Isolation and partial characterization of three protein-synthesis inhibitory proteins from the seeds of Luffa cylindrica.

DOI DOI PubMed 1 Citations Open Access
  • WATANABE Keiichi
    Laboratory of Biochemistry, Faculty of Agriculture, Kyushu University Present address: Department of Applied Biological Sciences, Saga University
  • MINAMI Yuji
    Laboratory of Biochemistry, Faculty of Agriculture, Kyushu University
  • FUNATSU Gunki
    Laboratory of Biochemistry, Faculty of Agriculture, Kyushu University

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Three new proteins which inhibit protein synthesis in rabbit reticulocyte lysates were isolated from an extract of sponge gourd (Luffa cylindrica) seeds by chromatography on a AF-Blue Toyopearl column followed by FPLC with a Mono S column. These three protein-synthesis inhibitory proteins (PSIs) have molecular masses of 19kDa, 15kDa, and 9kDa, and were designated 19K-PSI, 15K-PSI, and 9K-PSI, respectively. Although the 19K-PSI had no effect on protein synthesis in HeLa cells, its inhibitory activity on the cell-free protein synthesis was 340- and 83-fold stronger than those of ricin A-chain and luffin-a, respectively, probably due to hydrolyzing mRNA. The inhibitory activities of 15Kand 9K-PSIs on the cell-free protein synthesis were weaker than those of ricin A-chain and luffin-a. The 19K-PSI was a glycoprotein having an ordinary amino acid composition, three intramolecular disulfide bonds and a blocked N-terminal residue, while the 15K-PSI was extraordinarily rich in glycine and the 9K-PSI in arginine and glutamic acid (and/or glutamine). The amino acid composition of 19K-PSI was: Ser27Glx3Gly164Tyr7Lys9His6, and that of 9K-PSI was: Asx3Glx25Pro2Gly5Lys2His2Arg25Trp3.

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