alpha-Kirilowin, a novel ribosome-inactivating protein from seeds of Trichosanthes kirilowii (family Cucurbitaceae): a comparison with beta-kirilowin and other related proteins.
A novel ribosome-inactivating protein (RIP) designated alpha-kirilowin was isolated from the seeds of Trichosanthes kirilowii. The molecular weight of alpha-kirilowin was estimated by SDS-polyacrylamide gel electrophoresis to be 28 800 Da, which is slightly larger than another previously characterized ribosome-inactivating protein, beta-kirilowin. The amino-acid composition of alpha-kirilowin grossly resembled beta-kirilowin and other ribosome-inactivating proteins isolated from T. kirilowii tissues, including trichokirin, trichosanthin and karasurin. Intense immunological cross-reactivity between the two kirilowins was detected by immunodiffusion. The N-terminal sequence of alpha-kirilowin was identical to that of beta-kirilowin, at least in the first ten residues. Peptide fingerprinting indicated both kirilowins were closely related. Biological activities as determined by inhibition of protein synthesis in a cell-free system, suppression of [3H]-thymidine incorporation into mouse melanoma cells and induction of abortion in mice were very similar for both kirilowins. We propose that the size difference between alpha- and beta-kirilowin is either due to a C-terminal extension in alpha-kirilowin or differences in glycosylation, or a combination of both.
Department of Biology, Hong Kong Baptist University.
R N
RN
Wong
T X
TX
Dong
T B
TB
Ng
W T
WT
Choi
H W
HW
Yeung
D000019:Abortifacient Agents / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D002474:Cell-Free System; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D005260:Female; D051379:Mice; D008813:Mice, Inbred ICR; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010940:Plant Proteins / Q000032:analysis / Q000494:pharmacology*; D010945:Plants, Edible / Q000737:chemistry*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011817:Rabbits; D012270:Ribosomes / Q000187:drug effects*; D012639:Seeds / Q000737:chemistry*
D000019:Abortifacient Agents; D010940:Plant Proteins; D011500:Protein Synthesis Inhibitors; C086066:beta-kirilowin protein, Trichosanthes kirilowii; C104445:kirilowin-alpha protein, Trichosanthes kirilowii