Localisation of Plasmodium falciparum
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- 作者：Viswanathan Arun Nagaraj ; Rajavel Arumugam ; Nagasuma R. Ch ; ra ; Dasari Prasad ; Pundi N. Rangarajan ; Govindarajan Padmanaban
- 关键词：Uroporphyrinogen decarboxylase ; Heme ; Plasmodium falciparum ; Apicoplast ; Catalytic efficiency ; Weak dimer
- 刊名：International Journal for Parasitology
- 出版年：2009
- 出版时间：April 2009
- 年：2009
- 卷：39
- 期：5
- 页码：559-568
- 全文大小：943 K
文摘
Uroporphyrinogen decarboxylase (UROD) is a key enzyme in the heme-biosynthetic pathway and in Plasmodium falciparum it occupies a strategic position in the proposed hybrid pathway for heme biosynthesis involving shuttling of intermediates between different subcellular compartments in the parasite. In the present study, we demonstrate that an N-terminally truncated recombinant P. falciparum UROD (r(Δ)PfUROD) over-expressed and purified from Escherichia coli cells, as well as the native enzyme from the parasite were catalytically less efficient compared with the host enzyme, although they were similar in other enzyme parameters. Molecular modeling of PfUROD based on the known crystal structure of the human enzyme indicated that the protein manifests a distorted triose phosphate isomerase (TIM) barrel fold which is conserved in all the known structures of UROD. The parasite enzyme shares all the conserved or invariant amino acid residues at the active and substrate binding sites, but is rich in lysine residues compared with the host enzyme. Mutation of specific lysine residues corresponding to residues at the dimer interface in human UROD enhanced the catalytic efficiency of the enzyme and dimer stability indicating that the lysine rich nature and weak dimer interface of the wild-type PfUROD could be responsible for its low catalytic efficiency. PfUROD was localised to the apicoplast, indicating the requirement of additional mechanisms for transport of the product coproporphyrinogen to other subcellular sites for its further conversion and ultimate heme formation.