrations. ADVANCES IN APPLIED MICROBIOLOGY 2011; 77:71-96. [PMID: 22050822 DOI: 10.1016/b978-0-12-387044-5.00003-0] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Hypersaline environments support substantial microbial communities of selected halotolerant and halophilic organisms, including fungi from various orders. In hypersaline water of solar salterns, the black yeast Hortaea werneckii is by far the most successful fungal representative. It has an outstanding ability to overcome the turgor loss and sodium toxicity that are typical for hypersaline environments, which facilitates its growth even in solutions that are almost saturated with NaCl. We propose a model of cellular responses to high salt concentrations that integrates the current knowledge of H. werneckii adaptations. The negative impact of a hyperosmolar environment is counteracted by an increase in the energy supply that is needed to drive the energy-demanding export of ions and synthesis of compatible solutes. Changes in membrane lipid composition and cell-wall structure maintain the integrity and functioning of the stressed cells. Understanding the salt responses of H. werneckii and other fungi (e.g., the halophilic Wallemia ichthyophaga) will extend our knowledge of fungal stress tolerance and promote the use of the currently unexploited biotechnological potential of fungi that live in hypersaline environments.
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20
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Jaag HM, Nagy PD. The combined effect of environmental and host factors on the emergence of viral RNA recombinants. PLoS Pathog 2010; 6:e1001156. [PMID: 20975943 PMCID: PMC2958810 DOI: 10.1371/journal.ppat.1001156] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2010] [Accepted: 09/20/2010] [Indexed: 12/31/2022] Open
Abstract
Viruses are masters of evolution due to high frequency mutations and genetic recombination. In spite of the significance of viral RNA recombination that promotes the emergence of drug-resistant virus strains, the role of host and environmental factors in RNA recombination is poorly understood. Here we report that the host Met22p/Hal2p bisphosphate-3'-nucleotidase regulates the frequency of viral RNA recombination and the efficiency of viral replication. Based on Tomato bushy stunt virus (TBSV) and yeast as a model host, we demonstrate that deletion of MET22 in yeast or knockdown of AHL, SAL1 and FRY1 nucleotidases/phosphatases in plants leads to increased TBSV recombination and replication. Using a cell-free TBSV recombination/replication assay, we show that the substrate of the above nucleotidases, namely 3'-phosphoadenosine-5'-phosphate pAp, inhibits the activity of the Xrn1p 5'-3' ribonuclease, a known suppressor of TBSV recombination. Inhibition of the activity of the nucleotidases by LiCl and NaCl also leads to increased TBSV recombination, demonstrating that environmental factors could also affect viral RNA recombination. Thus, host factors in combination with environmental factors likely affect virus evolution and adaptation.
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MESH Headings
- Environment
- Evolution, Molecular
- Host-Pathogen Interactions/genetics
- Host-Pathogen Interactions/physiology
- Models, Biological
- Nucleotidases/genetics
- Nucleotidases/metabolism
- Nucleotidases/physiology
- Organisms, Genetically Modified
- RNA/genetics
- RNA/metabolism
- RNA Splicing/physiology
- RNA, Viral/genetics
- RNA, Viral/metabolism
- Recombination, Genetic/drug effects
- Recombination, Genetic/physiology
- Saccharomyces cerevisiae/drug effects
- Saccharomyces cerevisiae/genetics
- Saccharomyces cerevisiae/metabolism
- Saccharomyces cerevisiae/virology
- Salts/pharmacology
- Stress, Physiological/drug effects
- Stress, Physiological/genetics
- Stress, Physiological/physiology
- Nicotiana/drug effects
- Nicotiana/genetics
- Nicotiana/metabolism
- Tombusvirus/genetics
- Tombusvirus/physiology
- Virus Replication/genetics
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Affiliation(s)
- Hannah M. Jaag
- Department of Plant Pathology, University of Kentucky, Plant Science Building, Lexington, Kentucky, United States of America
| | - Peter D. Nagy
- Department of Plant Pathology, University of Kentucky, Plant Science Building, Lexington, Kentucky, United States of America
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21
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Lu SY, Zhao GR, Wu AM, Jenks MA, Zhang S, Liu JY. Molecular cloning of a cotton phosphatase gene and its functional characterization. BIOCHEMISTRY (MOSCOW) 2010; 75:85-94. [DOI: 10.1134/s0006297910010116] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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22
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Li Z, Stieglitz KA, Shrout AL, Wei Y, Weis RM, Stec B, Roberts MF. Mobile loop mutations in an archaeal inositol monophosphatase: modulating three-metal ion assisted catalysis and lithium inhibition. Protein Sci 2010; 19:309-18. [PMID: 20027624 PMCID: PMC2865715 DOI: 10.1002/pro.315] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2009] [Revised: 11/20/2009] [Accepted: 12/10/2009] [Indexed: 01/20/2023]
Abstract
The inositol monophosphatase (IMPase) enzyme from the hyperthermophilic archaeon Methanocaldococcus jannaschii requires Mg(2+) for activity and binds three to four ions tightly in the absence of ligands: K(D) = 0.8 muM for one ion with a K(D) of 38 muM for the other Mg(2+) ions. However, the enzyme requires 5-10 mM Mg(2+) for optimum catalysis, suggesting substrate alters the metal ion affinity. In crystal structures of this archaeal IMPase with products, one of the three metal ions is coordinated by only one protein contact, Asp38. The importance of this and three other acidic residues in a mobile loop that approaches the active site was probed with mutational studies. Only D38A exhibited an increased kinetic K(D) for Mg(2+); D26A, E39A, and E41A showed no significant change in the Mg(2+) requirement for optimal activity. D38A also showed an increased K(m), but little effect on k(cat). This behavior is consistent with this side chain coordinating the third metal ion in the substrate complex, but with sufficient flexibility in the loop such that other acidic residues could position the Mg(2+) in the active site in the absence of Asp38. While lithium ion inhibition of the archaeal IMPase is very poor (IC(50) approximately 250 mM), the D38A enzyme has a dramatically enhanced sensitivity to Li(+) with an IC(50) of 12 mM. These results constitute additional evidence for three metal ion assisted catalysis with substrate and product binding reducing affinity of the third necessary metal ion. They also suggest a specific mode of action for lithium inhibition in the IMPase superfamily.
