Parasporin-1, a novel cytotoxic protein to human cells from non-insecticidal parasporal inclusions of Bacillus thuringiensis

J Biochem. 2005 Jan;137(1):17-25. doi: 10.1093/jb/mvi003.


Pro-parasporin-1 is a parasporal inclusion protein of the non-insecticidal Bacillus thuringiensis strain A1190. Cytotoxic fragments, named parasporin-1, were generated from pro-parasporin-1 by trypsin digestion. Parasporin-1 was purified by a combination of chromatography procedures based on the cytotoxic activity to HeLa cells. Two different fragments of 15-kDa and 56-kDa were detected in the purified parasporin-1 fraction. These fragments were tightly associated with each other and could not be separated by chromatography under conditions that preserve cytotoxic activity, indicating that the active form of parasporin-1 is a heterodimer of the 15- and 56-kDa fragments. Amino acid sequencing and MALDI-TOF mass spectrometric analysis revealed that parasporin-1 is generated from pro-parasporin-1 by trypsin digestion at Arg 93 and Arg 231. Of 12 human cell lines tested, parasporin-1 showed strong cytotoxicity to four cell lines derived from cancer tissues, but low to no cytotoxicity to the other cell lines. The time-courses of cytotoxicity indicated that the mode of action of parasporin-1 to sensitive cells differs from that shown for previously isolated cytotoxic proteins from Bacillus thuringiensis, Cyt proteins, and other bacterial pore-forming toxins. Thus, parasporin-1 is a novel cytotoxic protein to human cancer cells produced by B. thuringiensis, and may be useful as a tool to recognize and destroy specific cancer cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bacillus thuringiensis / chemistry*
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / isolation & purification
  • Bacterial Proteins / toxicity*
  • Bacterial Toxins / chemistry
  • Bacterial Toxins / isolation & purification
  • Bacterial Toxins / toxicity*
  • Cell Line
  • Chlorocebus aethiops
  • Endotoxins / chemistry
  • Endotoxins / isolation & purification
  • Endotoxins / toxicity*
  • Humans
  • Mice


  • Bacterial Proteins
  • Bacterial Toxins
  • Endotoxins
  • parasporin