4RHJ

Crystal structure of wild-type T. brucei arginase-like protein in a reduced form

Summary for 4RHJ

• Entry DOI: 10.2210/pdb4rhj/pdb
• Related: 4RHI 4RHK 4RHL 4RHM 4RHQ
• Descriptor: Arginase, 1,2-ETHANEDIOL (3 entities in total)
• Functional Keywords: arginase-deacetylase fold, unknown function
• Biological source: Trypanosoma brucei brucei
• Total number of polymer chains: 6
• Total formula weight: 232641.77

Authors

Hai, Y.,Barrett, M.P.,Christianson, D.W. (deposition date: 2014-10-02, release date: 2014-12-31, Last modification date: 2023-09-20)

Primary citation

Hai, Y.,Kerkhoven, E.J.,Barrett, M.P.,Christianson, D.W.
Crystal Structure of an Arginase-like Protein from Trypanosoma brucei That Evolved without a Binuclear Manganese Cluster.
Biochemistry, 54:458-471, 2015

PubMed Abstract: The X-ray crystal structure of an arginase-like protein from the parasitic protozoan Trypanosoma brucei, designated TbARG, is reported at 1.80 and 2.38 Å resolution in its reduced and oxidized forms, respectively. The oxidized form of TbARG is a disulfide-linked hexamer that retains the overall architecture of a dimer of trimers in the reduced form. Intriguingly, TbARG does not contain metal ions in its putative active site, and amino acid sequence comparisons indicate that all but one of the residues required for coordination to the catalytically obligatory binuclear manganese cluster in other arginases are substituted here with residues incapable of metal ion coordination. Therefore, the structure of TbARG is the first of a member of the arginase/deacetylase superfamily that is not a metalloprotein. Although we show that metal binding activity is easily reconstituted in TbARG by site-directed mutagenesis and confirmed in X-ray crystal structures, it is curious that this protein and its parasitic orthologues evolved away from metal binding function. Knockout of the TbARG gene from the genome demonstrated that its function is not essential to cultured bloodstream-form T. brucei, and metabolomics analysis confirmed that the enzyme has no role in the conversion of l-arginine to l-ornithine in these cells. While the molecular function of TbARG remains enigmatic, the fact that the T. brucei genome encodes only this protein and not a functional arginase indicates that the parasite must import l-ornithine from its host to provide a source of substrate for ornithine decarboxylase in the polyamine biosynthetic pathway, an active target for the development of antiparasitic drugs.

PubMed: 25536859
DOI: 10.1021/bi501366a

Experimental method

X-RAY DIFFRACTION (1.8 Å)