J. Biochem, 1982, Vol. 91, No. 1 257-263
© 1982 Japanese Biochemical Society
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Studies on Purothionin by Chemical Modifications1
*Department of Biology, Faculty of Science, Osaka University Toyonaka, Osaka 560
**Suntory Institute for Biomedical Research Shimamoto-cho, Mishima, Osaka 618
Purothionin from wheat flour was chemically modified by acetic or succinic anhydride under specific conditions. The complete modification of all amino groups of purothionin caused a large change in the net charge of the molecule, leading to the loss of the toxicity to mice and yeast. The sole tyrosyl residue in purothionin was nitrated by tetranitromethane at neutral pH or iodinated by the lactoperoxidase method. The nitro- and diiodo-derivatives of purothionin showed considerably reduced toxicity. Based on these modification studies we conclude that the positive charges of lysyl residues have an important role in the interaction with the negatively charged cell surface, and that the emergence of the toxicity of purothionin depends on a certain state of the tyrosyl residue.
1 This work was aided in part by Grants-in-Aid for Scientific Research (No. 468060) and for Special Project Research (No. 512026), respectively, from the Ministry of Education, Science and Culture of Japan.
2 Present address: UNITIKA Ltd., Research and Development Center, 23 Uji-Kozakura, Uji, Kyoto 611.
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