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Fisheries Science

, Volume 75, Issue 1, pp 225–231 | Cite as

Structural characterization of plancitoxin I, a deoxyribonuclease II-like lethal factor from the crown-of-thorns starfish Acanthaster planci, by expression in Chinese hamster ovary cells

  • Ai Watanabe
  • Hiroshi Nagai
  • Yuji Nagashima
  • Kazuo Shiomi
Original Article Chemistry and Biochemistry

Abstract

Plancitoxin I, the major lethal factor from the spines of crown-of-thorns starfish Acanthaster planci, is a 37 kDa protein composed of two different subunits, and it has potent hepatotoxicity. It is homologous with mammalian deoxyribonuclease II (DNase II) and exhibits DNase activity responsible for the hepatotoxicity. To obtain information on the structure–activity relationship of plancitoxin I, various mutants were expressed in Chinese hamster ovary cells and examined for DNase activity. The results with deletion mutants revealed the requirement of the signal peptide for the expression of intact plancitoxin I and the inability of each subunit to hydrolyze DNA. Mutation at the N-glycosylation site (Asn-274) did not reduce DNase activity, supporting the absence of carbohydrate moieties in the molecule. The mutant H303A exhibited no DNase activity, suggesting the importance of His-303 for the enzymatic activity. No DNase activity was detected in C29A, C169A, C318A and C337A, indicating that four Cys residues are critical to the enzymatic activity. However, DNase activity was completely maintained in C263A and somewhat reduced in C277A and C357A. Based on the results with the Cys-specific mutants, plancitoxin I was assumed to contain three disulfide bridges (29–169, 277–357 and 318–337) and one free Cys-263.

Keywords

Acanthaster planci Chinese hamster ovary cell Crown-of-thorns starfish Deoxyribonuclease II Expression Plancitoxin I 

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Copyright information

© The Japanese Society of Fisheries Science 2008

Authors and Affiliations

  • Ai Watanabe
    • 1
  • Hiroshi Nagai
    • 2
  • Yuji Nagashima
    • 1
  • Kazuo Shiomi
    • 1
  1. 1.Department of Food Science and TechnologyTokyo University of Marine Science and TechnologyTokyoJapan
  2. 2.Department of Ocean SciencesTokyo University of Marine Science and TechnologyTokyoJapan

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