Abstract
Thiolases are essential CoA-dependent enzymes in lipid metabolism. In the present study we report the crystal structures of trypanosomal and leishmanial SCP2 (sterol carrier protein, type-2)-thiolases. Trypanosomatidae cause various widespread devastating (sub)-tropical diseases, for which adequate treatment is lacking. The structures reveal the unique geometry of the active site of this poorly characterized subfamily of thiolases. The key catalytic residues of the classical thiolases are two cysteine residues, functioning as a nucleophile and an acid/base respectively. The latter cysteine residue is part of a CxG motif. Interestingly, this cysteine residue is not conserved in SCP2-thiolases. The structural comparisons now show that in SCP2-thiolases the catalytic acid/base is provided by the cysteine residue of the HDCF motif, which is unique for this thiolase subfamily. This HDCF cysteine residue is spatially equivalent to the CxG cysteine residue of classical thiolases. The HDCF cysteine residue is activated for acid/base catalysis by two main chain NH-atoms, instead of two water molecules, as present in the CxG active site. The structural results have been complemented with enzyme activity data, confirming the importance of the HDCF cysteine residue for catalysis. The data obtained suggest that these trypanosomatid SCP2-thiolases are biosynthetic thiolases. These findings provide promise for drug discovery as biosynthetic thiolases catalyse the first step of the sterol biosynthesis pathway that is essential in several of these parasites.
Original language | English |
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Pages (from-to) | 119-130 |
Number of pages | 12 |
Journal | The Biochemical journal |
Volume | 455 |
Issue number | 1 |
Early online date | 2 Aug 2013 |
DOIs | |
Publication status | Published - 1 Oct 2013 |
Keywords
- Amino Acid Motifs
- Biocatalysis
- Carrier Proteins/chemistry
- Catalytic Domain
- Coenzyme A/chemistry
- Crystallography, X-Ray
- Cysteine/chemistry
- Escherichia coli/genetics
- Leishmania mexicana/chemistry
- Models, Molecular
- Molecular Sequence Data
- Protein Binding
- Protein Structure, Quaternary
- Protein Structure, Secondary
- Protein Structure, Tertiary
- Protozoan Proteins/chemistry
- Recombinant Proteins/chemistry
- Sequence Alignment
- Sequence Homology, Amino Acid
- Trypanosoma brucei brucei/chemistry
- coenzyme A (CoA)
- lipid metabolism
- oxyanion hole
- sterol biosynthesis
- thioster chemistry