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Ruiz VG, Czyzyk DJ, Kumar VP, Jorgensen WL, Anderson KS. Targeting the TS dimer interface in bifunctional Cryptosporidium hominis TS-DHFR from parasitic protozoa: Virtual screening identifies novel TS allosteric inhibitors. Bioorg Med Chem Lett 2020; 30:127292. [PMID: 32631514 PMCID: PMC7376443 DOI: 10.1016/j.bmcl.2020.127292] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2020] [Revised: 05/23/2020] [Accepted: 05/26/2020] [Indexed: 12/20/2022]
Abstract
Effective therapies are lacking to treat gastrointestinal infections caused by the genus Cryptosporidium, which can be fatal in the immunocompromised. One target of interest is Cryptosporidium hominis (C. hominis) thymidylate synthase-dihydrofolate reductase (ChTS-DHFR), a bifunctional enzyme necessary for DNA biosynthesis. Targeting the TS-TS dimer interface is a novel strategy previously used to identify inhibitors against the related bifunctional enzyme in Toxoplasma gondii. In the present study, we target the ChTS dimer interface through homology modeling and high-throughput virtual screening to identifying allosteric, ChTS-specific inhibitors. Our work led to the discovery of methylenedioxyphenyl-aminophenoxypropanol analogues which inhibit ChTS activity in a manner that is both dose-dependent and influenced by the conformation of the enzyme. Preliminary results presented here include an analysis of structure activity relationships and a ChTS-apo crystal structure of ChTS-DHFR supporting the continued development of inhibitors that stabilize a novel pocket formed in the open conformation of ChTS-TS.
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Affiliation(s)
- Victor G Ruiz
- Department of Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
| | - Daniel J Czyzyk
- Department of Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
| | - Vidya P Kumar
- Department of Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA; Department of Chemistry, Yale University, 225 Prospect Street, PO Box 208107, New Haven, CT 06520-8107, USA; Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
| | - William L Jorgensen
- Department of Chemistry, Yale University, 225 Prospect Street, PO Box 208107, New Haven, CT 06520-8107, USA
| | - Karen S Anderson
- Department of Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA; Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA.
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Ruiz V, Czyzyk DJ, Valhondo M, Jorgensen WL, Anderson KS. Novel allosteric covalent inhibitors of bifunctional Cryptosporidium hominis TS-DHFR from parasitic protozoa identified by virtual screening. Bioorg Med Chem Lett 2019; 29:1413-1418. [PMID: 30929953 DOI: 10.1016/j.bmcl.2019.03.022] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Revised: 03/01/2019] [Accepted: 03/19/2019] [Indexed: 12/20/2022]
Abstract
Protozoans of the genus Cryptosporidium are the causative agent of the gastrointestinal disease, cryptosporidiosis, which can be fatal in immunocompromised individuals. Cryptosporidium hominis (C. hominis) bifunctional thymidylate synthase-dihydrofolate reductase (TS-DHFR) is an essential enzyme in the folate biosynthesis pathway and a molecular target for inhibitor design. Previous studies have demonstrated the importance of the ChTS-DHFR linker region "crossover helix" to the enzymatic activity and stability of the ChDHFR domain. We conducted a virtual screen of a novel non-active site pocket located at the interface of the ChDHFR domain and crossover helix. From this screen we have identified and characterized a noncompetitive inhibitor, compound 15, a substituted diphenyl thiourea. Through subsequent structure activity relationship studies, we have identified a time-dependent inhibitor lead, compound 15D17, a thiol-substituted 2-hydroxy-N-phenylbenzamide, which is selective for ChTS-DHFR, and whose effects appear to be mediated by covalent bond formation with a non-catalytic cysteine residue adjacent to the non-active site pocket.
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Affiliation(s)
- Victor Ruiz
- Department of Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
| | - Daniel J Czyzyk
- Department of Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
| | - Margarita Valhondo
- Department of Chemistry, Yale University, 225 Prospect Street, PO Box 208107, New Haven, CT 06520-8107, USA
| | - William L Jorgensen
- Department of Chemistry, Yale University, 225 Prospect Street, PO Box 208107, New Haven, CT 06520-8107, USA.
| | - Karen S Anderson
- Department of Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA; Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA.
