1
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Azevedo C, Borghi F, Su XB, Saiardi A. On the covalent nature of lysine polyphosphorylation. Mol Cell 2024; 84:1811-1815.e3. [PMID: 38701742 DOI: 10.1016/j.molcel.2024.03.029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2023] [Revised: 03/22/2024] [Accepted: 03/29/2024] [Indexed: 05/05/2024]
Abstract
Post-translational modifications of proteins (PTMs) introduce an extra layer of complexity to cellular regulation. Although phosphorylation of serine, threonine, and tyrosine residues is well-known as PTMs, lysine is, in fact, the most heavily modified amino acid, with over 30 types of PTMs on lysine having been characterized. One of the most recently discovered PTMs on lysine residues is polyphosphorylation, which sees linear chains of inorganic polyphosphates (polyP) attached to lysine residues. The labile nature of phosphoramidate bonds raises the question of whether this modification is covalent in nature. Here, we used buffers with very high ionic strength, which would disrupt any non-covalent interactions, and confirmed that lysine polyphosphorylation occurs covalently on proteins containing PASK domains (polyacidic, serine-, and lysine-rich), such as the budding yeast protein nuclear signal recognition 1 (Nsr1) and the mammalian protein nucleolin. This Matters Arising Response paper addresses the Neville et al. (2024) Matters Arising paper, published concurrently in Molecular Cell.
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Affiliation(s)
- Cristina Azevedo
- Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK; InnovPlantProtect, Estrada Gil Vaz, 7350-478 Elvas, Portugal
| | - Filipy Borghi
- Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK
| | - Xue Bessie Su
- Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK
| | - Adolfo Saiardi
- Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK.
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2
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Neville N, Lehotsky K, Klupt KA, Downey M, Jia Z. Polyphosphate attachment to lysine repeats is a non-covalent protein modification. Mol Cell 2024; 84:1802-1810.e4. [PMID: 38701741 DOI: 10.1016/j.molcel.2024.03.028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2023] [Revised: 03/12/2024] [Accepted: 03/29/2024] [Indexed: 05/05/2024]
Abstract
Polyphosphate (polyP) is a chain of inorganic phosphate that is present in all domains of life and affects diverse cellular phenomena, ranging from blood clotting to cancer. A study by Azevedo et al. described a protein modification whereby polyP is attached to lysine residues within polyacidic serine and lysine (PASK) motifs via what the authors claimed to be covalent phosphoramidate bonding. This was based largely on the remarkable ability of the modification to survive extreme denaturing conditions. Our study demonstrates that lysine polyphosphorylation is non-covalent, based on its sensitivity to ionic strength and lysine protonation and absence of phosphoramidate bond formation, as analyzed via 31P NMR. Ionic interaction with lysine residues alone is sufficient for polyP modification, and we present a new list of non-PASK lysine repeat proteins that undergo polyP modification. This work clarifies the biochemistry of polyP-lysine modification, with important implications for both studying and modulating this phenomenon. This Matters Arising paper is in response to Azevedo et al. (2015), published in Molecular Cell. See also the Matters Arising Response by Azevedo et al. (2024), published in this issue.
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Affiliation(s)
- Nolan Neville
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON K7L 3N6, Canada
| | - Kirsten Lehotsky
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON K7L 3N6, Canada
| | - Kody A Klupt
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON K7L 3N6, Canada
| | - Michael Downey
- Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada; Ottawa Institute of Systems Biology, Ottawa, ON K1H 8M5, Canada
| | - Zongchao Jia
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON K7L 3N6, Canada.
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3
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Zong G, Desfougères Y, Portela-Torres P, Kwon YU, Saiardi A, Shears SB, Wang H. Biochemical and structural characterization of an inositol pyrophosphate kinase from a giant virus. EMBO J 2024; 43:462-480. [PMID: 38216735 PMCID: PMC10897400 DOI: 10.1038/s44318-023-00005-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Revised: 11/11/2023] [Accepted: 11/15/2023] [Indexed: 01/14/2024] Open
Abstract
Kinases that synthesize inositol phosphates (IPs) and pyrophosphates (PP-IPs) control numerous biological processes in eukaryotic cells. Herein, we extend this cellular signaling repertoire to viruses. We have biochemically and structurally characterized a minimalist inositol phosphate kinase (i.e., TvIPK) encoded by Terrestrivirus, a nucleocytoplasmic large ("giant") DNA virus (NCLDV). We show that TvIPK can synthesize inositol pyrophosphates from a range of scyllo- and myo-IPs, both in vitro and when expressed in yeast cells. We present multiple crystal structures of enzyme/substrate/nucleotide complexes with individual resolutions from 1.95 to 2.6 Å. We find a heart-shaped ligand binding pocket comprising an array of positively charged and flexible side chains, underlying the observed substrate diversity. A crucial arginine residue in a conserved "G-loop" orients the γ-phosphate of ATP to allow substrate pyrophosphorylation. We highlight additional conserved catalytic and architectural features in TvIPK, and support their importance through site-directed mutagenesis. We propose that NCLDV inositol phosphate kinases may have assisted evolution of inositol pyrophosphate signaling, and we discuss the potential biogeochemical significance of TvIPK in soil niches.