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Affiliation(s)
- Zheng Li
- Department of Chemistry, Boston CollegeChestnut Hill, Massachusetts 02467
| | - Kimberly A Stieglitz
- Science, Technology, Engineering, and Mathematics, Roxbury Community CollegeBoston, Massachusetts 02120
| | - Anthony L Shrout
- Department of Chemistry, University of MassachusettsAmherst, Massachusetts 01003
| | - Yang Wei
- Department of Chemistry, Boston CollegeChestnut Hill, Massachusetts 02467
| | - Robert M Weis
- Department of Chemistry, University of MassachusettsAmherst, Massachusetts 01003
| | - Boguslaw Stec
- The Burnham Institute for Medical ResearchLa Jolla, California 92037
| | - Mary F Roberts
- Department of Chemistry, Boston CollegeChestnut Hill, Massachusetts 02467
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23
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Brown G, Singer A, Lunin VV, Proudfoot M, Skarina T, Flick R, Kochinyan S, Sanishvili R, Joachimiak A, Edwards AM, Savchenko A, Yakunin AF. Structural and biochemical characterization of the type II fructose-1,6-bisphosphatase GlpX from Escherichia coli. J Biol Chem 2009; 284:3784-92. [PMID: 19073594 PMCID: PMC2635049 DOI: 10.1074/jbc.m808186200] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2008] [Revised: 12/08/2008] [Indexed: 11/06/2022] Open
Abstract
Gluconeogenesis is an important metabolic pathway, which produces glucose from noncarbohydrate precursors such as organic acids, fatty acids, amino acids, or glycerol. Fructose-1,6-bisphosphatase, a key enzyme of gluconeogenesis, is found in all organisms, and five different classes of these enzymes have been identified. Here we demonstrate that Escherichia coli has two class II fructose-1,6-bisphosphatases, GlpX and YggF, which show different catalytic properties. We present the first crystal structure of a class II fructose-1,6-bisphosphatase (GlpX) determined in a free state and in the complex with a substrate (fructose 1,6-bisphosphate) or inhibitor (phosphate). The crystal structure of the ligand-free GlpX revealed a compact, globular shape with two alpha/beta-sandwich domains. The core fold of GlpX is structurally similar to that of Li+-sensitive phosphatases implying that they have a common evolutionary origin and catalytic mechanism. The structure of the GlpX complex with fructose 1,6-bisphosphate revealed that the active site is located between two domains and accommodates several conserved residues coordinating two metal ions and the substrate. The third metal ion is bound to phosphate 6 of the substrate. Inorganic phosphate strongly inhibited activity of both GlpX and YggF, and the crystal structure of the GlpX complex with phosphate demonstrated that the inhibitor molecule binds to the active site. Alanine replacement mutagenesis of GlpX identified 12 conserved residues important for activity and suggested that Thr(90) is the primary catalytic residue. Our data provide insight into the molecular mechanisms of the substrate specificity and catalysis of GlpX and other class II fructose-1,6-bisphosphatases.
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Affiliation(s)
- Greg Brown
- Banting and Best Department of Medical Research, University of Toronto, Toronto, Ontario M5G 1L6, Canada
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24
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Brucet M, Querol-Audí J, Bertlik K, Lloberas J, Fita I, Celada A. Structural and biochemical studies of TREX1 inhibition by metals. Identification of a new active histidine conserved in DEDDh exonucleases. Protein Sci 2008; 17:2059-69. [PMID: 18780819 DOI: 10.1110/ps.036426.108] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
TREX1 is the major exonuclease in mammalian cells, exhibiting the highest level of activity with a 3'-->5' activity. This exonuclease is responsible in humans for Aicardi-Goutières syndrome and for an autosomal dominant retinal vasculopathy with cerebral leukodystrophy. In addition, this enzyme is associated with systemic lupus erythematosus. TREX1 belongs to the exonuclease DEDDh family, whose members display low levels of sequence identity, while possessing a common fold and active site organization. For these exonucleases, a catalytic mechanism has been proposed that involves two divalent metal ions bound to the DEDD motif. Here we studied the interaction of TREX1 with the monovalent cations lithium and sodium. We demonstrate that these metals inhibit the exonucleolytic activity of TREX1, as measured by the classical gel method, as well as by a new technique developed for monitoring the real-time exonuclease reaction. The X-ray structures of the enzyme in complex with these two cations and with a nucleotide, a product of the exonuclease reaction, were determined at 2.1 A and 2.3 A, respectively. A comparison with the structures of the active complexes (in the presence of magnesium or manganese) explains that the inhibition mechanism is caused by the noncatalytic metals competing with distinct affinities for the two metal-binding sites and inducing subtle rearrangements in active centers. Our analysis also reveals that a histidine residue (His124), highly conserved in the DEDDh family, is involved in the activity of TREX1, as confirmed by mutational studies. Our results shed further light on the mechanism of activity of the DEDEh family of exonucleases.
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Affiliation(s)
- Marina Brucet
- Macrophage Biology Group, Institute for Research in Biomedicine and University of Barcelona, Barcelona Science Park, 08028 Barcelona, Spain
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25
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Abstract
This overview provides an illustrated, comprehensive survey of some commonly observed protein‐fold families and structural motifs, chosen for their functional significance. It opens with descriptions and definitions of the various elements of protein structure and associated terminology. Following is an introduction into web‐based structural bioinformatics that includes surveys of interactive web servers for protein fold or domain annotation, protein‐structure databases, protein‐structure‐classification databases, structural alignments of proteins, and molecular graphics programs available for personal computers. The rest of the overview describes selected families of protein folds in terms of their secondary, tertiary, and quaternary structural arrangements, including ribbon‐diagram examples, tables of representative structures with references, and brief explanations pointing out their respective biological and functional significance.
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Affiliation(s)
- Peter D Sun
- National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, USA
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26
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Hatzios SK, Iavarone AT, Bertozzi CR. Rv2131c from Mycobacterium tuberculosis is a CysQ 3'-phosphoadenosine-5'-phosphatase. Biochemistry 2008; 47:5823-31. [PMID: 18454554 PMCID: PMC2711008 DOI: 10.1021/bi702453s] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
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Mycobacterium tuberculosis (Mtb) produces a number of sulfur-containing metabolites that contribute to its pathogenesis and ability to survive in the host. These metabolites are products of the sulfate assimilation pathway. CysQ, a 3′-phosphoadenosine-5′-phosphatase, is considered an important regulator of this pathway in plants, yeast, and other bacteria. By controlling the pools of 3′-phosphoadenosine 5′-phosphate (PAP) and 3′-phosphoadenosine 5′-phosphosulfate (PAPS), CysQ has the potential to modulate flux in the biosynthesis of essential sulfur-containing metabolites. Bioinformatic analysis of the Mtb genome suggests the presence of a CysQ homologue encoded by the gene Rv2131c. However, a recent biochemical study assigned the protein’s function as a class IV fructose-1,6-bisphosphatase. In the present study, we expressed Rv2131c heterologously and found that the protein dephosphorylates PAP in a magnesium-dependent manner, with optimal activity observed between pH 8.5 and pH 9.5 using 0.5 mM MgCl2. A sensitive electrospray ionization mass spectrometry-based assay was used to extract the kinetic parameters for PAP, revealing a Km (8.1 ± 3.1 μM) and kcat (5.4 ± 1.1 s−1) comparable to those reported for other CysQ enzymes. The second-order rate constant for PAP was determined to be over 3 orders of magnitude greater than those determined for myo-inositol 1-phosphate (IMP) and fructose 1,6-bisphosphate (FBP), previously considered to be the primary substrates of this enzyme. Moreover, the ability of the Rv2131c-encoded enzyme to dephosphorylate PAP and PAPS in vivo was confirmed by functional complementation of an Escherichia coli ΔcysQ mutant. Taken together, these studies indicate that Rv2131c encodes a CysQ enzyme that may play a role in mycobacterial sulfur metabolism.