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Anderson KS. Understanding the molecular mechanism of substrate channeling and domain communication in protozoal bifunctional TS-DHFR. Protein Eng Des Sel 2017; 30:253-261. [PMID: 28338744 PMCID: PMC6438133 DOI: 10.1093/protein/gzx004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Revised: 12/14/2016] [Accepted: 12/15/2016] [Indexed: 11/13/2022] Open
Abstract
Most species, such as humans, have monofunctional forms of thymidylate synthase (TS) and dihydrofolate reductase (DHFR) that are key folate metabolism enzymes making critical folate components required for DNA synthesis. In contrast, several parasitic protozoa, including Leishmania major (Lm), Plasmodium falciparum (Pf), Toxoplasma gondii (Tg) and Cryptosporidium hominis (Ch), contain a unique bifunctional thymidylate synthase-dihydrofolate reductase (TS-DHFR) having the two sequential catalytic activities contained on a single polypeptide chain. It has been suggested that the bifunctional nature of the two catalytic activities may enable substrate channeling. The 3D structures for each of these enzymes reveals distinct features for each species. While three of the four species (Pf, Tg and Ch) contain a junctional region linking the two domains, this is lacking in Lm. The Lm and Pf contain N-terminal amino acid extensions. A multidisciplinary approach using structural studies and transient kinetic analyses combined with mutational analysis has investigated the roles of these unique structural features for each enzyme. Additionally, the possibility of substrate channeling behavior was explored. These studies have identified unique, functional regions in both the TS and DHFR domains that govern efficient catalysis for each species. Surprisingly, even though there are structural similarities among the species, each is regulated in a distinct manner. This structural and mechanistic information was also used to exploit species-specific inhibitor design.
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Affiliation(s)
- Karen S. Anderson
- Departments of Pharmacology and Molecular Biophysics and Biochemistry,
Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520-8066, USA
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Chellan P, Sadler PJ, Land KM. Recent developments in drug discovery against the protozoal parasites Cryptosporidium and Toxoplasma. Bioorg Med Chem Lett 2017; 27:1491-1501. [PMID: 28242275 DOI: 10.1016/j.bmcl.2017.01.046] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2016] [Revised: 01/12/2017] [Accepted: 01/13/2017] [Indexed: 11/19/2022]
Abstract
Apicomplexan parasites cause some of the most devastating human diseases, including malaria, toxoplasmosis, and cryptosporidiosis. New drug discovery is imperative in light of increased resistance. In this digest article, we briefly explore some of the recent and promising developments in new drug discovery against two apicomplexan parasites, Cryptosporidium and Toxoplasma.
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Affiliation(s)
- Prinessa Chellan
- Department of Chemistry, University of Warwick, Coventry, Warwickshire CV4 7AL, UK
| | - Peter J Sadler
- Department of Chemistry, University of Warwick, Coventry, Warwickshire CV4 7AL, UK
| | - Kirkwood M Land
- Department of Biological Sciences, University of the Pacific, Stockton, CA 95211, United States.
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Kumar VP, Cisneros JA, Frey KM, Castellanos-Gonzalez A, Wang Y, Gangjee A, White AC, Jorgensen WL, Anderson KS. Structural studies provide clues for analog design of specific inhibitors of Cryptosporidium hominis thymidylate synthase-dihydrofolate reductase. Bioorg Med Chem Lett 2014; 24:4158-61. [PMID: 25127103 PMCID: PMC4427026 DOI: 10.1016/j.bmcl.2014.07.049] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Revised: 07/15/2014] [Accepted: 07/17/2014] [Indexed: 11/18/2022]
Abstract
Cryptosporidium is the causative agent of a gastrointestinal disease, cryptosporidiosis, which is often fatal in immunocompromised individuals and children. Thymidylate synthase (TS) and dihydrofolate reductase (DHFR) are essential enzymes in the folate biosynthesis pathway and are well established as drug targets in cancer, bacterial infections, and malaria. Cryptosporidium hominis has a bifunctional thymidylate synthase and dihydrofolate reductase enzyme, compared to separate enzymes in the host. We evaluated lead compound 1 from a novel series of antifolates, 2-amino-4-oxo-5-substituted pyrrolo[2,3-d]pyrimidines as an inhibitor of Cryptosporidium hominis thymidylate synthase with selectivity over the human enzyme. Complementing the enzyme inhibition compound 1 also has anti-cryptosporidial activity in cell culture. A crystal structure with compound 1 bound to the TS active site is discussed in terms of several van der Waals, hydrophobic and hydrogen bond interactions with the protein residues and the substrate analog 5-fluorodeoxyuridine monophosphate (TS), cofactor NADPH and inhibitor methotrexate (DHFR). Another crystal structure in complex with compound 1 bound in both the TS and DHFR active sites is also reported here. The crystal structures provide clues for analog design and for the design of ChTS-DHFR specific inhibitors.
