Kupersztoch Y M, Tachias K, Moomaw C R, Dreyfus L A, Urban R, Slaughter C, Whipp S
Department of Microbiology, University of Texas Southwestern Medical Center, Dallas 75235.
J Bacteriol. 1990 May;172(5):2427-32. doi: 10.1128/jb.172.5.2427-2432.1990.
The methanol-insoluble, heat-stable enterotoxin of Escherichia coli synthesized by clinical strains or strains that harbor the cloned gene was shown to be an extracellular polypeptide. The toxin (STB) was first detected as an 8,100-Mr precursor (pre-STB) that was converted to a transiently cell-associated 5,200-Mr form. Proteolytic conversion of pre-STB to STB was shown to be inhibited by the proton motive force uncoupler carbonyl cyanide m-chlorophenylhydrazone and did not occur in a secA background. After STB was detected as a cell-associated molecule, an extracellular form with identical electrophoretic mobility became apparent. The results suggest that there is no proteolytic processing during the mobilization of STB from the periplasm to the culture supernatant. The determined amino acid sequence of STB coincides fully with the 48 carboxy-terminal amino acids inferred from the DNA sequence. The 23 amino-terminal residues inferred from the DNA sequence were absent in the mature toxin.
临床菌株或携带克隆基因的菌株合成的大肠杆菌甲醇不溶性、热稳定肠毒素被证明是一种细胞外多肽。该毒素（STB）最初被检测为一种8100道尔顿的前体（前STB），它会转化为一种与细胞短暂相关的5200道尔顿形式。前STB向STB的蛋白水解转化被质子动力解偶联剂羰基氰化物间氯苯腙抑制，且在secA背景中不会发生。在STB被检测为与细胞相关的分子后，具有相同电泳迁移率的细胞外形式变得明显。结果表明，在STB从周质转运到培养上清液的过程中没有蛋白水解加工。测定的STB氨基酸序列与从DNA序列推断的48个羧基末端氨基酸完全一致。成熟毒素中不存在从DNA序列推断的23个氨基末端残基。