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Affiliation(s)
- Stavroula K Hatzios
- Department of Chemistry, University of California, Berkeley, California 94720, USA
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27
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Creation of salt-insensitive 3′(2′),5′-bisphosphate nucleotidase by modeling and mutagenesis approach. Arch Biochem Biophys 2008; 469:174-83. [DOI: 10.1016/j.abb.2007.10.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2007] [Revised: 10/17/2007] [Accepted: 10/19/2007] [Indexed: 01/11/2023]
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28
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Brown AK, Meng G, Ghadbane H, Scott DJ, Dover LG, Nigou J, Besra GS, Fütterer K. Dimerization of inositol monophosphatase Mycobacterium tuberculosis SuhB is not constitutive, but induced by binding of the activator Mg2+. BMC STRUCTURAL BIOLOGY 2007; 7:55. [PMID: 17725819 PMCID: PMC2080633 DOI: 10.1186/1472-6807-7-55] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/22/2007] [Accepted: 08/28/2007] [Indexed: 12/21/2022]
Abstract
BACKGROUND The cell wall of Mycobacterium tuberculosis contains a wide range of phosphatidyl inositol-based glycolipids that play critical structural roles and, in part, govern pathogen-host interactions. Synthesis of phosphatidyl inositol is dependent on free myo-inositol, generated through dephosphorylation of myo-inositol-1-phosphate by inositol monophosphatase (IMPase). Human IMPase, the putative target of lithium therapy, has been studied extensively, but the function of four IMPase-like genes in M. tuberculosis is unclear. RESULTS We determined the crystal structure, to 2.6 A resolution, of the IMPase M. tuberculosis SuhB in the apo form, and analysed self-assembly by analytical ultracentrifugation. Contrary to the paradigm of constitutive dimerization of IMPases, SuhB is predominantly monomeric in the absence of the physiological activator Mg2+, in spite of a conserved fold and apparent dimerization in the crystal. However, Mg2+ concentrations that result in enzymatic activation of SuhB decisively promote dimerization, with the inhibitor Li+ amplifying the effect of Mg2+, but failing to induce dimerization on its own. CONCLUSION The correlation of Mg2+-driven enzymatic activity with dimerization suggests that catalytic activity is linked to the dimer form. Current models of lithium inhibition of IMPases posit that Li+ competes for one of three catalytic Mg2+ sites in the active site, stabilized by a mobile loop at the dimer interface. Our data suggest that Mg2+/Li+-induced ordering of this loop may promote dimerization by expanding the dimer interface of SuhB. The dynamic nature of the monomer-dimer equilibrium may also explain the extended concentration range over which Mg2+ maintains SuhB activity.
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Affiliation(s)
- Alistair K Brown
- School of Biosciences, The University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Guoyu Meng
- School of Biosciences, The University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
- Present address : School of Crystallography, Birkbeck College, Malet Street, London WC1E 7HX, UK
| | - Hemza Ghadbane
- School of Biosciences, The University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - David J Scott
- National Centre for Macromolecular Hydrodynamics, School of Biosciences, University of Nottingham, Sutton Bonington, LE12 5RD, UK
| | - Lynn G Dover
- School of Biosciences, The University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Jérôme Nigou
- Department of Molecular Mechanisms of Mycobacterial Infections, Institut de Pharmacologie et de Biologie Structurale, Centre National de la Recherche Scientifique Unité Mixte de Recherche 5089, Toulouse, France
| | - Gurdyal S Besra
- School of Biosciences, The University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Klaus Fütterer
- School of Biosciences, The University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
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29
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Lu ZJ, Markham GD. Metal Ion Activation of S-Adenosylmethionine Decarboxylase Reflects Cation Charge Density. Biochemistry 2007; 46:8172-80. [PMID: 17567041 DOI: 10.1021/bi6025962] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
S-Adenosylmethionine decarboxylase from Escherichia coli is a pyruvoyl cofactor-containing enzyme that requires a metal cation for activity. We have found that the enzyme is activated by cations of varying charge and ionic radius, such as Li+, A13+, Tb3+, and Eu3+, as well as the divalent cations Mg2+, Mn2+, and Ca2+. All of the activating cations provide kcat values within 30-fold of one another, showing that the charge of the cation does not greatly influence the rate-limiting step for decarboxylase turnover. Cation concentrations for half-maximal activation decrease by >100-fold with each increment of increase in the cation charge, ranging from approximately 300 mM with Li+ to approximately 2 microM with trivalent lanthanide ions. The cation affinity is related to the charge/radius ratio of the ion for those ions with exchangeable first coordination sphere ligands. The exchange-inert cation Co(NH3)63+ activates in the presence of excess EDTA (and NH4+ does not activate), indicating that direct metal coordination to the protein or substrate is not required for activation. The binding of metal ions (monitored by changes in the protein tryptophan fluorescence) and enzyme activation are both cooperative with Hill coefficients as large as 4, the active site stoichiometry of this (alphabeta)4 enzyme. The Hill coefficients for Mg2+ binding and activation increase from 1 to approximately 4 as the KCl concentration increases, which is also observed with NaCl or KNO3; neither Na+ nor K+ activates the enzyme. The single tryptophan in the protein is located 16 residues from the carboxyl terminus of the pyruvoyl-containing alpha chain, in a 70-residue segment that is not present in metal ion independent AdoMet decarboxylases from other organisms. The results are consistent with allosteric metal ion activation of the enzyme, congruent with the role of the putrescine activator of the mammalian AdoMet decarboxylase.