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Affiliation(s)
- Vidya P Kumar
- Department of Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
| | - Jose A Cisneros
- Department of Chemistry, Yale University, 225 Prospect Street, PO Box 208107, New Haven, CT 06520-8107, USA
| | - Kathleen M Frey
- Department of Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
| | | | - Yiqiang Wang
- Division of Medicinal Chemistry, Graduate School of Pharmaceutical Sciences, Duquesne University, Pittsburgh, PA 15282, USA
| | - Aleem Gangjee
- Division of Medicinal Chemistry, Graduate School of Pharmaceutical Sciences, Duquesne University, Pittsburgh, PA 15282, USA.
| | - A Clinton White
- Infectious Disease Division, Department of Internal Medicine, University of Texas Medical Branch, Galveston, USA
| | - William L Jorgensen
- Department of Chemistry, Yale University, 225 Prospect Street, PO Box 208107, New Haven, CT 06520-8107, USA.
| | - Karen S Anderson
- Department of Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA.
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Bhat N, Wojczyk BS, DeCicco M, Castrodad C, Spitalnik SL, Ward HD. Identification of a family of four UDP-polypeptide N-acetylgalactosaminyl transferases in Cryptosporidium species. Mol Biochem Parasitol 2013; 191:24-7. [PMID: 23954365 PMCID: PMC3856541 DOI: 10.1016/j.molbiopara.2013.08.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2013] [Revised: 08/01/2013] [Accepted: 08/02/2013] [Indexed: 12/13/2022]
Abstract
Although mucin-type O-glycans are critical for Cryptosporidium infection, the enzymes catalyzing their synthesis have not been studied. Here, we report four UDP N-acetyl-α-D-galactosamine:polypeptide N-acetylgalactosaminyl transferases (ppGalNAc-Ts) from the genomes of C. parvum, C. hominis and C. muris. All are Type II membrane proteins which include a cytoplasmic tail, a transmembrane domain, a stem region, a glycosyltransferase family 2 domain and a C-terminal ricin B lectin domain. All are expressed during C. parvum infection in vitro, with Cp-ppGalNAc-T1 and -T4 expressed at 24 h and Cp-ppGalNAc-T2 and -T3 at 48 and 72 h post-infection, suggesting that their expression may be developmentally regulated. C. parvum sporozoite lysates display ppGalNAc-T enzymatic activity against non-glycosylated and pre-glycosylated peptides suggesting that they contain enzymes capable of glycosylating both types of substrates. The importance of mucin-type O-glycans in Cryptosporidium-host cell interactions raises the possibility that Cp-ppGalNAc-Ts may serve as targets for intervention in cryptosporidiosis.
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Affiliation(s)
- Najma Bhat
- Tufts Medical Center, Boston, MA, United States
| | - Boguslaw S. Wojczyk
- Department of Pathology and Cell Biology, College of Physicians and Surgeons of Columbia University, New York, NY, United States
| | - Maria DeCicco
- Tufts Medical Center, Boston, MA, United States
- Tufts University Sackler School of Graduate Medical Sciences, Boston, MA, United States
| | | | - Steven L. Spitalnik
- Department of Pathology and Cell Biology, College of Physicians and Surgeons of Columbia University, New York, NY, United States
| | - Honorine D. Ward
- Tufts Medical Center, Boston, MA, United States
- Tufts University Sackler School of Graduate Medical Sciences, Boston, MA, United States
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Manque PA, Woehlbier U, Lara AM, Tenjo F, Alves JM, Buck GA. Identification and characterization of a novel calcium-activated apyrase from Cryptosporidium parasites and its potential role in pathogenesis. PLoS One 2012; 7:e31030. [PMID: 22363541 PMCID: PMC3280346 DOI: 10.1371/journal.pone.0031030] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2011] [Accepted: 12/30/2011] [Indexed: 01/20/2023] Open
Abstract
Herein, we report the biochemical and functional characterization of a novel Ca2+-activated nucleoside diphosphatase (apyrase), CApy, of the intracellular gut pathogen Cryptosporidium. The purified recombinant CApy protein displayed activity, substrate specificity and calcium dependency strikingly similar to the previously described human apyrase, SCAN-1 (soluble calcium-activated nucleotidase 1). CApy was found to be expressed in both Cryptosporidium parvum oocysts and sporozoites, and displayed a polar localization in the latter, suggesting a possible co-localization with the apical complex of the parasite. In vitro binding experiments revealed that CApy interacts with the host cell in a dose-dependent fashion, implying the presence of an interacting partner on the surface of the host cell. Antibodies directed against CApy block Cryptosporidium parvum sporozoite invasion of HCT-8 cells, suggesting that CApy may play an active role during the early stages of parasite invasion. Sequence analyses revealed that the capy gene shares a high degree of homology with apyrases identified in other organisms, including parasites, insects and humans. Phylogenetic analysis argues that the capy gene is most likely an ancestral feature that has been lost from most apicomplexan genomes except Cryptosporidium, Neospora and Toxoplasma.
