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Varga JK, Diffley K, Welker Leng KR, Fierke CA, Schueler-Furman O. Structure-based prediction of HDAC6 substrates validated by enzymatic assay reveals determinants of promiscuity and detects new potential substrates. Sci Rep 2022; 12:1788. [PMID: 35110592 PMCID: PMC8810773 DOI: 10.1038/s41598-022-05681-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Accepted: 01/17/2022] [Indexed: 01/25/2023] Open
Abstract
Histone deacetylases play important biological roles well beyond the deacetylation of histone tails. In particular, HDAC6 is involved in multiple cellular processes such as apoptosis, cytoskeleton reorganization, and protein folding, affecting substrates such as ɑ-tubulin, Hsp90 and cortactin proteins. We have applied a biochemical enzymatic assay to measure the activity of HDAC6 on a set of candidate unlabeled peptides. These served for the calibration of a structure-based substrate prediction protocol, Rosetta FlexPepBind, previously used for the successful substrate prediction of HDAC8 and other enzymes. A proteome-wide screen of reported acetylation sites using our calibrated protocol together with the enzymatic assay provide new peptide substrates and avenues to novel potential functional regulatory roles of this promiscuous, multi-faceted enzyme. In particular, we propose novel regulatory roles of HDAC6 in tumorigenesis and cancer cell survival via the regulation of EGFR/Akt pathway activation. The calibration process and comparison of the results between HDAC6 and HDAC8 highlight structural differences that explain the established promiscuity of HDAC6.
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Affiliation(s)
- Julia K Varga
- Department of Microbiology and Molecular Genetics, Institute for Medical Research Israel-Canada (IMRIC), The Hebrew University of Jerusalem, Faculty of Medicine, POB 12272, 9112102, Jerusalem, Israel
| | - Kelsey Diffley
- Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, MI, 48109, USA
| | - Katherine R Welker Leng
- Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, MI, 48109, USA
| | - Carol A Fierke
- Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, MI, 48109, USA
- Department of Biochemistry, Brandeis University, 415 South Street, Waltham, MA, 02453, USA
| | - Ora Schueler-Furman
- Department of Microbiology and Molecular Genetics, Institute for Medical Research Israel-Canada (IMRIC), The Hebrew University of Jerusalem, Faculty of Medicine, POB 12272, 9112102, Jerusalem, Israel.
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2
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GlcNAc De- N-Acetylase from the Hyperthermophilic Archaeon Sulfolobus solfataricus. Appl Environ Microbiol 2019; 85:AEM.01879-18. [PMID: 30446550 DOI: 10.1128/aem.01879-18] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Accepted: 11/04/2018] [Indexed: 01/17/2023] Open
Abstract
Sulfolobus solfataricus is an aerobic crenarchaeal hyperthermophile with optimum growth at temperatures greater than 80°C and pH 2 to 4. Within the crenarchaeal group of Sulfolobales, N-acetylglucosamine (GlcNAc) has been shown to be a component of exopolysaccharides, forming their biofilms, and of the N-glycan decorating some proteins. The metabolism of GlcNAc is still poorly understood in Archaea, and one approach to gaining additional information is through the identification and functional characterization of carbohydrate active enzymes (CAZymes) involved in the modification of GlcNAc. The screening of S. solfataricus extracts allowed the detection of a novel α-N-acetylglucosaminidase (α-GlcNAcase) activity, which has never been identified in Archaea Mass spectrometry analysis of the purified activity showed a protein encoded by the sso2901 gene. Interestingly, the purified recombinant enzyme, which was characterized in detail, revealed a novel de-N-acetylase activity specific for GlcNAc and derivatives. Thus, assays to identify an α-GlcNAcase found a GlcNAc de-N-acetylase instead. The α-GlcNAcase activity observed in S. solfataricus extracts did occur when SSO2901 was used in combination with an α-glucosidase. Furthermore, the inspection of the genomic context and the preliminary characterization of a putative glycosyltransferase immediately upstream of sso2901 (sso2900) suggest the involvement of these enzymes in the GlcNAc metabolism in S. solfataricus IMPORTANCE In this study, a preliminary screening of cellular extracts of S. solfataricus allowed the identification of an α-N-acetylglucosaminidase activity. However, the characterization of the corresponding recombinant enzyme revealed a novel GlcNAc de-N-acetylase, which, in cooperation with the α-glucosidase, catalyzed the hydrolysis of O-α-GlcNAc glycosides. In addition, we show that the product of a gene flanking the one encoding the de-N-acetylase is a putative glycosyltransferase, suggesting the involvement of the two enzymes in the metabolism of GlcNAc. The discovery and functional analysis of novel enzymatic activities involved in the modification of this essential sugar represent a powerful strategy to shed light on the physiology and metabolism of Archaea.