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Affiliation(s)
- Zichun J Lu
- Institute for Cancer Research, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, Pennsylvania 19111, USA
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30
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Cheong JJ, Hwang I, Rhee S, Moon TW, Choi YD, Kwon HB. Complementation of an E. coli cysteine auxotrophic mutant for the structural modification study of 3′(2′),5′-bisphosphate nucleotidase. Biotechnol Lett 2007; 29:913-8. [PMID: 17450323 DOI: 10.1007/s10529-007-9324-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2006] [Revised: 01/04/2007] [Accepted: 01/05/2007] [Indexed: 11/27/2022]
Abstract
The Arabidopsis AHL gene encodes a 3'(2'),5'-bisphosphate nucleotidase (BPNTase) involved in the reductive sulfate activation pathway. A bacterial expression vector containing AHL cDNA was randomly mutagenized with hydroxylamine and transformed into the E. coli cysteine auxotrophic mutant cysQ. Bacterial colonies that did not show evidence of complementation, i.e. those that exhibited slower growth on cysteine-free medium, were selected for further study. Sequencing of the AHL cDNA in one such clone revealed the conversion of cytosine 635 (C635) to thymine, resulting in an Alanine (A212) to Valine substitution. This microbial complementation procedure is useful in BPNTase structure-activity studies for biotechnological applications.
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Affiliation(s)
- Jong-Joo Cheong
- School of Agricultural Biotechnology and Center for Agricultural Biomaterials, Seoul National University, Seoul, Korea.
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31
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Aggarwal M, Mondal AK. Role of N-terminal hydrophobic region in modulating the subcellular localization and enzyme activity of the bisphosphate nucleotidase from Debaryomyces hansenii. EUKARYOTIC CELL 2006; 5:262-71. [PMID: 16467467 PMCID: PMC1405886 DOI: 10.1128/ec.5.2.262-271.2006] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
3', 5'-Bisphosphate nucleotidase is a ubiquitous enzyme that converts 3'-phosphoadenosine-5'-phosphate to adenosine-5'-phosphate and inorganic phosphate. These enzymes are highly sensitive to sodium and lithium and, thus, perform a crucial rate-limiting metabolic step during salt stress in yeast. Recently, we have identified a bisphosphate nucleotidase gene (DHAL2) from the halotolerant yeast Debaryomyces hansenii. One of the unique features of Dhal2p is that it contains an N-terminal 54-amino-acid-residue hydrophobic extension. In this study, we have shown that Dhal2p exists as a cytosolic as well as a membrane-bound form and that salt stress markedly influences the accumulation of the latter form in the cell. We have demonstrated that the N-terminal hydrophobic region was necessary for the synthesis of the membrane-bound isoform. It appeared that an alternative translation initiation was the major mechanism for the synthesis of these two forms. Moreover, the two forms exhibit significant differences in their substrate specificity. Unlike the cytosolic form, the membrane-bound form showed very high activity against inositol-1,4-bisphosphate. Thus, the present study for the first time reports the existence of multiple forms of a bisphosphate nucleotidase in any organism.
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Affiliation(s)
- Monika Aggarwal
- Institute of Microbial Technology, Sector 39A, Chandigarh 160 036, India
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32
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Zhang JY, Zou J, Bao Q, Chen WL, Wang L, Yang H, Zhang CC. A lithium-sensitive and sodium-tolerant 3'-phosphoadenosine-5'-phosphatase encoded by halA from the cyanobacterium Arthrospira platensis is closely related to its counterparts from yeasts and plants. Appl Environ Microbiol 2006; 72:245-51. [PMID: 16391050 PMCID: PMC1352299 DOI: 10.1128/aem.72.1.245-251.2006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
3'-Phosphoadenosine-5'-phosphatase (PAPase) is required for the removal of toxic 3'-phosphoadenosine-5'-phosphate (PAP) produced during sulfur assimilation in various eukaryotic organisms. This enzyme is a well-known target of lithium and sodium toxicity and has been used for the production of salt-resistant transgenic plants. In addition, PAPase has also been proposed as a target in the treatment of manic-depressive patients. One gene, halA, which could encode a protein closely related to the PAPases of yeasts and plants, was identified from the cyanobacterium Arthrospira (Spirulina) platensis. Phylogenic analysis indicated that proteins related to PAPases from several cyanobacteria were found in different clades, suggesting multiple origins of PAPases in cyanobacteria. The HalA polypeptide from A. platensis was overproduced in Escherichia coli and used for the characterization of its biochemical properties. HalA was dependent on Mg2+ for its activity and could use PAP or 3'-phosphoadenosine-5'-phosphosulfate as a substrate. HalA is sensitive to Li+ (50% inhibitory concentration [IC50] = 3.6 mM) but only slightly sensitive to Na+ (IC50 = 600 mM). The salt sensitivity of HalA was thus different from that of most of its eukaryotic counterparts, which are much more sensitive to both Li+ and Na+, but was comparable to the PAPase AtAHL (Hal2p-like protein) from Arabidopsis thaliana. The properties of HalA could help us to understand the structure-function relationship underlying the salt sensitivity of PAPases. The expression of halA improved the Li+ tolerance of E. coli, suggesting that the sulfur-assimilating pathway is a likely target of salt toxicity in bacteria as well.
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Affiliation(s)
- Ju-Yuan Zhang
- National Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, People's Republic of China
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33
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Todeschini AL, Condon C, Bénard L. Sodium-induced GCN4 expression controls the accumulation of the 5' to 3' RNA degradation inhibitor, 3'-phosphoadenosine 5'-phosphate. J Biol Chem 2006; 281:3276-82. [PMID: 16352596 DOI: 10.1074/jbc.m511688200] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Most cytoplasmic mRNAs are decapped and digested by the 5'-3'-exonuclease Xrn1p in Saccharomyces cerevisiae. The activity of Xrn1p is naturally inhibited in the presence of 3'-phosphoadenosine 5'-phosphate (pAp), a metabolite produced during sulfate assimilation that is quickly metabolized to AMP by the enzymatic activity of Hal2p. However, pAp accumulates and 5'-3' degradation decreases in the presence of ions known to inhibit Hal2p activity, such as sodium or lithium. We have shown that yeast cells can better adapt to the presence of sodium than lithium because of their ability to reduce pAp accumulation by activating HAL2 expression in a Gcn4p-dependent response, a regulatory loop that is likely to be conserved in different yeast species. We have thus identified a new role for the transcriptional activity of Gcn4p in maintaining an active mRNA degradation pathway under conditions of sodium stress. Since deregulation of proteins involved in different metabolic pathways is observed in xrn1Delta mutants, the maintenance of mRNA degradation capacity is likely to be important for the accurate and rapid adaptation of gene expression to salt stress.