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Affiliation(s)
- Patricio A. Manque
- Department of Microbiology and Immunology, Virginia Commonwealth University, Richmond, Virginia, United States of America
- Center for the Study of Biological Complexity, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Ute Woehlbier
- Department of Microbiology and Immunology, Virginia Commonwealth University, Richmond, Virginia, United States of America
- Center for the Study of Biological Complexity, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Ana M. Lara
- Department of Microbiology and Immunology, Virginia Commonwealth University, Richmond, Virginia, United States of America
- Center for the Study of Biological Complexity, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Fernando Tenjo
- Department of Microbiology and Immunology, Virginia Commonwealth University, Richmond, Virginia, United States of America
- Center for the Study of Biological Complexity, Virginia Commonwealth University, Richmond, Virginia, United States of America
- Department of Biology, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - João M. Alves
- Department of Microbiology and Immunology, Virginia Commonwealth University, Richmond, Virginia, United States of America
- Center for the Study of Biological Complexity, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Gregory A. Buck
- Department of Microbiology and Immunology, Virginia Commonwealth University, Richmond, Virginia, United States of America
- Center for the Study of Biological Complexity, Virginia Commonwealth University, Richmond, Virginia, United States of America
- * E-mail:
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Abstract
BACKGROUND The trehalose synthetic pathway is present in bacteria, fungi, plants and invertebrate animals, but is absent in vertebrates. This disaccharide mainly functions as a stress protectant against desiccation, heat, cold and oxidation. Genes involved in trehalose synthesis have been observed in apicomplexan parasites, but little was known about these enzymes. Study on trehalose synthesis in apicomplexans would not only shed new light into the evolution of this pathway, but also provide data for exploring this pathway as novel drug target. METHODOLOGY/PRINCIPAL FINDINGS We have observed the presence of the trehalose synthetic pathway in Cryptosporidium and other apicomplexans and alveolates. Two key enzymes (trehalose 6-phosphate synthase [T6PS; EC 2.4.1.15] and trehalose phosphatase [TPase; EC 3.1.3.12] are present as Class II bifunctional proteins (T6PS-TPase) in the majority of apicomplexans with the exception of Plasmodium species. The enzyme for synthesizing the precursor (UDP-glucose) is homologous to dual-substrate UDP-galactose/glucose pyrophosphorylases (UGGPases), rather than the "classic" UDP-glucose pyrophosphorylase (UGPase). Phylogenetic recontructions indicate that both T6PS-TPases and UGGPases in apicomplexans and other alveolates are evolutionarily affiliated with stramenopiles and plants. The expression level of T6PS-TPase in C. parvum is highly elevated in the late intracellular developmental stage prior to or during the production of oocysts, implying that trehalose may be important in oocysts as a protectant against environmental stresses. Finally, trehalose has been detected in C. parvum oocysts, thus confirming the trehalose synthetic activity in this parasite. CONCLUSIONS/SIGNIFICANCE A trehalose synthetic pathway is described in the majority of apicomplexan parasites including Cryptosporidium and the presence of trehalose was confirmed in the C. parvum oocyst. Key enzymes in the pathway (i.e., T6PS-TPase and UGGPase) are plant-type and absent in humans and animals, and may potentially serve as novel drug targets in the apicomplexans.