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Castañeda CA, Wolfson NA, Leng KR, Kuo YM, Andrews AJ, Fierke CA. HDAC8 substrate selectivity is determined by long- and short-range interactions leading to enhanced reactivity for full-length histone substrates compared with peptides. J Biol Chem 2017; 292:21568-21577. [PMID: 29109148 PMCID: PMC5766737 DOI: 10.1074/jbc.m117.811026] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Revised: 10/05/2017] [Indexed: 01/03/2023] Open
Abstract
Histone deacetylases (HDACs) catalyze deacetylation of acetyl-lysine residues within proteins. To date, HDAC substrate specificity and selectivity have been largely estimated using peptide substrates. However, it is unclear whether peptide substrates accurately reflect the substrate selectivity of HDAC8 toward full-length proteins. Here, we compare HDAC8 substrate selectivity in the context of peptides, full-length proteins, and protein-nucleic acid complexes. We demonstrate that HDAC8 catalyzes deacetylation of tetrameric histone (H3/H4) substrates with catalytic efficiencies that are 40-300-fold higher than those for corresponding peptide substrates. Thus, we conclude that additional contacts with protein substrates enhance catalytic efficiency. However, the catalytic efficiency decreases for larger multiprotein complexes. These differences in HDAC8 substrate selectivity for peptides and full-length proteins suggest that HDAC8 substrate preference is based on a combination of short- and long-range interactions. In summary, this work presents detailed kinetics for HDAC8-catalyzed deacetylation of singly-acetylated, full-length protein substrates, revealing that HDAC8 substrate selectivity is determined by multiple factors. These insights provide a foundation for understanding recognition of full-length proteins by HDACs.
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Affiliation(s)
| | | | - Katherine R Leng
- Chemistry, University of Michigan, Ann Arbor, Michigan 48109 and
| | - Yin-Ming Kuo
- the Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111
| | | | - Carol A Fierke
- From the Program in Chemical Biology and
- the Departments of Biological Chemistry and
- Chemistry, University of Michigan, Ann Arbor, Michigan 48109 and
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4
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Huang X, Hernick M. Recombinant expression of a functional myo-inositol-1-phosphate synthase (MIPS) in Mycobacterium smegmatis. Protein J 2016; 34:380-90. [PMID: 26420670 DOI: 10.1007/s10930-015-9632-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Myo-inositol-1-phosphate synthase (MIPS, E.C. 5.5.1.4) catalyzes the first step in inositol production-the conversion of glucose-6-phosphate (Glc-6P) to myo-inositol-1-phosphate. While the three dimensional structure of MIPS from Mycobacterium tuberculosis has been solved, biochemical studies examining the in vitro activity have not been reported to date. Herein we report the in vitro activity of mycobacterial MIPS expressed in E. coli and Mycobacterium smegmatis. Recombinant expression in E. coli yields a soluble protein capable of binding the NAD(+) cofactor; however, it has no significant activity with the Glc-6P substrate. In contrast, recombinant expression in M. smegmatis mc(2)4517 yields a functionally active protein. Examination of structural data suggests that MtMIPS expressed in E. coli adopts a fold that is missing a key helix containing two critical (conserved) Lys side chains, which likely explains the inability of the E. coli expressed protein to bind and turnover the Glc-6P substrate. Recombinant expression in M. smegmatis may yield a protein that adopts a fold in which this key helix is formed enabling proper positioning of important side chains, thereby allowing for Glc-6P substrate binding and turnover. Detailed mechanistic studies may be feasible following optimization of the recombinant MIPS expression protocol in M. smegmatis.
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Affiliation(s)
- Xinyi Huang
- Department of Biochemistry, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Marcy Hernick
- Department of Biochemistry, Virginia Tech, Blacksburg, VA, 24061, USA. .,Department of Pharmaceutical Sciences, Appalachian College of Pharmacy, Oakwood, VA, 24631, USA.
