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Functional Characterization and Structure-Guided Mutational Analysis of the Transsulfuration Enzyme Cystathionine γ-Lyase from Toxoplasma gondii
Sulfur-containing amino acids play essential roles in many organisms. The protozoan parasite Toxoplasma gondii includes the genes for cystathionine β-synthase and cystathionine γ-lyase (TgCGL), as well as for cysteine synthase, which are crucial enzymes of the transsulfuration and de novo pathways f...
Autores principales: | , , , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
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MDPI
2018
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6073527/ https://www.ncbi.nlm.nih.gov/pubmed/30036991 http://dx.doi.org/10.3390/ijms19072111 |
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author | Maresi, Elena Janson, Giacomo Fruncillo, Silvia Paiardini, Alessandro Vallone, Rosario Dominici, Paola Astegno, Alessandra |
author_facet | Maresi, Elena Janson, Giacomo Fruncillo, Silvia Paiardini, Alessandro Vallone, Rosario Dominici, Paola Astegno, Alessandra |
author_sort | Maresi, Elena |
collection | PubMed |
description | Sulfur-containing amino acids play essential roles in many organisms. The protozoan parasite Toxoplasma gondii includes the genes for cystathionine β-synthase and cystathionine γ-lyase (TgCGL), as well as for cysteine synthase, which are crucial enzymes of the transsulfuration and de novo pathways for cysteine biosynthesis, respectively. These enzymes are specifically expressed in the oocyst stage of T. gondii. However, their functionality has not been investigated. Herein, we expressed and characterized the putative CGL from T. gondii. Recombinant TgCGL almost exclusively catalyses the α,γ-hydrolysis of l-cystathionine to form l-cysteine and displays marginal reactivity toward l-cysteine. Structure-guided homology modelling revealed two striking amino acid differences between the human and parasite CGL active-sites (Glu59 and Ser340 in human to Ser77 and Asn360 in toxoplasma). Mutation of Asn360 to Ser demonstrated the importance of this residue in modulating the specificity for the catalysis of α,β- versus α,γ-elimination of l-cystathionine. Replacement of Ser77 by Glu completely abolished activity towards l-cystathionine. Our results suggest that CGL is an important functional enzyme in T. gondii, likely implying that the reverse transsulfuration pathway is operative in the parasite; we also probed the roles of active-site architecture and substrate binding conformations as determinants of reaction specificity in transsulfuration enzymes. |
format | Online Article Text |
id | pubmed-6073527 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2018 |
publisher | MDPI |
record_format | MEDLINE/PubMed |
spelling | pubmed-60735272018-08-13 Functional Characterization and Structure-Guided Mutational Analysis of the Transsulfuration Enzyme Cystathionine γ-Lyase from Toxoplasma gondii Maresi, Elena Janson, Giacomo Fruncillo, Silvia Paiardini, Alessandro Vallone, Rosario Dominici, Paola Astegno, Alessandra Int J Mol Sci Article Sulfur-containing amino acids play essential roles in many organisms. The protozoan parasite Toxoplasma gondii includes the genes for cystathionine β-synthase and cystathionine γ-lyase (TgCGL), as well as for cysteine synthase, which are crucial enzymes of the transsulfuration and de novo pathways for cysteine biosynthesis, respectively. These enzymes are specifically expressed in the oocyst stage of T. gondii. However, their functionality has not been investigated. Herein, we expressed and characterized the putative CGL from T. gondii. Recombinant TgCGL almost exclusively catalyses the α,γ-hydrolysis of l-cystathionine to form l-cysteine and displays marginal reactivity toward l-cysteine. Structure-guided homology modelling revealed two striking amino acid differences between the human and parasite CGL active-sites (Glu59 and Ser340 in human to Ser77 and Asn360 in toxoplasma). Mutation of Asn360 to Ser demonstrated the importance of this residue in modulating the specificity for the catalysis of α,β- versus α,γ-elimination of l-cystathionine. Replacement of Ser77 by Glu completely abolished activity towards l-cystathionine. Our results suggest that CGL is an important functional enzyme in T. gondii, likely implying that the reverse transsulfuration pathway is operative in the parasite; we also probed the roles of active-site architecture and substrate binding conformations as determinants of reaction specificity in transsulfuration enzymes. MDPI 2018-07-20 /pmc/articles/PMC6073527/ /pubmed/30036991 http://dx.doi.org/10.3390/ijms19072111 Text en © 2018 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). |
spellingShingle | Article Maresi, Elena Janson, Giacomo Fruncillo, Silvia Paiardini, Alessandro Vallone, Rosario Dominici, Paola Astegno, Alessandra Functional Characterization and Structure-Guided Mutational Analysis of the Transsulfuration Enzyme Cystathionine γ-Lyase from Toxoplasma gondii |
title | Functional Characterization and Structure-Guided Mutational Analysis of the Transsulfuration Enzyme Cystathionine γ-Lyase from Toxoplasma gondii |
title_full | Functional Characterization and Structure-Guided Mutational Analysis of the Transsulfuration Enzyme Cystathionine γ-Lyase from Toxoplasma gondii |
title_fullStr | Functional Characterization and Structure-Guided Mutational Analysis of the Transsulfuration Enzyme Cystathionine γ-Lyase from Toxoplasma gondii |
title_full_unstemmed | Functional Characterization and Structure-Guided Mutational Analysis of the Transsulfuration Enzyme Cystathionine γ-Lyase from Toxoplasma gondii |
title_short | Functional Characterization and Structure-Guided Mutational Analysis of the Transsulfuration Enzyme Cystathionine γ-Lyase from Toxoplasma gondii |
title_sort | functional characterization and structure-guided mutational analysis of the transsulfuration enzyme cystathionine γ-lyase from toxoplasma gondii |
topic | Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6073527/ https://www.ncbi.nlm.nih.gov/pubmed/30036991 http://dx.doi.org/10.3390/ijms19072111 |
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