Structural Analysis of an <sc>l</sc>-Cysteine Desulfurase from an Ssp DNA Phosphorothioation System

ABSTRACT DNA phosphorothioate (PT) modification, in which the nonbridging oxygen in the sugar-phosphate backbone is substituted by sulfur, is catalyzed by DndABCDE or SspABCD in a double-stranded or single-stranded manner, respectively. In Dnd and Ssp systems, mobilization of sulfur in PT formation...

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Autores principales: Liqiong Liu, Susu Jiang, Mai Xing, Chao Chen, Chongde Lai, Na Li, Guangfeng Liu, Dan Wu, Haiyan Gao, Liang Hong, Pan Tan, Shi Chen, Zixin Deng, Geng Wu, Lianrong Wang
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Publicado: American Society for Microbiology 2020
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spelling oai:doaj.org-article:a4524d2bcfab4ea9beee2f3b7c957a5e2021-11-15T15:57:03ZStructural Analysis of an <sc>l</sc>-Cysteine Desulfurase from an Ssp DNA Phosphorothioation System10.1128/mBio.00488-202150-7511https://doaj.org/article/a4524d2bcfab4ea9beee2f3b7c957a5e2020-04-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.00488-20https://doaj.org/toc/2150-7511ABSTRACT DNA phosphorothioate (PT) modification, in which the nonbridging oxygen in the sugar-phosphate backbone is substituted by sulfur, is catalyzed by DndABCDE or SspABCD in a double-stranded or single-stranded manner, respectively. In Dnd and Ssp systems, mobilization of sulfur in PT formation starts with the activation of the sulfur atom of cysteine catalyzed by the DndA and SspA cysteine desulfurases, respectively. Despite playing the same biochemical role, SspA cannot be functionally replaced by DndA, indicating its unique physiological properties. In this study, we solved the crystal structure of Vibrio cyclitrophicus SspA in complex with its natural substrate, cysteine, and cofactor, pyridoxal phosphate (PLP), at a resolution of 1.80 Å. Our solved structure revealed the molecular mechanism that SspA employs to recognize its cysteine substrate and PLP cofactor, suggesting a common binding mode shared by cysteine desulfurases. In addition, although the distance between the catalytic Cys314 and the substrate cysteine is 8.9 Å, which is too far for direct interaction, our structural modeling and biochemical analysis revealed a conformational change in the active site region toward the cysteine substrate to move them close to each other to facilitate the nucleophilic attack. Finally, the pulldown analysis showed that SspA could form a complex with SspD, an ATP pyrophosphatase, suggesting that SspD might potentially accept the activated sulfur atom directly from SspA, providing further insights into the biochemical pathway of Ssp-mediated PT modification. IMPORTANCE Apart from its roles in Fe-S cluster assembly, tRNA thiolation, and sulfur-containing cofactor biosynthesis, cysteine desulfurase serves as a sulfur donor in the DNA PT modification, in which a sulfur atom substitutes a nonbridging oxygen in the DNA phosphodiester backbone. The initial sulfur mobilization from l-cysteine is catalyzed by the SspA cysteine desulfurase in the SspABCD-mediated DNA PT modification system. By determining the crystal structure of SspA, the study presents the molecular mechanism that SspA employs to recognize its cysteine substrate and PLP cofactor. To overcome the long distance (8.9 Å) between the catalytic Cys314 and the cysteine substrate, a conformational change occurs to bring Cys314 to the vicinity of the substrate, allowing for nucleophilic attack.Liqiong LiuSusu JiangMai XingChao ChenChongde LaiNa LiGuangfeng LiuDan WuHaiyan GaoLiang HongPan TanShi ChenZixin DengGeng WuLianrong WangAmerican Society for MicrobiologyarticleDNA PT modificationSsp systemcysteine desulfurasecrystal structureMicrobiologyQR1-502ENmBio, Vol 11, Iss 2 (2020)
institution DOAJ
collection DOAJ
language EN
topic DNA PT modification
Ssp system
cysteine desulfurase
crystal structure
Microbiology