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5
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Toro TB, Watt TJ. KDAC8 substrate specificity quantified by a biologically relevant, label-free deacetylation assay. Protein Sci 2015; 24:2020-32. [PMID: 26402585 DOI: 10.1002/pro.2813] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Revised: 08/21/2015] [Accepted: 09/20/2015] [Indexed: 01/25/2023]
Abstract
Analysis of the human proteome has identified thousands of unique protein sequences that contain acetylated lysine residues in vivo. These modifications regulate a variety of biological processes and are reversed by the lysine deacetylase (KDAC) family of enzymes. Despite the known prevalence and importance of acetylation, the details of KDAC substrate recognition are not well understood. While several methods have been developed to monitor protein deacetylation, none are particularly suited for identifying enzyme-substrate pairs of label-free substrates across the entire family of lysine deacetylases. Here, we present a fluorescamine-based assay which is more biologically relevant than existing methods and amenable to probing substrate specificity. Using this assay, we evaluated the activity of KDAC8 and other lysine deacetylases, including a sirtuin, for several peptides derived from known acetylated proteins. KDAC8 showed clear preferences for some peptides over others, indicating that the residues immediately surrounding the acetylated lysine play an important role in substrate specificity. Steady-state kinetics suggest that the sequence surrounding the acetylated lysine affects binding affinity and catalytic rate independently. Our results provide direct evidence that potential KDAC8 substrates previously identified through cell based experiments can be directly deacetylated by KDAC8. Conversely, the data from this assay did not correlate well with predictions from previous screens for KDAC8 substrates using less biologically relevant substrates and assay conditions. Combining results from our assay with mass spectrometry-based experiments and cell-based experiments will allow the identification of specific KDAC-substrate pairs and lead to a better understanding of the biological consequences of these interactions.
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Affiliation(s)
- Tasha B Toro
- Department of Chemistry, Xavier University of Louisiana, New Orleans, Louisiana, 70125
| | - Terry J Watt
- Department of Chemistry, Xavier University of Louisiana, New Orleans, Louisiana, 70125
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Huang X, Hernick M. Molecular Determinants of N-Acetylglucosamine Recognition and Turnover by N-Acetyl-1-d-myo-inosityl-2-amino-2-deoxy-α-d-glucopyranoside Deacetylase (MshB). Biochemistry 2015; 54:3784-90. [DOI: 10.1021/acs.biochem.5b00068] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Xinyi Huang
- Department
of Biochemistry, Virginia Tech, Blacksburg, Virginia 24061, United States
| | - Marcy Hernick
- Department
of Biochemistry, Virginia Tech, Blacksburg, Virginia 24061, United States
- Department
of Pharmaceutical Sciences, Appalachian College of Pharmacy, Oakwood, Virginia 24631, United States
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7
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Si M, Long M, Chaudhry MT, Xu Y, Zhang P, Zhang L, Shen X. Functional characterization of Corynebacterium glutamicum mycothiol S-conjugate amidase. PLoS One 2014; 9:e115075. [PMID: 25514023 PMCID: PMC4267739 DOI: 10.1371/journal.pone.0115075] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2014] [Accepted: 11/18/2014] [Indexed: 11/18/2022] Open
Abstract
The present study focuses on the genetic and biochemical characterization of mycothiol S-conjugate amidase (Mca) of Corynebacterium glutamicum. Recombinant C. glutamicum Mca was heterologously expressed in Escherichia coli and purified to apparent homogeneity. The molecular weight of native Mca protein determined by gel filtration chromatography was 35 kDa, indicating that Mca exists as monomers in the purification condition. Mca showed amidase activity with mycothiol S-conjugate of monobromobimane (MSmB) in vivo while mca mutant lost the ability to cleave MSmB. In addition, Mca showed limited deacetylase activity with N-acetyl-D-glucosamine (GlcNAc) as substrate. Optimum pH for amidase activity was between 7.5 and 8.5, while the highest activity in the presence of Zn2+ confirmed Mca as a zinc metalloprotein. Amino acid residues conserved among Mca family members were located in C. glutamicum Mca and site-directed mutagenesis of these residues indicated that Asp14, Tyr137, His139 and Asp141 were important for activity. The mca deletion mutant showed decreased resistance to antibiotics, alkylating agents, oxidants and heavy metals, and these sensitive phenotypes were recovered in the complementary strain to a great extent. The physiological roles of Mca in resistance to various toxins were further supported by the induced expression of Mca in C. glutamicum under various stress conditions, directly under the control of the stress-responsive extracytoplasmic function-sigma (ECF-σ) factor SigH.