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Affiliation(s)
- Guangning Zong
- Inositol Signaling Group, Signal Transduction Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, 27709, USA
| | - Yann Desfougères
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, UK
| | - Paloma Portela-Torres
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, UK
| | - Yong-Uk Kwon
- Department of Chemistry and Nanoscience, Ewha Womans University, 52, Ewhayeodae-gil, Seodaemun-gu, Seoul, 03760, South Korea
| | - Adolfo Saiardi
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, UK.
| | - Stephen B Shears
- Inositol Signaling Group, Signal Transduction Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, 27709, USA.
| | - Huanchen Wang
- Inositol Signaling Group, Signal Transduction Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, 27709, USA.
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4
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Gauthier CM, LeGallais J, Savic N, Moradi-Fard S, Grew A, Loe M, Kirlikaya B, Cobb J, Nelson CJ. Intrinsic disorder of a nucleoplasmin-like histone chaperone specifies its discrete nuclear and nucleolar functions. FEBS Lett 2024; 598:187-198. [PMID: 38058218 DOI: 10.1002/1873-3468.14783] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Revised: 11/16/2023] [Accepted: 11/21/2023] [Indexed: 12/08/2023]
Abstract
Nucleoplasmin (NPM) histone chaperones regulate distinct processes in the nucleus and nucleolus. While intrinsically disordered regions (IDRs) are hallmarks of NPMs, it is not clear whether all NPM functions require these unstructured features. We assessed the importance of IDRs in a yeast NPM-like protein and found that regulation of rDNA copy number and genetic interactions with the nucleolar RNA surveillance machinery require the highly conserved FKBP prolyl isomerase domain, but not the NPM domain or IDRs. By contrast, transcriptional repression in the nucleus requires IDRs. Furthermore, multiple lysines in polyacidic serine/lysine motifs of IDRs are required for both lysine polyphosphorylation and NPM-mediated transcriptional repression. These results demonstrate that this NPM-like protein relies on IDRs only for some of its chromatin-related functions.
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Affiliation(s)
| | - Josey LeGallais
- Department of Biochemistry and Microbiology, University of Victoria, Canada
| | - Neda Savic
- Department of Biochemistry and Microbiology, University of Victoria, Canada
| | - Sarah Moradi-Fard
- Departments of Biochemistry & Molecular Biology and Oncology, Robson DNA Science Centre, Arnie Charbonneau Cancer Institute, Cumming School of Medicine, University of Calgary, Calgary, Canada
| | - Arden Grew
- Department of Biochemistry and Microbiology, University of Victoria, Canada
| | - Martin Loe
- Department of Biochemistry and Microbiology, University of Victoria, Canada
| | - Baran Kirlikaya
- Department of Biochemistry and Microbiology, University of Victoria, Canada
| | - Jennifer Cobb
- Department of Biochemistry and Microbiology, University of Victoria, Canada
- Departments of Biochemistry & Molecular Biology and Oncology, Robson DNA Science Centre, Arnie Charbonneau Cancer Institute, Cumming School of Medicine, University of Calgary, Calgary, Canada
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5
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Neville N, Lehotsky K, Yang Z, Klupt KA, Denoncourt A, Downey M, Jia Z. Modification of histidine repeat proteins by inorganic polyphosphate. Cell Rep 2023; 42:113082. [PMID: 37660293 DOI: 10.1016/j.celrep.2023.113082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2023] [Revised: 06/29/2023] [Accepted: 08/16/2023] [Indexed: 09/05/2023] Open
Abstract
Inorganic polyphosphate (polyP) is a linear polymer of orthophosphate that is present in nearly all organisms studied to date. A remarkable function of polyP involves its attachment to lysine residues via non-enzymatic post-translational modification (PTM), which is presumed to be covalent. Here, we show that proteins containing tracts of consecutive histidine residues exhibit a similar modification by polyP, which confers an electrophoretic mobility shift on NuPAGE gels. Our screen uncovers 30 human and yeast histidine repeat proteins that undergo histidine polyphosphate modification (HPM). This polyP modification is histidine dependent and non-covalent in nature, although remarkably it withstands harsh denaturing conditions-a hallmark of covalent PTMs. Importantly, we show that HPM disrupts phase separation and the phosphorylation activity of the human protein kinase DYRK1A, and inhibits the activity of the transcription factor MafB, highlighting HPM as a potential protein regulatory mechanism.
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Affiliation(s)
- Nolan Neville
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON K7L 3N6, Canada
| | - Kirsten Lehotsky
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON K7L 3N6, Canada
| | - Zhiyun Yang
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON K7L 3N6, Canada
| | - Kody A Klupt
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON K7L 3N6, Canada
| | - Alix Denoncourt
- Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada; Ottawa Institute of Systems Biology, Ottawa, ON K1H 8M5, Canada
| | - Michael Downey
- Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada; Ottawa Institute of Systems Biology, Ottawa, ON K1H 8M5, Canada
| | - Zongchao Jia
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON K7L 3N6, Canada.
