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Parasporins 1 and 2: Their structure and activity

Toshihiko Akiba1, Shiro Okumura2

  • 1Institute of Molecular and Cellular Biosciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan.

Journal of Invertebrate Pathology
|October 26, 2016
PubMed

Insights

Parasporins, toxins from Bacillus thuringiensis, show selective cancer cell killing. Structural analysis reveals two types: Cry toxins and beta-pore-forming toxins (β-PFTs), suggesting distinct mechanisms for cancer therapy.

Area of Science:

  • Biochemistry
  • Structural Biology
  • Molecular Toxicology

Background:

  • Parasporins are novel protein toxins derived from Bacillus thuringiensis.
  • They exhibit preferential cytotoxicity against human cancer cells.
  • Parasporins are classified into two types: three-domain Cry toxin type and β-pore-forming-toxin (β-PFT) type.

Purpose of the Study:

  • To elucidate the structural characteristics of two representative parasporins, PS1Aa1 (Cry type) and PS2Aa1 (β-PFT type).
  • To compare their structures with known toxins to understand their mechanisms of action and cellular specificity.
  • To explore the potential of parasporins as targeted cancer therapeutics.

Main Methods:

  • Determination of crystal structures for PS1Aa1 and PS2Aa1.
  • Comparative structural analysis with established insecticidal Cry toxins and aerolysin-type β-PFTs.
  • Analysis of structural domains related to oligomerization, pore formation, and receptor binding.

Main Results:

  • PS1Aa1 shares structural features with three-domain insecticidal Cry toxins but possesses an N-terminal segment suggesting an alternative apoptotic signaling role.
  • PS2Aa1 exhibits significant structural similarity to aerolysin-type β-PFTs, indicating a pore-forming mechanism.
  • Structural variations in the domain 1 receptor-binding region of PS2Aa1 likely contribute to its enhanced cancer cell specificity.

Conclusions:

  • Parasporins employ distinct structural mechanisms, either related to Cry toxins or β-PFTs, for their cytotoxic effects.
  • Structural insights support the potential of parasporins as targeted anticancer agents.
  • Further experimental validation is required to fully understand the mechanism of action and cellular specificity of both parasporin types.
Keywords:
Bacillus thuringiensisCry toxinParasporinThree-domain Cry toxinβ-pore-forming-toxin

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