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Affiliation(s)
- Meiru Si
- State Key Laboratory of Crop Stress Biology for Arid Areas and College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, China
| | - Mingxiu Long
- College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi, China
| | - Muhammad Tausif Chaudhry
- Environmental Analytical Laboratory, National Physical & Standards Laboratory, PCSIR, Islamabad, Pakistan
| | - Yixiang Xu
- State Key Laboratory of Crop Stress Biology for Arid Areas and College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, China
| | - Pan Zhang
- State Key Laboratory of Crop Stress Biology for Arid Areas and College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, China
| | - Lei Zhang
- State Key Laboratory of Crop Stress Biology for Arid Areas and College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, China
| | - Xihui Shen
- State Key Laboratory of Crop Stress Biology for Arid Areas and College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, China
- * E-mail:
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8
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Wolfson NA, Pitcairn CA, Sullivan ED, Joseph CG, Fierke CA. An enzyme-coupled assay measuring acetate production for profiling histone deacetylase specificity. Anal Biochem 2014; 456:61-9. [PMID: 24674948 PMCID: PMC4470474 DOI: 10.1016/j.ab.2014.03.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Revised: 02/24/2014] [Accepted: 03/13/2014] [Indexed: 11/17/2022]
Abstract
Histone deacetylases catalyze the hydrolysis of an acetyl group from post-translationally modified acetyl-lysine residues in a wide variety of essential cellular proteins, including histones. Because these lysine modifications can alter the activity and properties of affected proteins, aberrant acetylation/deacetylation may contribute to disease states. Many fundamental questions regarding the substrate specificity and regulation of these enzymes have yet to be answered. Here, we optimize an enzyme-coupled assay to measure low micromolar concentrations of acetate, coupling acetate production to the formation of NADH (nicotinamide adenine dinucleotide, reduced form) that is measured by changes in either absorbance or fluorescence. Using this assay, we measured the steady-state kinetics of peptides representing the H4 histone tail and demonstrate that a C-terminally conjugated methylcoumarin enhances the catalytic efficiency of deacetylation catalyzed by cobalt(II)-bound histone deacetylase 8 [Co(II)-HDAC8] compared with peptide substrates containing a C-terminal carboxylate, amide, and tryptophan by 50-, 2.8-, and 2.3-fold, respectively. This assay can be adapted for a high-throughput screening format to identify HDAC substrates and inhibitors.
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Affiliation(s)
- Noah A Wolfson
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
| | - Carol Ann Pitcairn
- Interdepartmental Program in Chemical Biology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Eric D Sullivan
- Interdepartmental Program in Chemical Biology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Caleb G Joseph
- Department of Medicinal Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
| | - Carol A Fierke
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, USA; Interdepartmental Program in Chemical Biology, University of Michigan, Ann Arbor, MI 48109, USA; Department of Medicinal Chemistry, University of Michigan, Ann Arbor, MI 48109, USA; Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA.
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9
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Hernick M. Mycothiol: a target for potentiation of rifampin and other antibiotics againstMycobacterium tuberculosis. Expert Rev Anti Infect Ther 2014; 11:49-67. [DOI: 10.1586/eri.12.152] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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10
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Cross-functionalities of Bacillus deacetylases involved in bacillithiol biosynthesis and bacillithiol-S-conjugate detoxification pathways. Biochem J 2013; 454:239-47. [PMID: 23758290 DOI: 10.1042/bj20130415] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
BshB, a key enzyme in bacillithiol biosynthesis, hydrolyses the acetyl group from N-acetylglucosamine malate to generate glucosamine malate. In Bacillus anthracis, BA1557 has been identified as the N-acetylglucosamine malate deacetylase (BshB); however, a high content of bacillithiol (~70%) was still observed in the B. anthracis ∆BA1557 strain. Genomic analysis led to the proposal that another deacetylase could exhibit cross-functionality in bacillithiol biosynthesis. In the present study, BA1557, its paralogue BA3888 and orthologous Bacillus cereus enzymes BC1534 and BC3461 have been characterized for their deacetylase activity towards N-acetylglucosamine malate, thus providing biochemical evidence for this proposal. In addition, the involvement of deacetylase enzymes is also expected in bacillithiol-detoxifying pathways through formation of S-mercapturic adducts. The kinetic analysis of bacillithiol-S-bimane conjugate favours the involvement of BA3888 as the B. anthracis bacillithiol-S-conjugate amidase (Bca). The high degree of specificity of this group of enzymes for its physiological substrate, along with their similar pH-activity profile and Zn²⁺-dependent catalytic acid-base reaction provides further evidence for their cross-functionalities.