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Affiliation(s)
- Yonglan Yu
- College of Veterinary Medicine, China Agricultural University, Beijing, China
- Department of Veterinary Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, Texas, United States of America
| | - Haili Zhang
- Department of Veterinary Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, Texas, United States of America
| | - Guan Zhu
- Department of Veterinary Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, Texas, United States of America
- Faculty of Genetics Program, Texas A&M University, College Station, Texas, United States of America
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Abstract
Cryptosporidium spp., enteropathogens of humans and other animals, are members of the Apicomplexa. In parasites belonging to this phylum, proteases have been shown to play a key role in the invasion of host cells, organelle biogenesis, and intracellular survival. The subtilases constitute a family of serine proteases present in prokaryotes, eukaryotes, and viruses. The C. parvum subtilase gene, CpSUB1, encodes a transcript of 3972 base pairs (bp) and 1324 amino acids. Using homologous polymerase chain reaction primers, a similar gene, ChSUB1, which has 98% (4007 bp/4050 bp) identity to CpSUB1, was found in C. hominis. The alignment of the CpSUB1 and ChSUB1 nucleotide sequences identified primarily silent substitutions, consistent with the absence of diversifying selection. The catalytic domain of CpSUB1 is very similar to that of other Apicomplexa (> 38% amino acid identity and >57% similarity) and to the bacterial subtilisin BPN from B. subtilis (36 and 47%). Transcriptional upregulation during merozoite development was observed in cell culture, and a predicted 76-bp intron located near the 3' end of the open reading frame was confirmed experimentally. Cryptosporidium parvum infection in cell culture was significantly inhibited by subtilisin inhibitor III and other serine protease inhibitors, emphasizing the importance of the parasite's subtilase for intracellular development and the enzyme's potential as a drug target.
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Affiliation(s)
- Xiaochuan Feng
- Division of Infectious Diseases, Tufts Cummings School of Veterinary Medicine, North Grafton, Massachusetts 01536, USA
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Doan LT, Martucci WE, Vargo MA, Atreya CE, Anderson KS. Nonconserved residues Ala287 and Ser290 of the Cryptosporidium hominis thymidylate synthase domain facilitate its rapid rate of catalysis. Biochemistry 2007; 46:8379-91. [PMID: 17580969 DOI: 10.1021/bi700531r] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Cryptosporidium hominis TS-DHFR exhibits an unusually high rate of catalysis at the TS domain, at least 10-fold greater than those of other TS enzymes. Using site-directed mutagenesis, we have mutated residues Ala287 and Ser290 in the folate-binding helix to phenylalanine and glycine, respectively, the corresponding residues in human and most other TS enzymes. Our results show that the mutant A287F, the mutant S290G, and the double mutant all have reduced affinities for methylene tetrahydrofolate and reduced rates of reaction at the TS domain. Interestingly, the S290G mutant enzyme had the lowest TS activity, with a catalytic efficiency approximately 200-fold lower than that of the wild type (WT). The rate of conformational change of the S290G mutant is approximately 80 times slower than that of WT, resulting in a change in the rate-limiting step from hydride transfer to covalent ternary complex formation. We have determined the crystal structure of ligand-bound S290G mutant enzyme, which shows that the primary effect of the mutation is an increase in the distance between the TS ligands. The kinetic and crystal structure data presented here provide the first evidence explaining the unusually fast TS rate in C. hominis.
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Affiliation(s)
- Lanxuan T Doan
- Department of Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, Connecticut 06520, USA
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Pelphrey PM, Popov VM, Joska TM, Beierlein JM, Bolstad ESD, Fillingham YA, Wright DL, Anderson AC. Highly Efficient Ligands for Dihydrofolate Reductase from Cryptosporidium hominis and Toxoplasma gondii Inspired by Structural Analysis. J Med Chem 2007; 50:940-50. [PMID: 17269758 DOI: 10.1021/jm061027h] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The search for effective therapeutics for cryptosporidiosis and toxoplasmosis has led to the discovery of novel inhibitors of dihydrofolate reductase (DHFR) that possess high ligand efficiency: compounds with high potency and low molecular weight. Detailed analysis of the crystal structure of dihydrofolate reductase-thymidylate synthase from Cryptosporidium hominis and a homology model of DHFR from Toxoplasma gondii inspired the synthesis of a new series of compounds with a propargyl-based linker between a substituted 2,4-diaminopyrimidine and a trimethoxyphenyl ring. An enantiomerically pure compound in this series exhibits IC50 values of 38 and 1 nM against C. hominis and T. gondii DHFR, respectively. Improvements of 368-fold or 5714-fold (C. hominis and T. gondii) relative to trimethoprim were generated by synthesizing just 14 new analogues and by adding only a total of 52 Da to the mass of the parent compound, creating an efficient ligand as an excellent candidate for further study.