QR1-502
spellingShingle DNA PT modification
Ssp system
cysteine desulfurase
crystal structure
Microbiology
QR1-502
Liqiong Liu
Susu Jiang
Mai Xing
Chao Chen
Chongde Lai
Na Li
Guangfeng Liu
Dan Wu
Haiyan Gao
Liang Hong
Pan Tan
Shi Chen
Zixin Deng
Geng Wu
Lianrong Wang
Structural Analysis of an <sc>l</sc>-Cysteine Desulfurase from an Ssp DNA Phosphorothioation System
description ABSTRACT DNA phosphorothioate (PT) modification, in which the nonbridging oxygen in the sugar-phosphate backbone is substituted by sulfur, is catalyzed by DndABCDE or SspABCD in a double-stranded or single-stranded manner, respectively. In Dnd and Ssp systems, mobilization of sulfur in PT formation starts with the activation of the sulfur atom of cysteine catalyzed by the DndA and SspA cysteine desulfurases, respectively. Despite playing the same biochemical role, SspA cannot be functionally replaced by DndA, indicating its unique physiological properties. In this study, we solved the crystal structure of Vibrio cyclitrophicus SspA in complex with its natural substrate, cysteine, and cofactor, pyridoxal phosphate (PLP), at a resolution of 1.80 Å. Our solved structure revealed the molecular mechanism that SspA employs to recognize its cysteine substrate and PLP cofactor, suggesting a common binding mode shared by cysteine desulfurases. In addition, although the distance between the catalytic Cys314 and the substrate cysteine is 8.9 Å, which is too far for direct interaction, our structural modeling and biochemical analysis revealed a conformational change in the active site region toward the cysteine substrate to move them close to each other to facilitate the nucleophilic attack. Finally, the pulldown analysis showed that SspA could form a complex with SspD, an ATP pyrophosphatase, suggesting that SspD might potentially accept the activated sulfur atom directly from SspA, providing further insights into the biochemical pathway of Ssp-mediated PT modification. IMPORTANCE Apart from its roles in Fe-S cluster assembly, tRNA thiolation, and sulfur-containing cofactor biosynthesis, cysteine desulfurase serves as a sulfur donor in the DNA PT modification, in which a sulfur atom substitutes a nonbridging oxygen in the DNA phosphodiester backbone. The initial sulfur mobilization from l-cysteine is catalyzed by the SspA cysteine desulfurase in the SspABCD-mediated DNA PT modification system. By determining the crystal structure of SspA, the study presents the molecular mechanism that SspA employs to recognize its cysteine substrate and PLP cofactor. To overcome the long distance (8.9 Å) between the catalytic Cys314 and the cysteine substrate, a conformational change occurs to bring Cys314 to the vicinity of the substrate, allowing for nucleophilic attack.
format article
author Liqiong Liu
Susu Jiang
Mai Xing
Chao Chen
Chongde Lai
Na Li
Guangfeng Liu
Dan Wu
Haiyan Gao
Liang Hong
Pan Tan
Shi Chen
Zixin Deng
Geng Wu
Lianrong Wang
author_facet Liqiong Liu
Susu Jiang
Mai Xing
Chao Chen
Chongde Lai
Na Li
Guangfeng Liu
Dan Wu
Haiyan Gao
Liang Hong
Pan Tan
Shi Chen
Zixin Deng
Geng Wu
Lianrong Wang
author_sort Liqiong Liu
title Structural Analysis of an <sc>l</sc>-Cysteine Desulfurase from an Ssp DNA Phosphorothioation System
title_short Structural Analysis of an <sc>l</sc>-Cysteine Desulfurase from an Ssp DNA Phosphorothioation System
title_full Structural Analysis of an <sc>l</sc>-Cysteine Desulfurase from an Ssp DNA Phosphorothioation System
title_fullStr Structural Analysis of an <sc>l</sc>-Cysteine Desulfurase from an Ssp DNA Phosphorothioation System
title_full_unstemmed Structural Analysis of an <sc>l</sc>-Cysteine Desulfurase from an Ssp DNA Phosphorothioation System
title_sort structural analysis of an <sc>l</sc>-cysteine desulfurase from an ssp dna phosphorothioation system
publisher American Society for Microbiology
publishDate 2020
url https://doaj.org/article/a4524d2bcfab4ea9beee2f3b7c957a5e
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