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11
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Spry C, Macuamule C, Lin Z, Virga KG, Lee RE, Strauss E, Saliba KJ. Pantothenamides are potent, on-target inhibitors of Plasmodium falciparum growth when serum pantetheinase is inactivated. PLoS One 2013; 8:e54974. [PMID: 23405100 PMCID: PMC3566143 DOI: 10.1371/journal.pone.0054974] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2012] [Accepted: 12/21/2012] [Indexed: 12/26/2022] Open
Abstract
Growth of the virulent human malaria parasite Plasmodium falciparum is dependent on an extracellular supply of pantothenate (vitamin B(5)) and is susceptible to inhibition by pantothenate analogues that hinder pantothenate utilization. In this study, on the hunt for pantothenate analogues with increased potency relative to those reported previously, we screened a series of pantothenamides (amide analogues of pantothenate) against P. falciparum and show for the first time that analogues of this type possess antiplasmodial activity. Although the active pantothenamides in this series exhibit only modest potency under standard in vitro culture conditions, we show that the potency of pantothenamides is selectively enhanced when the parasite culture medium is pre-incubated at 37°C for a prolonged period. We present evidence that this finding is linked to the presence in Albumax II (a serum-substitute routinely used for in vitro cultivation of P. falciparum) of pantetheinase activity: the activity of an enzyme that hydrolyzes the pantothenate metabolite pantetheine, for which pantothenamides also serve as substrates. Pantetheinase activity, and thereby pantothenamide degradation, is reduced following incubation of Albumax II-containing culture medium for a prolonged period at 37°C, revealing the true, sub-micromolar potency of pantothenamides. Importantly we show that the potent antiplasmodial effect of pantothenamides is attenuated with pantothenate, consistent with the compounds inhibiting parasite proliferation specifically by inhibiting pantothenate and/or CoA utilization. Additionally, we show that the pantothenamides interact with P. falciparum pantothenate kinase, the first enzyme involved in converting pantothenate to coenzyme A. This is the first demonstration of on-target antiplasmodial pantothenate analogues with sub-micromolar potency, and highlights the potential of pantetheinase-resistant pantothenamides as antimalarial agents.
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Affiliation(s)
- Christina Spry
- Research School of Biology, College of Medicine, Biology and Environment, The Australian National University, Canberra, Australian Capital Territory, Australia
| | - Cristiano Macuamule
- Department of Biochemistry, Stellenbosch University, Matieland, Stellenbosch, South África
| | - Zhiyang Lin
- Research School of Biology, College of Medicine, Biology and Environment, The Australian National University, Canberra, Australian Capital Territory, Australia
| | - Kristopher G. Virga
- Department of Pharmaceutical and Administrative Sciences, Presbyterian College School of Pharmacy, Clinton, South Carolina, United States of America
- Department of Pharmaceutical Sciences, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
| | - Richard E. Lee
- Department of Pharmaceutical Sciences, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
- Department of Chemical Biology and Therapeutics, St. Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
| | - Erick Strauss
- Department of Biochemistry, Stellenbosch University, Matieland, Stellenbosch, South África
| | - Kevin J. Saliba
- Research School of Biology, College of Medicine, Biology and Environment, The Australian National University, Canberra, Australian Capital Territory, Australia
- Medical School, College of Medicine, Biology and Environment, The Australian National University, Canberra, Australian Capital Territory, Australia
- * E-mail:
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12