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Affiliation(s)
- Phillip M Pelphrey
- Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, USA
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Wanyiri JW, O'Connor R, Allison G, Kim K, Kane A, Qiu J, Plaut AG, Ward HD. Proteolytic processing of the Cryptosporidium glycoprotein gp40/15 by human furin and by a parasite-derived furin-like protease activity. Infect Immun 2006; 75:184-92. [PMID: 17043102 PMCID: PMC1828422 DOI: 10.1128/iai.00944-06] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The apicomplexan parasite Cryptosporidium causes diarrheal disease worldwide. Proteolytic processing of proteins plays a significant role in host cell invasion by apicomplexan parasites. In previous studies, we described gp40/15, a Cryptosporidium sp. glycoprotein that is proteolytically cleaved to yield two surface glycopeptides (gp40 and gp15), which are implicated in mediating infection of host cells. In the present study, we showed that biosynthetically labeled gp40/15 is processed in Cryptosporidium parvum-infected HCT-8 cells. We identified a putative furin cleavage site RSRR downward arrow in the deduced amino acid sequence of gp40/15 from C. parvum and from all Cryptosporidium hominis subtypes except subtype 1e. Both human furin and a protease activity present in a C. parvum lysate cleaved recombinant C. parvum gp40/15 protein into 2 peptides, identified as gp40 and gp15 by size and by immunoreactivity with specific antibodies. C. hominis gp40/15 subtype 1e, in which the RSRR sequence is replaced by ISKR, has an alternative furin cleavage site (KSISKR downward arrow) and was also cleaved by both furin and the C. parvum lysate. Site-directed mutagenesis of the C. parvum RSRR sequence to ASRR resulted in inhibition of cleavage by furin and the C. parvum lysate. Cleavage of recombinant gp40/15 and a synthetic furin substrate by the C. parvum lysate was inhibited by serine protease inhibitors, by the specific furin inhibitor decanoyl-Arg-Val-Lys-Arg-chloromethylketone (Dec-RVKR-cmk), and by calcium chelators, suggesting that the parasite expresses a Ca2+ dependent, furin-like protease activity. The furin inhibitor Dec-RVKR-cmk decreased C. parvum infection of HCT-8 cells, suggesting that a furin-like protease activity may be involved in mediating host-parasite interactions.
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Affiliation(s)
- Jane W Wanyiri
- Division of Geographic Medicine and Infectious Diseases, Tufts-New England Medical Center, 750 Washington Street, Boston, MA 02111, USA
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Abstract
Mixed Cryptosporidium infections were detected in 7 of 21 patients with a diagnosis of rare Cryptosporidium canis or C. felis infections; 6 patients were infected with 2 Cryptosporidium spp. and 1 patient with 3 species. Mixed infections may occur more frequently than previously believed and should be considered when assessing cryptosporidiosis.
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Affiliation(s)
- Vitaliano Cama
- Centers for Disease Control and Prevention, Atlanta, Georgia, USA
- Johns Hopkins University, Baltimore, Maryland, USA
| | - Robert H. Gilman
- Johns Hopkins University, Baltimore, Maryland, USA
- Asociación Benéfica Proyectos en Informática, Salud, Medicina y Agricultura, Lima, Peru
| | | | | | - Ynes Ortega
- University of Georgia, Griffin, Georgia, USA
| | - Caryn Bern
- Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - Lihua Xiao
- Centers for Disease Control and Prevention, Atlanta, Georgia, USA
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Anderson AC. Two crystal structures of dihydrofolate reductase-thymidylate synthase from Cryptosporidium hominis reveal protein-ligand interactions including a structural basis for observed antifolate resistance. Acta Crystallogr Sect F Struct Biol Cryst Commun 2005; 61:258-62. [PMID: 16511011 PMCID: PMC1952288 DOI: 10.1107/s1744309105002435] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2004] [Accepted: 01/21/2005] [Indexed: 11/10/2022]
Abstract
Cryptosporidium hominis is a protozoan parasite that causes acute gastrointestinal illness. There are no effective therapies for cryptosporidiosis, highlighting the need for new drug-lead discovery. An analysis of the protein-ligand interactions in two crystal structures of dihydrofolate reductase-thymidylate synthase (DHFR-TS) from C. hominis, determined at 2.8 and 2.87 A resolution, reveals that the interactions of residues Ile29, Thr58 and Cys113 in the active site of C. hominis DHFR provide a possible structural basis for the observed antifolate resistance. A comparison with the structure of human DHFR reveals active-site differences that may be exploited for the design of species-selective inhibitors.
