title: Direct evidence for cyanide-insensitive quinol oxidase (alternative oxidase) in apicomplexan parasite Cryptosporidium parvum: phylogenetic and therapeutic implications.
abstract: Cryptosporidium parvum is a parasitic protozoan that causes the diarrheal disease cryptosporidiosis, for which no satisfactory chemotherapy is currently available. Although the presence of mitochondria in this parasite has been suggested, its respiratory system is poorly understood due to difficulties in performing biochemical analyses. In order to better understand the respiratory chain of C. parvum, we surveyed its genomic DNA database in GenBank and identified a partial sequence encoding cyanide-insensitive alternative oxidase (AOX). Based on this sequence, we cloned C. parvum AOX (CpAOX) cDNA from the phylum apicomplexa for the first time. The deduced amino acid sequence (335 a.a.) of CpAOX contains diiron coordination motifs (-E-, -EXXH-) that are conserved among AOXs. Phylogenetic analysis suggested that CpAOX is a mitochondrial-type AOX, possibly derived from mitochondrial endosymbiont gene transfer. The recombinant enzyme expressed in Escherichia coli showed quinol oxidase activity. This activity was insensitive to cyanide and highly sensitive to ascofuranone, a specific inhibitor of trypanosome AOX.
authors.affiliation: Department of Molecular Parasitology, Nagoya City University, Graduate School of Medical Sciences, Nagoya 467-8601, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Suzuki
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Hashimoto
authors.forename: Yoshisada
authors.initials: Y
authors.lastname: Yabu
authors.forename: Yasutoshi
authors.initials: Y
authors.lastname: Kido
authors.forename: Kimitoshi
authors.initials: K
authors.lastname: Sakamoto
authors.forename: Coh-ichi
authors.initials: C
authors.lastname: Nihei
authors.forename: Mariko
authors.initials: M
authors.lastname: Hato
authors.forename: Shu-ichi
authors.initials: S
authors.lastname: Suzuki
authors.forename: Yuko
authors.initials: Y
authors.lastname: Amano
authors.forename: Kazuo
authors.initials: K
authors.lastname: Nagai
authors.forename: Tomoyoshi
authors.initials: T
authors.lastname: Hosokawa
authors.forename: Nobuko
authors.initials: N
authors.lastname: Minagawa
authors.forename: Nobuo
authors.initials: N
authors.lastname: Ohta
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Kita
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D003457:Cryptosporidiosis / Q000188:drug therapy; D016785:Cryptosporidium parvum / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D016054:DNA, Protozoan / Q000235:genetics; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D008928:Mitochondria / Q000201:enzymology; D008969:Molecular Sequence Data; D010088:Oxidoreductases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012717:Sesquiterpenes / Q000494:pharmacology
chemical_list: D016054:DNA, Protozoan; D004791:Enzyme Inhibitors; D011994:Recombinant Proteins; D012717:Sesquiterpenes; D010088:Oxidoreductases; C020094:duroquinol oxidase; C006640:ascofuranone