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34
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Gu X, Chen M, Shen H, Jiang X, Huang Y, Wang H. Rv2131c gene product: An unconventional enzyme that is both inositol monophosphatase and fructose-1,6-bisphosphatase. Biochem Biophys Res Commun 2006; 339:897-904. [PMID: 16325768 DOI: 10.1016/j.bbrc.2005.11.088] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2005] [Accepted: 11/16/2005] [Indexed: 11/20/2022]
Abstract
Inositol monophosphatase is an enzyme in the biosynthesis of myo-inostiol, a crucial substrate for the synthesis of phosphatidylinositol, which has been demonstrated to be an essential component of mycobacteria. In this study, the Rv2131c gene from Mycobacterium tuberculosis H37Rv was cloned into the pET28a vector and the recombinant plasmid was transformed into Escherichia coli BL21 (DE3) strain, allowing the expression of the enzyme in fusion with a histidine-rich peptide on the N-terminal. The fusion protein was purified from the soluble fraction of the lysed cells under native conditions by immobilized metal affinity chromatography (IMAC). The purified Rv2131c gene product showed inositol monophosphatase activity but with substrate specificity that was broader than those of several bacterial and eukaryotic inositol monophosphatases, and it also acted as fructose-1,6-bisphosphatase. The dimeric enzyme exhibited dual activities of IMPase and FBPase, with K(m) of 0.22+/-0.03mM for inositol-1-phosphate and K(m) of 0.45+/-0.05mM for fructose-1,6-bisphosphatase. To better understand the relationship between the function and structure of the Rv2131c enzyme, we constructed D40N, L71A, and D94N mutants and purified these corresponding proteins. Mutations of D40N and D94N caused the proteins to almost completely lose both the inositol monophosphatase and fructose-1,6-bisphosphatase activities. However, L71A mutant did not cause loss either of the activities, but the activity toward the inositol was 12-fold more resistant to inhibition by lithium (IC(50) approximately 60mM). Based on the substrate specificity and presence of conserved sequence motifs of the M. tuberculosis Rv2131c, we proposed that the enzyme belonged to class IV fructose-1,6-bisphosphatase (FBPase IV).
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Affiliation(s)
- Xiaoling Gu
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai 200433, PR China
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35
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Aggarwal M, Bansal PK, Mondal AK. Molecular cloning and biochemical characterization of a 3'(2'),5'-bisphosphate nucleotidase from Debaryomyces hansenii. Yeast 2005; 22:457-70. [PMID: 15849794 DOI: 10.1002/yea.1223] [Citation(s) in RCA: 20] [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
The enzyme 3'(2'),5'-bisphosphate nucleotidase catalyses a reaction that converts 3'-phosphoadenosine-5'-phosphate (PAP) to adenosine-5'-phosphate (AMP) and inorganic phosphate (Pi). The enzyme from Saccharomyces cerevisiae is highly sensitive to sodium and lithium and is thus considered to be the in vivo target of salt toxicity in yeast. In S. cerevisiae, the HAL2 gene encodes this enzyme. We have cloned a homologous gene, DHAL2, from the halotolerant yeast Debaryomyces hansenii. DNA sequencing of this clone revealed a 1260 bp open reading frame (ORF) that putatively encoded a protein of 420 amino acid residues. S. cerevisiae transformed with DHAL2 gene displayed higher halotolerance. Biochemical studies showed that recombinant Dhal2p could efficiently utilize PAP (K(m)17 microM) and PAPS (K(m)48 microM) as substrate. Moreover, we present evidence that, in comparison to other homologues from yeast, Dhal2p displays significantly higher resistance towards lithium and sodium ions.
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Affiliation(s)
- Monika Aggarwal
- Institute of Microbial Technology, Sector 39A, Chandigarh 160 036, India
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36
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Wang LY, Shimada K, Morishita M, Shiozaki K. Response of fission yeast to toxic cations involves cooperative action of the stress-activated protein kinase Spc1/Sty1 and the Hal4 protein kinase. Mol Cell Biol 2005; 25:3945-55. [PMID: 15870269 PMCID: PMC1087739 DOI: 10.1128/mcb.25.10.3945-3955.2005] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Stress-activated protein kinases (SAPKs), members of a mitogen-activated protein kinase (MAPK) subfamily, are highly conserved among eukaryotes. Studies of yeasts demonstrated that SAPKs play pivotal roles in survival responses to high osmolarity, oxidative stress, and heat shock. Here we report a novel physiological role of the fission yeast Spc1 SAPK in cellular resistance to certain cations, such as Na(+), Li(+), and Ca(2+). Strains lacking Spc1 or its activator, Wis1 MAPK kinase, are hypersensitive to these cations. Spc1 positively regulates expression of sod2(+) encoding a Na(+)/H(+) antiporter through Atf1 and other transcription factors. In addition, we have identified a novel Spc1-interacting protein, Hal4, which is highly homologous to the budding yeast Sat4/Hal4 protein kinase. Like its budding yeast counterpart, the fission yeast Hal4 kinase is essential for cellular resistance to Na(+), Li(+), and Ca(2+). The hal4-null phenotype is complemented by overexpression of the Trk1 potassium transporter or increased K(+) in the growth medium, suggesting that Hal4 promotes K(+) uptake, which consequently increases cellular resistance to other cations. Interestingly, the Spc1-Hal4 interaction appears to be required for cellular resistance to Ca(2+) but not Na(+) and Li(+). We propose that Spc1 SAPK and Hal4 kinase cooperatively function to protect cells from the toxic cations.
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Affiliation(s)
- Ling-Yu Wang
- Section of Microbiology, Division of Biological Sciences, University of California, Davis, CA 95616, USA
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37
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Shull NP, Spinelli SL, Phizicky EM. A highly specific phosphatase that acts on ADP-ribose 1''-phosphate, a metabolite of tRNA splicing in Saccharomyces cerevisiae. Nucleic Acids Res 2005; 33:650-60. [PMID: 15684411 PMCID: PMC548356 DOI: 10.1093/nar/gki211] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2004] [Revised: 01/07/2005] [Accepted: 01/07/2005] [Indexed: 11/21/2022] Open
Abstract
One molecule of ADP-ribose 1'',2''-cyclic phosphate (Appr>p) is formed during each of the approximately 500 000 tRNA splicing events per Saccharomyces cerevisiae generation. The metabolism of Appr>p remains poorly defined. A cyclic phosphodiesterase (Cpd1p) has been shown to convert Appr>p to ADP-ribose-1''-phosphate (Appr1p). We used a biochemical genomics approach to identify two yeast phosphatases that can convert Appr1p to ADP-ribose: the product of ORF YBR022w (now Poa1p), which is completely unrelated to other known phosphatases; and Hal2p, a known 3'-phosphatase of 5',3'-pAp. Poa1p is highly specific for Appr1p, and thus likely acts on this molecule in vivo. Poa1 has a relatively low K(M) for Appr1p (2.8 microM) and a modest kcat (1.7 min(-1)), but no detectable activity on several other substrates. Furthermore, Poa1p is strongly inhibited by ADP-ribose (K(I), 17 microM), modestly inhibited by other nucleotides containing an ADP-ribose moiety and not inhibited at all by other tested molecules. In contrast, Hal2p is much more active on pAp than on Appr1p, and several other tested molecules were Hal2p substrates or inhibitors. poa1-Delta mutants have no obvious growth defect at different temperatures in rich media, and analysis of yeast extracts suggests that approximately 90% of Appr1p processing activity originates from Poa1p.
