Biochemical and molecular characterization of nucleoside triphosphate hydrolase isozymes from the parasitic protozoan Toxoplasma gondii

T. Asai, S. Miura, L. D. Sibley, H. Okabayashi, T. Takeuchi

研究成果: Article査読

169 被引用数 (Scopus)

抄録

We have previously reported the presence of a novel nucleoside triphosphate hydrolase (NTPase) in the rapidly multiplying tachyzoite form of a virulent strain (RH) of Toxoplasma gondii. On further examination, it was found that the purified enzyme was not a single enzyme but was a mixture of two isozymes termed NTPase-I and NTPase-II. The two isozymes had similar molecular masses of approximately 240-270 kDa by gel filtration and contained four identical subunits of molecular mass 66-67 kDa by SDS-polyacrylamide gel electrophoresis. Both forms of the NTPase were activated by dithiothreitol, and NTPase-I had a specific activity 4.5-fold higher than NTPase-II in hydrolysis of ATP. The primary difference between these isozymes lies in their ability to hydrolyze nucleoside triphosphate versus diphosphate substrates. While NTPase-II hydrolyzed ATP to ADP and ADP to AMP at almost the same rate, NTPase-I hydrolyzed ADP to AMP at a much slower rate (0.7% of the rate for ATP). The complete cDNAs for NTPase-I and NTPase-II were sequenced and found to encode the same size predicted open reading frame of which only 16 of 628 amino acids differed between the two isozymes. Both forms of the NTPase contained an NH2-terminal hydrophobic signal peptide, consistent with our previous findings that these enzymes are secreted into the host cell vacuole occupied by the parasite. The gene encoding NTPase-II was found in all strains of Toxoplasma, while the NTPase-I was confined only to virulent strains. Expression of this highly active ATPase (NTPase-I) may contribute to intracellular survival and virulence of T. gondii.

本文言語English
ページ(範囲)11391-11397
ページ数7
ジャーナルJournal of Biological Chemistry
270
19
DOI
出版ステータスPublished - 1995
外部発表はい

ASJC Scopus subject areas

  • 生化学
  • 分子生物学
  • 細胞生物学

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