1mvl
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PPC decarboxylase mutant C175S
OverviewOverview
The Arabidopsis thaliana protein AtHAL3a decarboxylates 4'-phosphopantothenoylcysteine to 4'-phosphopantetheine, a step in coenzyme A biosynthesis. Surprisingly, this decarboxylation reaction is carried out as an FMN-dependent redox reaction. In the first half-reaction, the side-chain of the cysteine residue of 4'-phosphopantothenoylcysteine is oxidised and the thioaldehyde intermediate decarboxylates spontaneously to the 4'-phosphopantothenoyl-aminoethenethiol intermediate. In the second half-reaction this compound is reduced to 4'-phosphopantetheine and the FMNH(2) cofactor is re-oxidised. The active site mutant C175S is unable to perform this reductive half-reaction. Here, we present the crystal structure of the AtHAL3a mutant C175S in complex with the reaction intermediate pantothenoyl-aminoethenethiol and FMNH(2). The geometry of binding suggests that reduction of the C(alpha)=C(beta) double bond of the intermediate can be performed by direct hydride-transfer from N5 of FMNH(2) to C(beta) of the aminoethenethiol-moiety supported by a protonation of C(alpha) by Cys175. The binding mode of the substrate is very similar to that previously observed for a pentapeptide to the homologous enzyme EpiD that introduces the aminoethenethiol-moiety as final reaction product at the C terminus of peptidyl-cysteine residues. This finding further supports our view that these homologous enzymes form a protein family of homo-oligomeric flavin-containing cysteine decarboxylases, which we have termed HFCD family.
About this StructureAbout this Structure
1MVL is a Single protein structure of sequence from Arabidopsis thaliana with as ligand. Active as Phosphopantothenoylcysteine decarboxylase, with EC number 4.1.1.36 Full crystallographic information is available from OCA.
ReferenceReference
Crystal structure of the plant PPC decarboxylase AtHAL3a complexed with an ene-thiol reaction intermediate., Steinbacher S, Hernandez-Acosta P, Bieseler B, Blaesse M, Huber R, Culianez-Macia FA, Kupke T, J Mol Biol. 2003 Mar 14;327(1):193-202. PMID:12614618
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