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Affiliation(s)
- Neil P. Shull
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine601 Elmwood Avenue, Rochester, NY 14642, USA
| | - Sherry L. Spinelli
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine601 Elmwood Avenue, Rochester, NY 14642, USA
| | - Eric M. Phizicky
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine601 Elmwood Avenue, Rochester, NY 14642, USA
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38
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Li Z, Zhao L, Kai G, Yu S, Cao Y, Pang Y, Sun X, Tang K. Cloning and expression analysis of a water stress-induced gene from Brassica oleracea. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2004; 42:789-94. [PMID: 15596098 DOI: 10.1016/j.plaphy.2004.09.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2004] [Accepted: 09/07/2004] [Indexed: 05/01/2023]
Abstract
Plant growth and productivity are greatly affected by water stress, such as drought and salinity. Here we report on the cloning and expression analysis of a water stress-induced gene from Brassica oleracea (designated as BoWS, GenBank accession number AY571333) by rapid amplification of cDNA ends (RACE). The full-length cDNA of BoWS consisted of 594 bp and contained a 285 bp open reading frame (ORF) encoding a 95-amino-acid protein. The deduced protein had a calculated molecular mass of 10.53 kDa and an isoelectric point of 6.93. The sequence similarity and comparative analysis showed that BoWS was 84% identical to Arabidopsis thaliana putative water stress-induced protein (GenBank accession number AAM67282). Southern blot analysis indicated that BoWS was a low-copy gene. Northern blot analysis revealed that the expression of BoWS was upregulated by abscisic acid (ABA), mannitol, NaCl, drought, salicylic acid (SA) and hydrogen peroxide (H(2)O(2)). Our results indicate that BoWS is extremely related to the water-deficit stress in B. oleracea.
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Affiliation(s)
- Zhugang Li
- Plant Biotechnology Research Center, Fudan-SJTU-Nottingham Plant Biotechnology R&D Center, School of Agriculture and Biology, Shanghai Jiaotong University, 1954 Huashan Road, Shanghai 200030, China
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39
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Xiong L, Lee H, Huang R, Zhu JK. A single amino acid substitution in the Arabidopsis FIERY1/HOS2 protein confers cold signaling specificity and lithium tolerance. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2004; 40:536-545. [PMID: 15500469 DOI: 10.1111/j.1365-313x.2004.02225.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Low temperature induces the expression of many plant genes through undefined signaling pathways. To gain insight into cold signal transduction mechanisms, we isolated Arabidopsis mutants that exhibited altered regulation of low temperature-induced gene expression. One such mutant, hos2, was shown previously to have an enhanced induction of stress-responsive genes by cold, whereas the expression of these genes under osmotic stress or the phytohormone absciscic acid (ABA) treatments was not affected. Here we further define the targets of HOS2 by examining the regulation of upstream cold-specific CBF transcription factor genes. It was found that the transcript levels of CBF2 and CBF3 were significantly higher in hos2 mutant plants than in the wild type under cold treatments, suggesting that HOS2 may act upstream of CBFs. The HOS2 gene was cloned using a map-based strategy. Surprisingly, HOS2 is identical to the FIERY1 gene that we had described previously. FIERY1 is a general negative regulator that controls cold, osmotic stress, and ABA signal transduction and possesses inositol polyphosphate 1-phosphatase activity. The hos2 mutation rendered the HOS2/FIERY1 recombinant protein completely inactive in the cold but did not substantially affect its activity at warm temperatures. Interestingly, the hos2 mutant protein is extremely tolerant to Li+. This study provides a unique example of a single amino acid substitution in a critical regulator that can lead to conditional changes in protein functions and distinct plant phenotypes. The results reinforce the notion that phosphoinositols are important second messengers in cold signal transduction, and shed light on how the diversity of plant tolerance to cold and other abiotic stresses may evolve due to variations in a common molecular switch.
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Affiliation(s)
- Liming Xiong
- Department of Plant Sciences, University of Arizona, Tucson, AZ 85721, USA
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40
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Gutteridge A, Thornton J. Conformational change in substrate binding, catalysis and product release: an open and shut case? FEBS Lett 2004; 567:67-73. [PMID: 15165895 DOI: 10.1016/j.febslet.2004.03.067] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2004] [Revised: 03/01/2004] [Accepted: 03/07/2004] [Indexed: 11/18/2022]
Abstract
The role of conformational change in substrate binding, catalysis and product release is reviewed for 11 enzymes, for which crystal structures are available for the apo, substrate- and product-bound states. The extent of global conformational changes is measured, and the movements of the functional regions involved in catalysis and ligand binding are compared to the rest of the structure. We find that most of these enzymes undergo relatively small amounts of conformational change and particularly small changes in catalytic residue geometry, usually less than 1 A. In some enzymes there is significant movement of the binding residues, usually on surface loops.
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Affiliation(s)
- Alex Gutteridge
- EBI, Wellcome Trust Genome Campus, Hinxton, Cambridgeshire CB10 1SD, UK.
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41
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Forment J, Mulet JM, Vicente O, Serrano R. The yeast SR protein kinase Sky1p modulates salt tolerance, membrane potential and the Trk1,2 potassium transporter. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1565:36-40. [PMID: 12225850 DOI: 10.1016/s0005-2736(02)00503-5] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Protein kinases dedicated to the phosphorylation of SR proteins have been implicated in the processing and nuclear export of mRNAs. Here we demonstrate in Saccharomyces cerevisiae their participation in cation homeostasis. A null mutant of the single yeast SR protein kinase Sky1p is viable but exhibits increased tolerance to diverse toxic cations such as Na(+), Li(+), spermine, tetramethylammonium, hygromycin B and Mn(2+). This pleiotropic phenotype correlates with reduced accumulation of cations, suggesting a decrease in membrane electrical potential. Genetic analysis and Rb(+) uptake measurements indicate that Sky1p modulates Trk1,2, the high-affinity K(+) uptake system of yeast and a major determinant of membrane potential.
