1mvn
PPC decarboxylase mutant C175S complexed with pantothenoylaminoethenethiol
Structural highlights
FunctionHAL3A_ARATH Involved in plant growth and salt and osmotic tolerance. Catalyzes the decarboxylation of 4'-phosphopantothenoylcysteine to 4'-phosphopantetheine, a key step in coenzyme A biosynthesis. The enzyme is also able to decarboxylate pantothenoylcysteine to pantothenoylcysteamine.[1] [2] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe 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. 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[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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