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6
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Kitamura N, Galligan JJ. A global view of the human post-translational modification landscape. Biochem J 2023; 480:1241-1265. [PMID: 37610048 PMCID: PMC10586784 DOI: 10.1042/bcj20220251] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Revised: 07/26/2023] [Accepted: 08/07/2023] [Indexed: 08/24/2023]
Abstract
Post-translational modifications (PTMs) provide a rapid response to stimuli, finely tuning metabolism and gene expression and maintain homeostasis. Advances in mass spectrometry over the past two decades have significantly expanded the list of known PTMs in biology and as instrumentation continues to improve, this list will surely grow. While many PTMs have been studied in detail (e.g. phosphorylation, acetylation), the vast majority lack defined mechanisms for their regulation and impact on cell fate. In this review, we will highlight the field of PTM research as it currently stands, discussing the mechanisms that dictate site specificity, analytical methods for their detection and study, and the chemical tools that can be leveraged to define PTM regulation. In addition, we will highlight the approaches needed to discover and validate novel PTMs. Lastly, this review will provide a starting point for those interested in PTM biology, providing a comprehensive list of PTMs and what is known regarding their regulation and metabolic origins.
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Affiliation(s)
- Naoya Kitamura
- Department of Pharmacology and College of Pharmacy, University of Arizona, Tucson, Arizona 85721, U.S.A
| | - James J. Galligan
- Department of Pharmacology and College of Pharmacy, University of Arizona, Tucson, Arizona 85721, U.S.A
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7
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Sanchez AM, Garg A, Schwer B, Shuman S. Inorganic polyphosphate abets silencing of a sub-telomeric gene cluster in fission yeast. MICROPUBLICATION BIOLOGY 2023; 2023:10.17912/micropub.biology.000744. [PMID: 36820394 PMCID: PMC9938405 DOI: 10.17912/micropub.biology.000744] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Figures] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Revised: 01/25/2023] [Accepted: 02/03/2023] [Indexed: 02/24/2023]
Abstract
Inorganic polyphosphate is a ubiquitous polymer with myriad roles in cell and organismal physiology. Whereas there is evidence for nuclear polyphosphate, its impact on transcriptional regulation in eukaryotes is unkown. Transcriptional profiling of fission yeast cells lacking polyphosphate (via deletion of the catalytic subunit Vtc4 of the Vtc4/Vtc2 polyphosphate polymerase complex) elicited de-repression of four protein-coding genes located within the right sub-telomeric arm of chromosome I that is known to be transcriptionally silenced by the TORC2 complex. These genes were equally de-repressed in vtc2 ∆ cells and in cells expressing polymerase-dead Vtc4, signifying that polyphosphate synthesis is required for repression of these sub-telomeric genes.
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Affiliation(s)
- Ana M. Sanchez
- Molecular Biology, Memorial Sloan Kettering Cancer Center, New York, New York, United States
- Gerstner Sloan Kettering Graduate School of Biomedical Sciences, New York, New York, United States
| | - Angad Garg
- Molecular Biology, Memorial Sloan Kettering Cancer Center, New York, New York, United States
| | - Beate Schwer
- Microbiology and Immunology, Weill Cornell Medicine, New York, New York, United States
| | - Stewart Shuman
- Molecular Biology, Memorial Sloan Kettering Cancer Center, New York, New York, United States
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8
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Choi SY, Choi W, Park YS, Kim HK, Kim YH, Min J. Vacuoles isolated from Saccharomyces cerevisiae inhibit differentiation of 3T3-L1 adipocyte. Enzyme Microb Technol 2023; 163:110165. [DOI: 10.1016/j.enzmictec.2022.110165] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Revised: 11/01/2022] [Accepted: 11/21/2022] [Indexed: 11/25/2022]
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9
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James SW, Palmer J, Keller NP, Brown ML, Dunworth MR, Francisco SG, Watson KG, Titchen B, Achimovich A, Mahoney A, Artemiou JP, Buettner KG, Class M, Sydenstricker AL, Anglin SL. A reciprocal translocation involving Aspergillus nidulans snxAHrb1/Gbp2 and gyfA uncovers a new regulator of the G2-M transition and reveals a role in transcriptional repression for the setBSet2 histone H3-lysine-36 methyltransferase. Genetics 2022; 222:iyac130. [PMID: 36005881 PMCID: PMC9526064 DOI: 10.1093/genetics/iyac130] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Accepted: 08/09/2022] [Indexed: 12/24/2022] Open
Abstract
Aspergillus nidulans snxA, an ortholog of Saccharomyces cerevisiae Hrb1/Gbp2 messenger RNA shuttle proteins, is-in contrast to budding yeast-involved in cell cycle regulation, in which snxA1 and snxA2 mutations as well as a snxA deletion specifically suppress the heat sensitivity of mutations in regulators of the CDK1 mitotic induction pathway. snxA mutations are strongly cold sensitive, and at permissive temperature snxA mRNA and protein expression are strongly repressed. Initial attempts to identify the causative snxA mutations revealed no defects in the SNXA protein. Here, we show that snxA1/A2 mutations resulted from an identical chromosome I-II reciprocal translocation with breakpoints in the snxA first intron and the fourth exon of a GYF-domain gene, gyfA. Surprisingly, a gyfA deletion and a reconstructed gyfA translocation allele suppressed the heat sensitivity of CDK1 pathway mutants in a snxA+ background, demonstrating that 2 unrelated genes, snxA and gyfA, act through the CDK1-CyclinB axis to restrain the G2-M transition, and for the first time identifying a role in G2-M regulation for a GYF-domain protein. To better understand snxA1/A2-reduced expression, we generated suppressors of snxA cold sensitivity in 2 genes: (1) loss of the abundant nucleolar protein Nsr1/nucleolin bypassed the requirement for snxA and (2) loss of the Set2 histone H3 lysine36 (H3K36) methyltransferase or a nonmethylatable histone H3K36L mutant rescued hypomorphic snxA mutants by restoring full transcriptional proficiency, indicating that methylation of H3K36 acts normally to repress snxA transcription. These observations are in line with known Set2 functions in preventing excessive and cryptic transcription of active genes.
