Abstract

P56, a protein with a molecular weight of 56 kDa, was isolated from the cell-free supernatant of Salmonella enterica serovar Choleraesuis CH12440 (Salmonella Choleraesuis CH12440) culture. Comparison of the N-terminal amino acid sequence of P56 with the sequences in GenBank indicated that it was flagellin, the product of fliC gene and the subunit of flagellar filament. The gene encoding P56 was cloned and expressed. Although the gene displayed a 99.2 % nucleotide sequence homology and a 98.6 % amino acid sequence homology with other S. Choleraesuis phase-1-c flagellin genes, there was an insert of 36 nucleotides absent in other phase-1-c flagellin genes. The expressed P56 protein was toxic to macrophage cell Raw264.7, and caused the programmed death of the cells in vitro.

中文摘要

P56是從豬霍亂沙門氏桿菌CH12440 (Salmonella Choleraesuis CH12440) 培養基上清液純化出來，分子量為56 kDa的蛋白質。將P56的N端胺基酸定序並與基因資料庫(GenBank)比對，發現它是一種鞭毛素(flagellin)。此蛋白為fliC基因的產物，是構成鞭毛絲狀體的次單元。我們將P56蛋白的基因選殖於大腸桿菌並表現其蛋白。雖然這個基因與其他S. Choleraesuis 第一型(phase-1-c)鞭毛素基因之核苷酸序列有99.2%的相似性，胺基酸序列有98.6%的相似性，但是在P56基因中有一連續36個核苷酸是其他S. Choleraesuis第一型鞭毛素基因所沒有。這個選殖基因表現出來的蛋白質對小鼠巨噬細胞Raw264.7具有毒性並會造成細胞的凋亡。

Keyword: Cytotoxin, Flagellin, Salmonella enterica serovar Choleraesuis, Programmed death, 細胞毒素, 鞭毛素, 豬霍亂沙門氏桿菌, 細胞凋亡