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Fahey RC. Glutathione analogs in prokaryotes. Biochim Biophys Acta Gen Subj 2012; 1830:3182-98. [PMID: 23075826 DOI: 10.1016/j.bbagen.2012.10.006] [Citation(s) in RCA: 147] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Revised: 09/25/2012] [Accepted: 10/08/2012] [Indexed: 01/17/2023]
Abstract
BACKGROUND Oxygen is both essential and toxic to all forms of aerobic life and the chemical versatility and reactivity of thiols play a key role in both aspects. Cysteine thiol groups have key catalytic functions in enzymes but are readily damaged by reactive oxygen species (ROS). Low-molecular-weight thiols provide protective buffers against the hazards of ROS toxicity. Glutathione is the small protective thiol in nearly all eukaryotes but in prokaryotes the situation is far more complex. SCOPE OF REVIEW This review provides an introduction to the diversity of low-molecular-weight thiol protective systems in bacteria. The topics covered include the limitations of cysteine as a protector, the multiple origins and distribution of glutathione biosynthesis, mycothiol biosynthesis and function in Actinobacteria, recent discoveries involving bacillithiol found in Firmicutes, new insights on the biosynthesis and distribution of ergothioneine, and the potential protective roles played by coenzyme A and other thiols. MAJOR CONCLUSIONS Bacteria have evolved a diverse collection of low-molecular-weight protective thiols to deal with oxygen toxicity and environmental challenges. Our understanding of how many of these thiols are produced and utilized is still at an early stage. GENERAL SIGNIFICANCE Extensive diversity existed among prokaryotes prior to evolution of the cyanobacteria and the development of an oxidizing atmosphere. Bacteria that managed to adapt to life under oxygen evolved, or acquired, the ability to produce a variety of small thiols for protection against the hazards of aerobic metabolism. Many pathogenic prokaryotes depend upon novel thiol protection systems that may provide targets for new antibacterial agents. This article is part of a Special Issue entitled Cellular functions of glutathione.
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Affiliation(s)
- Robert C Fahey
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093, USA.
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13
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Nokwequ MG, Nkambule CM, Gammon DW. Armed–disarmed effect on the stability of cysteine thioglucosides. Carbohydr Res 2012; 359:18-23. [DOI: 10.1016/j.carres.2012.06.022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2012] [Revised: 06/22/2012] [Accepted: 06/30/2012] [Indexed: 11/25/2022]
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14
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Lamprecht DA, Muneri NO, Eastwood H, Naidoo KJ, Strauss E, Jardine A. An enzyme-initiated Smiles rearrangement enables the development of an assay of MshB, the GlcNAc-Ins deacetylase of mycothiol biosynthesis. Org Biomol Chem 2012; 10:5278-88. [PMID: 22678300 DOI: 10.1039/c2ob25429h] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
MshB is the N-acetyl-1-D-myo-inosityl-2-amino-2-deoxy-D-glucopyranoside (GlcNAc-Ins) deacetylase active as one of the enzymes involved in the biosynthesis of mycothiol (MSH), a protective low molecular weight thiol present only in Mycobacterium tuberculosis and other actinomycetes. In this study, structural analogues of GlcNAc-Ins in which the inosityl moiety is replaced by a chromophore were synthesized and evaluated as alternate substrates of MshB, with the goal of identifying a compound that would be useful in high-throughput assays of the enzyme. In an unexpected and surprising finding one of the GlcNAc-Ins analogues is shown to undergo a Smiles rearrangement upon MshB-mediated deacetylation, uncovering a free thiol group. We demonstrate that this chemistry can be exploited for the development of the first continuous assay of MshB activity based on the detection of thiol formation by DTNB (Ellman's reagent); such an assay should be ideally suited for the identification of MshB inhibitors by means of high-throughput screens in microplates.