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Affiliation(s)
- Steven W James
- Department of Biology, Gettysburg College, Gettysburg, PA 17325, USA
| | - Jonathan Palmer
- Data Analytics, Genencor Technology Center, IFF, Palo Alto, CA, 94306, USA
| | - Nancy P Keller
- Department of Medical Microbiology and Immunology, University of Wisconsin—Madison, Madison, WI 53726, USA
| | - Morgan L Brown
- Department of Cell and Developmental Biology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Matthew R Dunworth
- Department of Cell Biology, Johns Hopkins School of Medicine, Baltimore, MD 21218, USA
| | - Sarah G Francisco
- Department of Otolaryngology, Boston Children’s Hospital, Boston, MA 02115, USA
| | - Katherine G Watson
- School of Medicine, Noorda College of Osteopathic Medicine, Provo, UT 84606, USA
| | - Breanna Titchen
- Department of Biological and Biomedical Sciences, Harvard University, Cambridge, MA 02138, USA
| | - Alecia Achimovich
- Department of Chemistry, Gettysburg College, Gettysburg, PA 17325, USA
| | - Andrew Mahoney
- Department of Chemistry, Emory University, Atlanta, GA 30322, USA
| | | | - Kyra G Buettner
- School of Medicine, Thomas Jefferson University, Philadelphia, PA 19144, USA
| | - Madelyn Class
- School of Medicine, Temple University, Philadelphia, PA 19140, USA
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10
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Ddp1 Cooperates with Ppx1 to Counter a Stress Response Initiated by Nonvacuolar Polyphosphate. mBio 2022; 13:e0039022. [PMID: 35862758 PMCID: PMC9426566 DOI: 10.1128/mbio.00390-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In diverse cells from bacterial to mammalian species, inorganic phosphate is stored in long chains called polyphosphate (polyP). These nearly universal polymers, ranging from three to thousands of phosphate moieties in length, are associated with molecular functions, including energy homeostasis, protein folding, and cell signaling. In many cell types, polyphosphate is concentrated in subcellular compartments or organelles. In the budding yeast Saccharomyces cerevisiae, polyP synthesis by the membrane-bound vacuolar transporter chaperone (VTC) complex is coupled to its translocation into the lumen of the vacuole, a lysosome-like organelle, where it is stored at high concentrations. In contrast, the ectopic expression of the bacterial polyphosphate kinase (PPK) results in the toxic accumulation of polyP outside the vacuole. In this study, we used label-free mass spectrometry to investigate the mechanisms underlying this toxicity. We find that PPK expression results in the activation of a stress response mediated in part by the Hog1 and Yak1 kinases and the Msn2/Msn4 transcription factors as well as by changes in protein kinase A (PKA) activity. This response is countered by the combined action of the Ddp1 and Ppx1 polyphosphatases that function together to counter polyP accumulation and downstream toxicity. In contrast, the ectopic expression of previously proposed mammalian polyphosphatases did not impact PPK-mediated toxicity in this model, suggesting either that these enzymes do not function directly as polyphosphatases in vivo or that they require cofactors unique to higher eukaryotes. Our work provides insight into why polyP accumulation outside lysosome-like organelles is toxic. Furthermore, it serves as a resource for exploring how polyP may impact conserved biological processes at a molecular level.
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11
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Blocking Polyphosphate Mobilization Inhibits Pho4 Activation and Virulence in the Pathogen Candida albicans. mBio 2022; 13:e0034222. [PMID: 35575514 PMCID: PMC9239153 DOI: 10.1128/mbio.00342-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
The ability of pathogenic fungi to obtain essential nutrients from the host is vital for virulence. In Candida albicans, acquisition of the macronutrient phosphate is regulated by the Pho4 transcription factor and is important for both virulence and resistance to host-encountered stresses. All cells store phosphate in the form of polyphosphate (polyP), a ubiquitous polymer comprising tens to hundreds of phosphate residues. Release of phosphate from polyP is one of the first responses evoked in response to phosphate starvation, and here, we sought to explore the importance of polyP mobilization in the pathobiology of C. albicans. We found that two polyphosphatases, Ppn1 and Ppx1, function redundantly to release phosphate from polyP in C. albicans. Strikingly, we reveal that blocking polyP mobilization prevents the activation of the Pho4 transcription factor: following Pi starvation, Pho4 fails to accumulate in the nucleus and induce Pi acquisition genes in ppn1Δ ppx1Δ cells. Consequently, ppn1Δ ppx1Δ cells display impaired resistance to the same range of stresses that require Pho4 for survival. In addition, cells lacking both polyphosphatases are exquisitely sensitive to DNA replication stress, indicating that polyP mobilization is needed to support the phosphate-demanding process of DNA replication. Blocking polyP mobilization also results in significant morphological defects, as ppn1Δ ppx1Δ cells form large pseudohypha-like cells that are resistant to serum-induced hypha formation. Thus, polyP mobilization impacts key processes important for the pathobiology of C. albicans, and consistent with this, we found that blocking this process attenuates the virulence of this important human fungal pathogen.