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Affiliation(s)
- Javier Forment
- Dept. de Biotecnologia, Instituto de Biologi;a Molecular y Celular de Plantas, Universidad Politécnica de Valencia-CSIC, Avenida de los Naranjos s/n, Camino de Vera, 46022, Valencia, Spain
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42
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Patel S, Martínez-Ripoll M, Blundell TL, Albert A. Structural enzymology of Li(+)-sensitive/Mg(2+)-dependent phosphatases. J Mol Biol 2002; 320:1087-94. [PMID: 12126627 DOI: 10.1016/s0022-2836(02)00564-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Li(+)-sensitive/Mg(2+)-dependent phosphatases have attracted considerable attention since they have been proposed as targets for lithium therapy in the treatment of manic-depressive patients. The members of this enzyme superfamily display low levels of sequence identity while possessing a common fold and active site. Extensive structural and biochemical data demonstrate the direct involvement of two metal ions in catalysis, and show that lithium exerts its inhibitory action by blocking the products at the active site. By exploiting the different inhibitory properties of magnesium and calcium, we have been able to solve the X-ray structures of the Li(+)-sensitive/Mg(2+)-dependent 3'-phosphoadenosine-5'-phosphatase in complex with its substrate and with its products. The structural comparison of these complexes provides a 3D picture of the different stages of the catalytic cycle. This gives new insights into the understanding of the biological function of this group of enzymes and their lithium inhibition, and should assist in the design of improved inhibitors of therapeutic value.
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Affiliation(s)
- S Patel
- Department of Biochemistry, University of Cambridge, Cambridge, UK
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Stieglitz KA, Johnson KA, Yang H, Roberts MF, Seaton BA, Head JF, Stec B. Crystal structure of a dual activity IMPase/FBPase (AF2372) from Archaeoglobus fulgidus. The story of a mobile loop. J Biol Chem 2002; 277:22863-74. [PMID: 11940584 DOI: 10.1074/jbc.m201042200] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Several hyperthermophilic organisms contain an unusual phosphatase that has dual activity toward inositol monophosphates and fructose 1,6-bisphosphate. The structure of the second member of this family, an FBPase/IMPase from Archaeoglobus fulgidus (AF2372), has been solved. This enzyme shares many kinetic and structural similarities with that of a previously solved enzyme from Methanococcus jannaschii (MJ0109). It also shows some kinetic differences in divalent metal ion binding as well as structural variations at the dimer interface that correlate with decreased thermal stability. The availability of different crystal forms allowed us to investigate the effect of the presence of ligands on the conformation of a mobile catalytic loop independently of the crystal packing. This conformational variability in AF2372 is compared with that observed in other members of this structural family that are sensitive or insensitive to submillimolar concentrations of Li(+). This analysis provides support for the previously proposed mechanism of catalysis involving three metal ions. A direct correlation of the loop conformation with strength of Li(+) inhibition provides a useful system of classification for this extended family of enzymes.
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Affiliation(s)
- Kimberly A Stieglitz
- Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, USA
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Nigou J, Dover LG, Besra GS. Purification and biochemical characterization of Mycobacterium tuberculosis SuhB, an inositol monophosphatase involved in inositol biosynthesis. Biochemistry 2002; 41:4392-8. [PMID: 11914086 DOI: 10.1021/bi0160056] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Phosphatidylinositol is an essential component of mycobacteria, and phosphatidylinositol-based lipids such as phosphatidylinositolmannosides, lipomannan, and lipoarabinomannan are major immunomodulatory components of the Mycobacterium tuberculosis cell wall. Inositol monophosphatase (EC 3.1.3.25) is a crucial enzyme in the biosynthesis of free myo-inositol from inositol-1-phosphate, a key substrate for the phosphatidylinositol synthase in mycobacteria. Analysis of the M. tuberculosis genome suggested the presence of four M. tuberculosis gene products that exhibit an inositol monophosphatase signature. In the present report, we have focused on SuhB, which possesses the highest degree of homology with human inositol monophosphatase. SuhB gene was cloned into an E. coli expression vector to over-produce a His-tagged protein, which was purified and characterized. SuhB required divalent metal ions for functional inositol monophosphatase activity, with Mg(2+) being the strongest activator. Inositol monophosphatase activity catalyzed by SuhB was inhibited by the monovalent cation lithium (IC(50) = 0.9 mM). As anticipated, inositol-1-phosphate was the preferred substrate (K(m) = 0.177 +/- 0.025 mM; k(cat) = 3.6 +/- 0.2 s(-)(1)); however, SuhB was also able to hydrolyze a variety of polyol phosphates such as glucitol-6-phosphate, glycerol-2-phosphate, and 2'-AMP. To provide further insight into the structure-function relationship of SuhB, different mutant proteins were generated (E83D, D104N, D107N, W234L, and D235N). These mutations almost completely abrogated inositol monophosphatase activity, thus underlining the importance of these residues in inositol-1-phosphate dephosphorylation. We also identified L81 as a key residue involved in sensitivity to lithium. The L81A mutation rendered SuhB inositol monophosphatase activity 10-fold more resistant to inhibition by lithium (IC(50) = 10 mM). These studies provide the first steps in the delineation of the biosynthesis of the key metabolite inositol in M. tuberculosis.
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Affiliation(s)
- Jérôme Nigou
- Department of Microbiology and Immunology, The University of Newcastle upon Tyne, The Medical School, Framlington Place, Newcastle upon Tyne, NE2 4HH, U.K
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Yenush L, Mulet JM, Ariño J, Serrano R. The Ppz protein phosphatases are key regulators of K+ and pH homeostasis: implications for salt tolerance, cell wall integrity and cell cycle progression. EMBO J 2002; 21:920-9. [PMID: 11867520 PMCID: PMC125902 DOI: 10.1093/emboj/21.5.920] [Citation(s) in RCA: 121] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The yeast Ppz protein phosphatases and the Hal3p inhibitory subunit are important determinants of salt tolerance, cell wall integrity and cell cycle progression. We present several lines of evidence showing that these disparate phenotypes are connected by the fact that Ppz regulates K+ transport. First, salt tolerance, cell wall integrity and cell cycle phenotypes of Ppz mutants are dependent on the Trk K+ transporters. Secondly, Ppz mutants exhibit altered activity of the Trk system, as measured by rubidium uptake. Thirdly, Ppz mutants exhibit altered intracellular K+ and pH, as expected from H+ efflux providing electrical balance during K+ uptake. Our unifying picture of Ppz phenotypes contends that activation of Trk by decreased Ppz activity results in plasma membrane depolarization (reducing uptake of toxic cations), increased intracellular K+ and turgor (compromising cell integrity), and increased intracellular pH (augmenting the expression of pH-regulated genes and facilitating alpha-factor recovery). In addition to providing a coherent explanation for all Ppz-dependent phenotypes, our results provide evidence for a causal relationship between intracellular cation homeostasis and a potential cell cycle checkpoint.