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Affiliation(s)
- Amy C Anderson
- Department of Chemistry, Dartmouth College, Hanover, NH 03755, USA.
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Xu P, Widmer G, Wang Y, Ozaki LS, Alves JM, Serrano MG, Puiu D, Manque P, Akiyoshi D, Mackey AJ, Pearson WR, Dear PH, Bankier AT, Peterson DL, Abrahamsen MS, Kapur V, Tzipori S, Buck GA. The genome of Cryptosporidium hominis. Nature 2004; 431:1107-12. [PMID: 15510150 DOI: 10.1038/nature02977] [Citation(s) in RCA: 385] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2004] [Accepted: 08/06/2004] [Indexed: 11/09/2022]
Abstract
Cryptosporidium species cause acute gastroenteritis and diarrhoea worldwide. They are members of the Apicomplexa--protozoan pathogens that invade host cells by using a specialized apical complex and are usually transmitted by an invertebrate vector or intermediate host. In contrast to other Apicomplexans, Cryptosporidium is transmitted by ingestion of oocysts and completes its life cycle in a single host. No therapy is available, and control focuses on eliminating oocysts in water supplies. Two species, C. hominis and C. parvum, which differ in host range, genotype and pathogenicity, are most relevant to humans. C. hominis is restricted to humans, whereas C. parvum also infects other mammals. Here we describe the eight-chromosome approximately 9.2-million-base genome of C. hominis. The complement of C. hominis protein-coding genes shows a striking concordance with the requirements imposed by the environmental niches the parasite inhabits. Energy metabolism is largely from glycolysis. Both aerobic and anaerobic metabolisms are available, the former requiring an alternative electron transport system in a simplified mitochondrion. Biosynthesis capabilities are limited, explaining an extensive array of transporters. Evidence of an apicoplast is absent, but genes associated with apical complex organelles are present. C. hominis and C. parvum exhibit very similar gene complements, and phenotypic differences between these parasites must be due to subtle sequence divergence.
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Affiliation(s)
- Ping Xu
- Center for the Study of Biological Complexity, Virginia Commonwealth University, Richmond, Virginia 23284-2030, USA
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Lilien RH, Bailey-Kellogg C, Anderson AC, Donald BR. A subgroup algorithm to identify cross-rotation peaks consistent with non-crystallographic symmetry. Acta Crystallogr D Biol Crystallogr 2004; 60:1057-67. [PMID: 15159565 DOI: 10.1107/s090744490400695x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2003] [Accepted: 03/24/2004] [Indexed: 11/10/2022]
Abstract
Molecular replacement (MR) often plays a prominent role in determining initial phase angles for structure determination by X-ray crystallography. In this paper, an efficient quaternion-based algorithm is presented for analyzing peaks from a cross-rotation function in order to identify model orientations consistent with proper non-crystallographic symmetry (NCS) and to generate proper NCS-consistent orientations missing from the list of cross-rotation peaks. The algorithm, CRANS, analyzes the rotation differences between each pair of cross-rotation peaks to identify finite subgroups. Sets of rotation differences satisfying the subgroup axioms correspond to orientations compatible with the correct proper NCS. The CRANS algorithm was first tested using cross-rotation peaks computed from structure-factor data for three test systems and was then used to assist in the de novo structure determination of dihydrofolate reductase-thymidylate synthase (DHFR-TS) from Cryptosporidium hominis. In every case, the CRANS algorithm runs in seconds to identify orientations consistent with the observed proper NCS and to generate missing orientations not present in the cross-rotation peak list. The CRANS algorithm has application in every molecular-replacement phasing effort with proper NCS.