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12
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Shepard SM, Jessen HJ, Cummins CC. Beyond Triphosphates: Reagents and Methods for Chemical Oligophosphorylation. J Am Chem Soc 2022; 144:7517-7530. [PMID: 35471019 DOI: 10.1021/jacs.1c07990] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Oligophosphates play essential roles in biochemistry, and considerable research has been directed toward the synthesis of both naturally occurring oligophosphates and their synthetic analogues. Greater attention has been given to mono-, di-, and triphosphates, as these are present in higher concentrations biologically and easier to synthesize. However, extended oligophosphates have potent biochemical roles, ranging from blood coagulation to HIV drug resistance. Sporadic reports have slowly built a niche body of literature related to the synthesis and study of extended oligophosphates, but newfound interests and developments have the potential to rapidly expand this field. Here we report on current methods to synthesize oligophosphates longer than triphosphates and comment on the most important future directions for this area of research. The state of the art has provided fairly robust methods for synthesizing nucleoside 5'-tetra- and pentaphosphates as well as dinucleoside 5',5'-oligophosphates. Future research should endeavor to push such syntheses to longer oligophosphates while developing synthetic methodologies for rarer morphologies such as 3'-nucleoside oligophosphates, polyphosphates, and phosphonate/thiophosphate analogues of these species.
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Affiliation(s)
- Scott M Shepard
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge Massachusetts 02139, United States
| | - Henning J Jessen
- Institute of Organic Chemistry, University of Freiburg & Cluster of Excellence livMatS, FIT - Freiburg Center for Interactive Materials and Bioinspired Technologies, University of Freiburg, Georges-Köhler-Allee 105, D-79110 Freiburg, Germany
| | - Christopher C Cummins
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge Massachusetts 02139, United States
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13
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Cleavage-Polyadenylation Factor Cft1 and SPX Domain Proteins Are Agents of Inositol Pyrophosphate Toxicosis in Fission Yeast. mBio 2022; 13:e0347621. [PMID: 35012333 PMCID: PMC8749416 DOI: 10.1128/mbio.03476-21] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Inositol pyrophosphate (IPP) dynamics govern expression of the fission yeast phosphate homeostasis regulon via their effects on lncRNA-mediated transcription interference. The growth defects (ranging from sickness to lethality) elicited by fission yeast mutations that inactivate IPP pyrophosphatase enzymes are exerted via the agonistic effects of too much 1,5-IP8 on RNA 3'-processing and transcription termination. To illuminate determinants of IPP toxicosis, we conducted a genetic screen for spontaneous mutations that suppressed the sickness of Asp1 pyrophosphatase mutants. We identified a missense mutation, C823R, in the essential Cft1 subunit of the cleavage and polyadenylation factor complex that suppresses even lethal Asp1 IPP pyrophosphatase mutations, thereby fortifying the case for 3'-processing/termination as the target of IPP toxicity. The suppressor screen also identified Gde1 and Spx1 (SPAC6B12.07c), both of which have an IPP-binding SPX domain and both of which are required for lethality elicited by Asp1 mutations. A survey of other SPX proteins in the proteome identified the Vtc4 and Vtc2 subunits of the vacuolar polyphosphate polymerase as additional agents of IPP toxicosis. Gde1, Spx1, and Vtc4 contain enzymatic modules (glycerophosphodiesterase, RING finger ubiquitin ligase, and polyphosphate polymerase, respectively) fused to their IPP-sensing SPX domains. Structure-guided mutagenesis of the IPP-binding sites and the catalytic domains of Gde1 and Spx1 indicated that both modules are necessary to elicit IPP toxicity. Whereas Vtc4 polymerase catalytic activity is required for IPP toxicity, its IPP-binding site is not. Epistasis analysis, transcriptome profiling, and assays of Pho1 expression implicate Spx1 as a transducer of IP8 signaling to the 3'-processing/transcription termination machinery. IMPORTANCE Impeding the catabolism of the inositol pyrophosphate (IPP) signaling molecule IP8 is cytotoxic to fission yeast. Here, by performing a genetic suppressor screen, we identified several cellular proteins required for IPP toxicosis. Alleviation of IPP lethality by a missense mutation in the essential Cft1 subunit of the cleavage and polyadenylation factor consolidates previous evidence that toxicity results from IP8 action as an agonist of RNA 3'-processing and transcription termination. Novel findings are that IP8 toxicity depends on IPP-sensing SPX domain proteins with associated enzymatic functions: Gde1 (glycerophosphodiesterase), Spx1 (ubiquitin ligase), and Vtc2/4 (polyphosphate polymerase). The effects of Spx1 deletion on phosphate homeostasis imply a role for Spx1 in communicating an IP8-driven signal to the transcription and RNA processing apparatus.