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Affiliation(s)
| | | | - Joaquín Ariño
- Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-CSIC, Camino de Vera s/n, E-46022 Valencia and
Departament de Bioquímica i Biologia Molecular, Fac. Veterinària, Universitat Autònoma de Barcelona, Bellaterra 08193, Barcelona, Spain Corresponding author e-mail:
| | - Ramón Serrano
- Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-CSIC, Camino de Vera s/n, E-46022 Valencia and
Departament de Bioquímica i Biologia Molecular, Fac. Veterinària, Universitat Autònoma de Barcelona, Bellaterra 08193, Barcelona, Spain Corresponding author e-mail:
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Patel S, Yenush L, Rodríguez PL, Serrano R, Blundell TL. Crystal structure of an enzyme displaying both inositol-polyphosphate-1-phosphatase and 3'-phosphoadenosine-5'-phosphate phosphatase activities: a novel target of lithium therapy. J Mol Biol 2002; 315:677-85. [PMID: 11812139 DOI: 10.1006/jmbi.2001.5271] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Lithium cations exert profound and selective psychopharmacological effects on ameliorate manic-depressive psychosis. Although lithium is an effective drug for both treatment and prophylaxis of bipolar disorder, the precise mechanism of action is not well understood. Lithium acts as both an uncompetitive and non-competitive inhibitor of several lithium- sensitive phosphatases with regard to substrate and magnesium cofactor, respectively. In this work, we report the crystal structure and reaction mechanism of Rattus norvegicus 3'-phosphoadenosine 5'-phosphate and inositol 1,4-bisphosphate phosphatase (RnPIP), a recently identified target of lithium therapy. This Li(+)-sensitive enzyme plays a crucial role in several cellular processes, such as RNA processing, sulphation reactions and probably inositol recycling. RnPIP specifically removes the 3'-phosphate group of 3'-phosphoadenosine 5'-phosphate (PAP) and the 1'-phosphate group of inositol 1,4-bisphosphate (I(1),(4)P(2)) producing AMP and inositol 4'-phosphate, respectively. The crystal structure of RnPIP complexed with AMP, Pi and magnesium ions at 1.69 A resolution provides insight into the reaction mechanism of the hydrolysis of PAP. The core fold of the enzyme is equivalent to that found in other Li(+)-sensitive phosphatases, such as inositol monophosphatase, but molecular modelling of I(1),(4)P(2) in the RnPIP active site reveals important structural determinants that accommodate this additional substrate. RnPIP is potently inhibited by lithium and, as the accumulation of PAP inhibits a variety of proteins, including sulphotransferases and RNA processing enzymes, this dual specificity enzyme represents a potential target of lithium action, in addition to inositol monophosphatases.
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Affiliation(s)
- S Patel
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge, CB2 1GA, UK
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Abstract
Recent progress has been made in the characterization of cation transporters that maintain ion homeostasis during salt stress in plants. Sodium-proton antiporters at the vacuolar (NHX1) and plasma membrane (SOS1) have been identified in Arabidopsis. SOS1 is regulated by the calcium-activated protein kinase complex SOS2-SOS3. In yeast, a transcription repressor, Sko1, mediates regulation of the sodium-pump ENA1 gene by the Hog1 MAP kinase. The recent visualization at the atomic level of the inhibitory site of sodium in the known target Hal2 has helped identify the interactions determining Na(+) toxicity.
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Affiliation(s)
- R Serrano
- Instituto de Biología Molecular y Celular de Plantas Universidad Politécnica de Valencia-C.S.I.C., Camino de Vera, 46022, Valencia, Spain.
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Mora A, Sabio G, González-Polo RA, Cuenda A, Alessi DR, Alonso JC, Fuentes JM, Soler G, Centeno F. Lithium inhibits caspase 3 activation and dephosphorylation of PKB and GSK3 induced by K+ deprivation in cerebellar granule cells. J Neurochem 2001; 78:199-206. [PMID: 11432986 DOI: 10.1046/j.1471-4159.2001.00410.x] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Lithium protects cerebellar granule cells from apoptosis induced by low potassium, and also from other apoptotic stimuli. However, the precise mechanism by which this occurs is not understood. When cerebellar granule cells were switched to low potassium medium, the activation of caspase 3 was detected within 6 h, suggesting a role of caspase 3 in mediating apoptosis under conditions of low potassium. In the same conditions, lithium (5 mM) inhibited the activation of caspase 3 induced by low potassium. As lithium did not inhibit caspase 3 activity in vitro, these results suggest that this ion inhibits an upstream component that is required for caspase 3 activation. Lithium is known to inhibit a kinase termed glycogen sythase kinase 3 (GSK3), which is implicated in the survival pathway of phosphatidylinositol 3-kinase/protein kinase B (PI3K/PKB). Here we demonstrate that low potassium in the absence of lithium induces the dephosphorylation, and therefore the activation, of GSK3. However, when lithium was present, GSK3 remained phosphorylated at the same level as observed under conditions of high potassium. Low potassium induced the dephosphorylation and inactivation of PKB, whereas when lithium was present PKB was not dephosphorylated. Our results allow us to propose a new hypothesis about the action mechanism of lithium, this ion could inhibit a serine-threonine phosphatase induced by potassium deprivation.
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Affiliation(s)
- A Mora
- Departamento de Bioquímica y Biología Molecular, Facultad de Veterinaria, Universidad de Extremadura, Avenue Universidad s/n, 10071 Cáceres, Spain
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Abstract
Lithium is highly effective in the treatment of bipolar disorder and also has multiple effects on embryonic development, glycogen synthesis, hematopoiesis, and other processes. However, the mechanism of lithium action is still unclear. A number of enzymes have been proposed as potential targets of lithium action, including inositol monophosphatase, a family of structurally related phosphomonoesterases, and the protein kinase glycogen synthase kinase-3. These potential targets are widely expressed, require metal ions for catalysis, and are generally inhibited by lithium in an uncompetitive manner, most likely by displacing a divalent cation. Thus, the challenge is to determine which target, if any, is responsible for a given response to lithium in cells. Comparison of lithium effects with genetic disruption of putative target molecules has helped to validate these targets, and the use of alternative inhibitors of a given target can also lend strong support for or against a proposed mechanism of lithium action. In this review, lithium sensitive enzymes are discussed, and a number of criteria are proposed to evaluate which of these enzymes are involved in the response to lithium in a given setting.
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Affiliation(s)
- C J Phiel
- Department of Medicine and Howard Hughes Medical Institute, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104. USA.
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