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Affiliation(s)
- Dirk A Lamprecht
- Department of Biochemistry, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa
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15
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Huang X, Hernick M. Examination of mechanism of N-acetyl-1-D-myo-inosityl-2-amino-2-deoxy-α-D-glucopyranoside deacetylase (MshB) reveals unexpected role for dynamic tyrosine. J Biol Chem 2012; 287:10424-10434. [PMID: 22315231 DOI: 10.1074/jbc.m111.320184] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Actinomycetes are a group of gram-positive bacteria that includes pathogenic mycobacterial species, such as Mycobacterium tuberculosis. These organisms do not have glutathione and instead utilize the small molecule mycothiol (MSH) as their primary reducing agent and for the detoxification of xenobiotics. Due to these important functions, enzymes involved in MSH biosynthesis and MSH-dependent detoxification are targets for drug development. The metal-dependent deacetylase N-acetyl-1-D-myo-inosityl-2-amino-2-deoxy-α-D-glucopyranoside deacetylase (MshB) catalyzes the hydrolysis of N-acetyl-1-D-myo-inosityl-2-amino-2-deoxy-α-D-glucopyranoside to form 1-D-myo-inosityl-2-amino-2-deoxy-α-D-glucopyranoside and acetate in MSH biosynthesis. Herein we examine the chemical mechanism of MshB. We demonstrate that the side chains of Asp-15, Tyr-142, His-144, and Asp-146 are important for catalytic activity. We show that NaF is an uncompetitive inhibitor of MshB, consistent with a metal-water/hydroxide functioning as the reactive nucleophile in the catalytic mechanism. We have previously shown that MshB activity has a bell-shaped dependence on pH with pK(a) values of ∼7.3 and 10.5 (Huang, X., Kocabas, E. and Hernick, M. (2011) J. Biol. Chem. 286, 20275-20282). Mutagenesis experiments indicate that the observed pK(a) values reflect ionization of Asp-15 and Tyr-142, respectively. Together, findings from our studies suggest that MshB functions through a general acid-base pair mechanism with the side chain of Asp-15 functioning as the general base catalyst and His-144 serving as the general acid catalyst, whereas the side chain of Tyr-142 probably assists in polarizing substrate/stabilizing the oxyanion intermediate. Additionally, our results indicate that Tyr-142 is a dynamic side chain that plays key roles in catalysis, modulating substrate binding, chemistry, and product release.
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Affiliation(s)
- Xinyi Huang
- Department of Biochemistry, Virginia Tech, Blacksburg, Virginia 24061
| | - Marcy Hernick
- Department of Biochemistry, Virginia Tech, Blacksburg, Virginia 24061.
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Huang X, Kocabas E, Hernick M. The activity and cofactor preferences of N-acetyl-1-D-myo-inosityl-2-amino-2-deoxy-alpha-D-glucopyranoside deacetylase (MshB) change depending on environmental conditions. J Biol Chem 2011; 286:20275-82. [PMID: 21507949 DOI: 10.1074/jbc.m111.234229] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Actinomycetes, such as Mycobacterium species, are Gram-positive bacteria that utilize the small molecule mycothiol (MSH) as their primary reducing agent. Consequently, the enzymes involved in MSH biosynthesis are targets for drug development. The metal-dependent enzyme N-acetyl-1-D-myo-inosityl-2-amino-2-deoxy-α-D-glucopyranoside deacetylase (MshB) catalyzes the hydrolysis of N-acetyl-1-D-myo-inosityl-2-amino-2-deoxy-α-D-glucopyranoside to form 1-D-myo-inosityl-2-amino-2-deoxy-α-D-glucopyranoside and acetate, the fourth overall step in MSH biosynthesis. Inhibitors of metalloenzymes typically contain a group that binds to the active site metal ion; thus, a comprehensive understanding of the native cofactor(s) of metalloenzymes is critical for the development of biologically effective inhibitors. Herein, we examined the effect of metal ions on the overall activity of MshB and probed the identity of the native cofactor. We found that the activity of MshB follows the trend Fe(2+) > Co(2+) > Zn(2+) > Mn(2+) and Ni(2+). Additionally, our results show that the identity of the cofactor bound to purified MshB is highly dependent on the purification conditions used (aerobic versus anaerobic), as well as the metal ion content of the medium during protein expression. MshB prefers Fe(2+) under anaerobic conditions regardless of the metal ion content of the medium and switches between Fe(2+) and Zn(2+) under aerobic conditions as the metal content of the medium is altered. These results indicate that the cofactor bound to MshB under biological conditions is dependent on environmental conditions, suggesting that MshB may be a cambialistic metallohydrolase that contains a dynamic cofactor. Consequently, biologically effective inhibitors will likely need to dually target Fe(2+)-MshB and Zn(2+)-MshB.
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Affiliation(s)
- Xinyi Huang
- Department of Biochemistry, Virginia Tech, Blacksburg, Virginia 24061, USA
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