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14
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The Histidine Ammonia Lyase of Trypanosoma cruzi Is Involved in Acidocalcisome Alkalinization and Is Essential for Survival under Starvation Conditions. mBio 2021; 12:e0198121. [PMID: 34724827 PMCID: PMC8561398 DOI: 10.1128/mbio.01981-21] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Trypanosoma cruzi, the agent of Chagas disease, accumulates polyphosphate (polyP) and Ca2+ inside acidocalcisomes. The alkalinization of this organelle stimulates polyP hydrolysis and Ca2+ release. Here, we report that histidine ammonia lyase (HAL), an enzyme that catalyzes histidine deamination with production of ammonia (NH3) and urocanate, is responsible for acidocalcisome alkalinization. Histidine addition to live parasites expressing HAL fused to the pH-sensitive emission biosensor green fluorescent protein (GFP) variant pHluorin induced alkalinization of acidocalcisomes. PolyP decreased HAL activity of epimastigote lysates or the recombinant protein but did not cause its polyphosphorylation, as determined by the lack of HAL electrophoretic shift on NuPAGE gels using both in vitro and in vivo conditions. We demonstrate that HAL binds strongly to polyP and localizes to the acidocalcisomes and cytosol of the parasite. Four lysine residues localized in the HAL C-terminal region are instrumental for its polyP binding, its inhibition by polyP, its function inside acidocalcisomes, and parasite survival under starvation conditions. Expression of HAL in yeast deficient in polyP degradation decreased cell fitness. This effect was enhanced by histidine and decreased when the lysine-rich C-terminal region was deleted. In conclusion, this study highlights a mechanism for stimulation of acidocalcisome alkalinization linked to amino acid metabolism.
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Tomashevsky A, Kulakovskaya E, Trilisenko L, Kulakovskiy IV, Kulakovskaya T, Fedorov A, Eldarov M. VTC4 Polyphosphate Polymerase Knockout Increases Stress Resistance of Saccharomyces cerevisiae Cells. BIOLOGY 2021; 10:487. [PMID: 34070801 PMCID: PMC8227513 DOI: 10.3390/biology10060487] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 05/26/2021] [Accepted: 05/27/2021] [Indexed: 11/17/2022]
Abstract
Inorganic polyphosphate (polyP) is an important factor of alkaline, heavy metal, and oxidative stress resistance in microbial cells. In yeast, polyP is synthesized by Vtc4, a subunit of the vacuole transporter chaperone complex. Here, we report reduced but reliably detectable amounts of acid-soluble and acid-insoluble polyPs in the Δvtc4 strain of Saccharomyces cerevisiae, reaching 10% and 20% of the respective levels of the wild-type strain. The Δvtc4 strain has decreased resistance to alkaline stress but, unexpectedly, increased resistance to oxidation and heavy metal excess. We suggest that increased resistance is achieved through elevated expression of DDR2, which is implicated in stress response, and reduced expression of PHO84 encoding a phosphate and divalent metal transporter. The decreased Mg2+-dependent phosphate accumulation in Δvtc4 cells is consistent with reduced expression of PHO84. We discuss a possible role that polyP level plays in cellular signaling of stress response mobilization in yeast.
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Affiliation(s)
- Alexander Tomashevsky
- Federal Scientific Center, Pushchino Research Center for Biology of the Russian Academy of Sciences, Skryabin Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, pr. Nauki 5, 142290 Pushchino, Russia; (A.T.); (E.K.); (L.T.)
| | - Ekaterina Kulakovskaya
- Federal Scientific Center, Pushchino Research Center for Biology of the Russian Academy of Sciences, Skryabin Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, pr. Nauki 5, 142290 Pushchino, Russia; (A.T.); (E.K.); (L.T.)
| | - Ludmila Trilisenko
- Federal Scientific Center, Pushchino Research Center for Biology of the Russian Academy of Sciences, Skryabin Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, pr. Nauki 5, 142290 Pushchino, Russia; (A.T.); (E.K.); (L.T.)
| | - Ivan V. Kulakovskiy
- Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, 119991 Moscow, Russia;
- Vavilov Institute of General Genetics, Russian Academy of Sciences, 119991 Moscow, Russia
| | - Tatiana Kulakovskaya
- Federal Scientific Center, Pushchino Research Center for Biology of the Russian Academy of Sciences, Skryabin Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, pr. Nauki 5, 142290 Pushchino, Russia; (A.T.); (E.K.); (L.T.)
| | - Alexey Fedorov
- Federal Scientific Center for Biotechnology of the Russian Academy of Sciences, Institute of Bioengineering, Russian Academy of Sciences, Leninsky prosp. 33-2, 119071 Moscow, Russia; (A.F.); (M.E.)
| | - Mikhail Eldarov
- Federal Scientific Center for Biotechnology of the Russian Academy of Sciences, Institute of Bioengineering, Russian Academy of Sciences, Leninsky prosp. 33-2, 119071 Moscow, Russia; (A.F.); (M.E.)
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Kulakovskaya TV, Andreeva NA, Ledova LA, Ryazanova LP, Trilisenko LV, Eldarov MA. Enzymes of Polyphosphate Metabolism in Yeast: Properties, Functions, Practical Significance. BIOCHEMISTRY (MOSCOW) 2021; 86:S96-S108. [PMID: 33827402 DOI: 10.1134/s0006297921140078] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Inorganic polyphosphates (polyP) are the linear polymers of orthophosphoric acid varying in the number of phosphate residues linked by the energy-rich phosphoanhydride bonds. PolyP is an essential component in living cells. Knowledge of polyP metabolizing enzymes in eukaryotes is necessary for understanding molecular mechanisms of polyP metabolism in humans and development of new approaches for treating bone and cardiovascular diseases associated with impaired mineral phosphorus metabolism. Yeast cells represent a rational experimental model for this research due to availability of the methods for studying phosphorus metabolism and construction of knockout mutants and strains overexpressing target proteins. Multicomponent system of polyP metabolism in Saccharomyces cerevisiae cells is presented in this review discussing properties, functioning, and practical significance of the enzymes involved in the synthesis and degradation of this important metabolite.
