RESUMEN

The Arabidopsis thaliana flavoprotein AtHAL3a is related to plant growth and salt and osmotic tolerance. AtHAL3a shows sequence homology to the bacterial flavoproteins EpiD and Dfp. EpiD, Dfp, and AtHAL3a are members of the homo-oligomeric flavin-containing Cys decarboxylase (HFCD) protein family. We demonstrate that AtHAL3a catalyzes the decarboxylation of (R)-4'-phospho-N-pantothenoylcysteine to 4'-phosphopantetheine. This key step in coenzyme A biosynthesis is catalyzed in bacteria by the Dfp proteins. Exchange of His-90 of AtHAL3a for Asn led to complete inactivation of the enzyme. Dfp and AtHAL3a are characterized by a shortened substrate binding clamp compared with EpiD. Exchange of the cysteine residue of the conserved ACGD motif of this binding clamp resulted in loss of (R)-4'-phospho-N-pantothenoylcysteine decarboxylase activity. Based on the crystal structures of EpiD H67N with bound substrate peptide and of AtHAL3a, we present a model for the binding of (R)-4'-phospho-N-pantothenoylcysteine to AtHAL3a.

Asunto(s)

Proteínas de Arabidopsis , Arabidopsis/química , Coenzima A/biosíntesis , Cisteína/metabolismo , Panteteína/análogos & derivados , Panteteína/metabolismo , Ácido Pantoténico/metabolismo , Proteínas de Plantas/química , Proteínas de Plantas/metabolismo , Secuencia de Aminoácidos , Sitios de Unión , Carboxiliasas/química , Catálisis , Cromatografía en Gel , Cristalografía por Rayos X , Cisteína/análogos & derivados , Cisteína/química , Electroforesis en Gel de Poliacrilamida , Immunoblotting , Modelos Químicos , Modelos Moleculares , Datos de Secuencia Molecular , Complejos Multienzimáticos/química , Mutagénesis Sitio-Dirigida , Mutación , Oxidorreductasas/química , Ácido Pantoténico/análogos & derivados , Péptido Sintasas/química , Reacción en Cadena de la Polimerasa , Unión Proteica , Conformación Proteica , Sales (Química)/metabolismo , Homología de Secuencia de Aminoácido , Transducción de Señal , Factores de Tiempo