Allosterically gated enzyme dynamics in the cysteine synthase complex regulate cysteine biosynthesis in Arabidopsis thaliana.
Structure
; 20(2): 292-302, 2012 Feb 08.
Article
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| MEDLINE
| ID: mdl-22325778
ABSTRACT
Plants and bacteria assimilate sulfur into cysteine. Cysteine biosynthesis involves a bienzyme complex, the cysteine synthase complex (CSC), which consists of serine-acetyl-transferase (SAT) and O-acetyl-serine-(thiol)-lyase (OAS-TL) enzymes. The activity of OAS-TL is reduced by formation of the CSC. Although this reduction is an inherent part of the self-regulation cycle of cysteine biosynthesis, there has until now been no explanation as to how OAS-TL loses activity in plants. Complexation of SAT and OAS-TL involves binding of the C-terminal tail of SAT in one of the active sites of the homodimeric OAS-TL. We here explore the flexibility of the unoccupied active site in Arabidopsis thaliana cytosolic and mitochondrial OAS-TLs. Our results reveal two gates in the OAS-TL active site that define its accessibility. The observed dynamics of the gates show allosteric closure of the unoccupied active site of OAS-TL in the CSC, which can hinder substrate binding, abolishing its turnover to cysteine.
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1
Base de datos:
MEDLINE
Asunto principal:
Arabidopsis
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Cisteína
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Cisteína Sintasa
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Proteínas de Arabidopsis
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Mitocondrias
Idioma:
En
Revista:
Structure
Asunto de la revista:
BIOLOGIA MOLECULAR
/
BIOQUIMICA
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BIOTECNOLOGIA
Año:
2012
Tipo del documento:
Article