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Affiliation(s)
- Ryan H Lilien
- Dartmouth Computer Science Department, Hanover, NH 03755, USA
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O'Neil RH, Lilien RH, Donald BR, Stroud RM, Anderson AC. The crystal structure of dihydrofolate reductase-thymidylate synthase from Cryptosporidium hominis reveals a novel architecture for the bifunctional enzyme. J Eukaryot Microbiol 2004; 50 Suppl:555-6. [PMID: 14736160 DOI: 10.1111/j.1550-7408.2003.tb00627.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Robert H O'Neil
- Department of Chemistry, Dartmouth College, Burke Laboratories, Hanover, NH 03755, USA
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O'Neil RH, Lilien RH, Donald BR, Stroud RM, Anderson AC. Phylogenetic classification of protozoa based on the structure of the linker domain in the bifunctional enzyme, dihydrofolate reductase-thymidylate synthase. J Biol Chem 2003; 278:52980-7. [PMID: 14555647 DOI: 10.1074/jbc.m310328200] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have determined the crystal structure of dihydrofolate reductase-thymidylate synthase (DHFR-TS) from Cryptosporidium hominis, revealing a unique linker domain containing an 11-residue alpha-helix that has extensive interactions with the opposite DHFR-TS monomer of the homodimeric enzyme. Analysis of the structure of DHFR-TS from C. hominis and of previously solved structures of DHFR-TS from Plasmodium falciparum and Leishmania major reveals that the linker domain primarily controls the relative orientation of the DHFR and TS domains. Using the tertiary structure of the linker domains, we have been able to place a number of protozoa in two distinct and dissimilar structural families corresponding to two evolutionary families and provide the first structural evidence validating the use of DHFR-TS as a tool of phylogenetic classification. Furthermore, the structure of C. hominis DHFR-TS calls into question surface electrostatic channeling as the universal means of dihydrofolate transport between TS and DHFR in the bifunctional enzyme.
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Affiliation(s)
- Robert H O'Neil
- Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, USA
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Iturriaga R, Zhang S, Sonek GJ, Stibbs H. Detection of respiratory enzyme activity in Giardia cysts and Cryptosporidium oocysts using redox dyes and immunofluorescence techniques. J Microbiol Methods 2001; 46:19-28. [PMID: 11412910 DOI: 10.1016/s0167-7012(01)00249-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
The fluorescent redox dye 5-cyano-2,3-ditolyl tetrazolium chloride (CTC), combined with fluorescein-labeled antibodies, was tested for the simultaneous detection of the respiratory electron transport system (ETS) activity and enumeration of Giardia cysts and Cryptosporidium oocysts by spectral microfluorometry and epifluorescence microscopy. The reduction of CTC and p-iodonitrotetrazolium violet (INT), a non-fluorescent redox dye, was compared with propidium iodide (PI) and fluorescein diacetate (FDA) for the measurements of Giardia cyst viability over time. According to the PI and FDA staining techniques, nearly 60% of the cysts tested viable at the beginning of the observations; after 21 days their viability decreased to 5%. The redox dyes indicated that approximately 4-10% of the cysts were metabolically active 48 h after they were shed, followed by a decline in enzyme activity to near undetectable levels after 4 days. Spectral analysis on individual cysts indicated that the fluorescence emission of the reduced CTC and the fluorescein-labeled antibodies is distinctive for each compound and suitable for their simultaneous determination by microphotometry, flow cytometry and epifluorescence microscopy. The fluorescence signal remained without alteration when the cysts were transferred onto microscope slides coated with an optical embedding medium and stored at -20 degrees C. The fluorescence intensity of the reduced CTC, when properly standardized, can provide quantitative measurements of ETS activity of the cysts. This is the first report of a method to determine enzyme redox activity on intact cysts applicable to water, laboratory and animal samples.
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Affiliation(s)
- R Iturriaga
- Department of Biological Sciences, University of Southern California, 90089-0371, Los Angeles, CA, USA.
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Abstract
Soluble extracts of the oocysts of Cryptosporidium parvum had demonstrable, but low, activities of malate dehydrogenase (MDH, EC. 1.1.1.37), carboxylesterase (ES, EC 3.1.1.1) and lactate dehydrogenase (LDH, EC. 1.1.1.27) following thin-layer starch-gel electrophoresis. Much higher activities of glucose phosphate isomerase (GPI, EC. 5.3.1.9) and phosphoglucomutase (PGM, EC. 2.7.5.1) were found, and zymograms of these two enzymes were used to characterise isolates of C. parvum from human, bovine, ovine and cervine sources, C. muris from the brown rat and C. baileyi from young turkeys. PGM and GPI zymograms clearly distinguished between C. parvum, C. muris and C. baileyi. The five isolates of C. parvum showed the same electrophoretic mobility for GPI, whereas the PGM mobility of the single human isolate of C. parvum examined was clearly different from that of the other isolates. This is the first report of the use of isoenzymes to distinguish between species and isolates of Cryptosporidium.
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Affiliation(s)
- B W Ogunkolade
- Department of Clinical Sciences, London School of Hygiene and Tropical Medicine, UK
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