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Affiliation(s)
- Tatiana V Kulakovskaya
- Skryabin Institute of Biochemistry and Physiology of Microorganisms, Pushchino Research Center for Biology, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia.
| | - Nadezhda A Andreeva
- Skryabin Institute of Biochemistry and Physiology of Microorganisms, Pushchino Research Center for Biology, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
| | - Larisa A Ledova
- Skryabin Institute of Biochemistry and Physiology of Microorganisms, Pushchino Research Center for Biology, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
| | - Lubov P Ryazanova
- Skryabin Institute of Biochemistry and Physiology of Microorganisms, Pushchino Research Center for Biology, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
| | - Ludmila V Trilisenko
- Skryabin Institute of Biochemistry and Physiology of Microorganisms, Pushchino Research Center for Biology, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
| | - Michail A Eldarov
- Institute of Bioengineering, Federal Scientific Center for Biotechnology, Russian Academy of Sciences, Moscow, 117312, Russia
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Baijal K, Downey M. The promises of lysine polyphosphorylation as a regulatory modification in mammals are tempered by conceptual and technical challenges. Bioessays 2021; 43:e2100058. [PMID: 33998006 DOI: 10.1002/bies.202100058] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2021] [Revised: 04/13/2021] [Accepted: 04/16/2021] [Indexed: 12/17/2022]
Abstract
Polyphosphate (polyP) is a ubiquitous biomolecule thought to be present in all cells on Earth. PolyP is deceivingly simple, consisting of repeated units of inorganic phosphates polymerized in long energy-rich chains. PolyP is involved in diverse functions in mammalian systems-from cell signaling to blood clotting. One exciting avenue of research is a new nonenzymatic post-translational modification, termed lysine polyphosphorylation, wherein polyP chains are covalently attached to lysine residues of target proteins. While the modification was first characterized in budding yeast, recent work has now identified the first human targets. There is significant promise in this area of biomedical research, but a number of technical issues and knowledge gaps present challenges to rapid progress. In this review, the current state of the field is summarized and existing roadblocks related to the study of lysine polyphosphorylation in higher eukaryotes are introduced. It is discussed how limited methods to identify targets of polyphosphorylation are further impacted by low concentration, unknown regulatory enzymes, and sequestration of polyP into compartments in mammalian systems. Furthermore, suggestions on how these obstacles could be addressed or what their physiological relevance may be within mammalian cells are presented.
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Affiliation(s)
- Kanchi Baijal
- Department of Cellular & Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada.,Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, Ontario, Canada
| | - Michael Downey
- Department of Cellular & Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada.,Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, Ontario, Canada
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18
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Shepard SM, Kim H, Bang QX, Alhokbany N, Cummins CC. Synthesis of α,δ-Disubstituted Tetraphosphates and Terminally-Functionalized Nucleoside Pentaphosphates. J Am Chem Soc 2020; 143:463-470. [PMID: 33375782 DOI: 10.1021/jacs.0c11884] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The anion [P4O11]2-, employed as its bis(triphenylphosphine)iminium (PPN) salt, is shown herein to be a versatile reagent for nucleophile tetraphosphorylation. Treatment under anhydrous conditions with an alkylamine base and a nucleophile (HNuc1), such as an alcohol (neopentanol, cyclohexanol, 4-methylumbelliferone, and Boc-Tyr-OMe), an amine (propargylamine, diethylamine, morpholine, 3,5-dimethylaniline, and isopropylamine), dihydrogen phosphate, phenylphosphonate, azide ion, or methylidene triphenylphosphorane, results in nucleophile substituted tetrametaphosphates ([P4O11Nuc1]3-) as mixed PPN and alkylammonium salts in 59% to 99% yield. Treatment of the resulting functionalized tetrametaphosphates with a second nucleophile (HNuc2), such as hydroxide, a phenol (4-methylumbelliferone), an amine (propargylamine and ethanolamine), fluoride, or a nucleoside monophosphate (uridine monophosphate, deoxyadenosine monophosphate, and adenosine monophosphate), results in ring opening to linear tetraphosphates bearing one nucleophile on each end ([Nuc1(PO3)3PO2Nuc2]4-). When necessary, these linear tetraphosphates are purified by reverse phase or anion exchange HPLC, yielding triethylammonium or ammonium salts in 32% to 92% yield from [PPN]2[P4O11]. Phosphorylation of methylidene triphenylphosphorane as Nuc1 yields a new tetrametaphosphate-based ylide ([Ph3PCHP4O11]3-, 94% yield). Wittig olefination of 2',3'-O-isopropylidene-5'-deoxy-5'-uridylaldehyde using this ylide results in a 3'-deoxy-3',4'-didehydronucleotide derivative, isolated as the triethylammonium salt in 54% yield.
