3NTJ: Redox Regulation Of Plasmodium Falciparum Ornithine Delta- Aminotransferase

Citation:
Abstract
Ornithine delta-aminotransferase (OAT) of the malaria parasite Plasmodium falciparum catalyzes the reversible conversion of ornithine into glutamate-5-semialdehyde and glutamate and is-in contrast to its human counterpart-activated by thioredoxin (Trx) by a factor of 10. Trx, glutaredoxin, and plasmoredoxin are redox-active proteins that play a crucial role in the maintenance and control of redox reactions, and were shown to interact with P. falciparum OAT. OAT, which is involved in ornithine homeostasis and proline biosynthesis, is essential for mitotic cell division in rapidly growing cells, thus representing a potential target for chemotherapeutic intervention. Here we report the three-dimensional crystal structure of P. falciparum OAT at 2.3 A resolution. The overall structure is very similar to that of the human OAT. However, in plasmodial OAT, the loop involved in substrate binding contains two cysteine residues, which are lacking in human OAT. Site-directed mutagenesis of these cysteines and functional analysis demonstrated that Cys154 and Cys163 mediate the interaction with Trx. Interestingly, the Cys154-->Ser mutant has a strongly reduced specific activity, most likely due to impaired binding of ornithine. Cys154 and Cys163 are highly conserved in Plasmodium but do not exist in other organisms, suggesting that redox regulation of OAT by Trx is specific for malaria parasites. Plasmodium might require a tight Trx-mediated control of OAT activity for coordinating ornithine homeostasis, polyamine synthesis, proline synthesis, and mitotic cell division.
PDB ID: 3NTJDownload
MMDB ID: 83875
PDB Deposition Date: 2010/7/5
Updated in MMDB: 2012/11
Experimental Method:
x-ray diffraction
Resolution: 3  Å
Source Organism:
Similar Structures:
Biological Unit for 3NTJ: dimeric; determined by author and by software (PISA)
Molecular Components in 3NTJ
Label Count Molecule
Proteins (2 molecules)
2
Ornithine Aminotransferase(Gene symbol: PF3D7_0608800)
Molecule annotation
Chemicals (2 molecules)
1
2
* Click molecule labels to explore molecular sequence information.

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