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Affiliation(s)
- Scott M Shepard
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307, United States
| | - Hyehwang Kim
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307, United States
| | - Qing Xin Bang
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307, United States
| | - Norah Alhokbany
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307, United States
| | - Christopher C Cummins
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307, United States
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Mandala VS, Loh DM, Shepard SM, Geeson MB, Sergeyev IV, Nocera DG, Cummins CC, Hong M. Bacterial Phosphate Granules Contain Cyclic Polyphosphates: Evidence from 31P Solid-State NMR. J Am Chem Soc 2020; 142:18407-18421. [PMID: 33075224 DOI: 10.1021/jacs.0c06335] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Polyphosphates (polyPs) are ubiquitous polymers in living organisms from bacteria to mammals. They serve a wide variety of biological functions, ranging from energy storage to stress response. In the last two decades, polyPs have been primarily viewed as linear polymers with varying chain lengths. However, recent biochemical data show that small metaphosphates, cyclic oligomers of [PO3](-), can bind to the enzymes ribonuclease A and NAD kinase, raising the question of whether metaphosphates can occur naturally as products of biological activity. Before the 1980s, metaphosphates had been reported in polyPs extracted from various organisms, but these results are considered artifactual due to the extraction and purification protocols. Here, we employ nondestructive 31P solid-state NMR spectroscopy to investigate the chemical structure of polyphosphates in whole cells as well as insoluble fractions of the bacterium Xanthobacter autotrophicus. Isotropic and anisotropic 31P chemical shifts of hydrated whole cells indicate the coexistence of linear and cyclic phosphates. Under our cell growth conditions and the concentrated conditions of the solid-state NMR samples, we found substantial amounts of cyclic phosphates in X. autotrophicus, suggesting that in fresh cells metaphosphate concentrations can be significant. The cellular metaphosphates are identified by comparison with the 31P chemical shift anisotropy of synthetic metaphosphates of known structures. In X. autotrophicus, the metaphosphates have a chemical shift anisotropy that is consistent with an average size of 3-8 phosphate units. These metaphosphates are enriched in insoluble and electron-dense granules. Exogenous hexametaphosphate added to X. autotrophicus cell extracts is metabolized to trimetaphosphates, supporting the presence and biological role of metaphosphates in cells. The definitive evidence for the presence of metaphosphates, reported here in whole bacterial cells for the first time, opens the path for future investigations of the biological function of metaphosphates in many organisms.
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Affiliation(s)
- Venkata S Mandala
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, Massachusetts 02139, United States
| | - Daniel M Loh
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
| | - Scott M Shepard
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, Massachusetts 02139, United States
| | - Michael B Geeson
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, Massachusetts 02139, United States
| | - Ivan V Sergeyev
- Bruker Biospin, Billerica, Massachusetts 01821, United States
| | - Daniel G Nocera
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
| | - Christopher C Cummins
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, Massachusetts 02139, United States
| | - Mei Hong
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, Massachusetts 02139, United States
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20
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Austin S, Mayer A. Phosphate Homeostasis - A Vital Metabolic Equilibrium Maintained Through the INPHORS Signaling Pathway. Front Microbiol 2020; 11:1367. [PMID: 32765429 PMCID: PMC7381174 DOI: 10.3389/fmicb.2020.01367] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Accepted: 05/27/2020] [Indexed: 12/12/2022] Open
Abstract
Cells face major changes in demand for and supply of inorganic phosphate (Pi). Pi is often a limiting nutrient in the environment, particularly for plants and microorganisms. At the same time, the need for phosphate varies, establishing conflicts of goals. Cells experience strong peaks of Pi demand, e.g., during the S-phase, when DNA, a highly abundant and phosphate-rich compound, is duplicated. While cells must satisfy these Pi demands, they must safeguard themselves against an excess of Pi in the cytosol. This is necessary because Pi is a product of all nucleotide-hydrolyzing reactions. An accumulation of Pi shifts the equilibria of these reactions and reduces the free energy that they can provide to drive endergonic metabolic reactions. Thus, while Pi starvation may simply retard growth and division, an elevated cytosolic Pi concentration is potentially dangerous for cells because it might stall metabolism. Accordingly, the consequences of perturbed cellular Pi homeostasis are severe. In eukaryotes, they range from lethality in microorganisms such as yeast (Sethuraman et al., 2001; Hürlimann, 2009), severe growth retardation and dwarfism in plants (Puga et al., 2014; Liu et al., 2015; Wild et al., 2016) to neurodegeneration or renal Fanconi syndrome in humans (Legati et al., 2015; Ansermet et al., 2017). Intracellular Pi homeostasis is thus not only a fundamental topic of cell biology but also of growing interest for medicine and agriculture.
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Affiliation(s)
- Sisley Austin
- Département de Biochimie, Université de Lausanne, Lausanne, Switzerland
| | - Andreas Mayer
- Département de Biochimie, Université de Lausanne, Lausanne, Switzerland
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Abstract
Lysine polyphosphorylation (K-PPn) is a relatively new post-translational modification, the full targets and functional consequences of which are unknown. A critical problem in the study of endogenous K-PPn of proteins in the yeast model system is that its nonenzymatic nature and its susceptibility to polyphosphatases make it potentially susceptible to artifacts during extraction. A new study confirms that K-PPn modifications can be altered during sample handling, provides new insights into the mechanism of K-PPn, and develops a yeast model strain, devoid of both vacuolar polyP and polyphosphatases, that allows detection of authentic endogenous K-PPn.
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Affiliation(s)
- Roberto Docampo
- Center for Tropical and Emerging Global Diseases and Department of Cellular Biology, University of Georgia, Athens, Georgia 30602.
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