Green G A, Schué V, Monteil H
Laboratoire de Toxinologie Bactérienne, Université Louis-Pasteur, Strasbourg, France.
Gene. 1995 Aug 8;161(1):57-61. doi: 10.1016/0378-1119(95)00263-6.
Hybridization of an oligodeoxyribonucleotide (oligo) probe, designed from a repeated sequence ('oligo rep') at the C terminus of the Clostridium difficile (Cd) cytotoxin (Cyt), revealed that homologies exist between the Cd cyt gene and the genomes of several other clostridia, including Clostridium sordellii (Cs), suggesting a common ancestral cyt amongst the Clostridium genus. This Cd 'oligo rep' probe was used to clone the Cs (strain 6018) cyt. The sequenced (7095 bp) region encodes 2364 amino acids (aa) and corresponds to a protein of 270,614 Da. Cs Cyt has 76% identity with the Cd Cyt and 47% identity with the Cd enterotoxin (Ent). The latter third of the protein consists of repeated units, similar to those found for Cd Cyt. A highly conserved hydrophobic domain can be delineated. Few structural differences are evident between Cd and Cs Cyt to explain their different cellular and sub-cellular effects. A small open reading frame (ORF) encoding a protein of 16,484 Da is located 210 bp downstream from cyt. No homology was evident with any known sequence. The first 30 aa of this ORF may correspond to a signal peptide.
从艰难梭菌（Cd）细胞毒素（Cyt）C末端的重复序列（“oligo rep”）设计的寡脱氧核糖核苷酸（oligo）探针杂交显示，Cd细胞毒素基因与包括索氏梭菌（Cs）在内的其他几种梭菌的基因组之间存在同源性，这表明梭菌属中存在一个共同的祖先细胞毒素。这个Cd“oligo rep”探针被用于克隆Cs（6018菌株）细胞毒素。测序的（7095 bp）区域编码2364个氨基酸（aa），对应于一个270,614 Da的蛋白质。Cs细胞毒素与Cd细胞毒素有76%的同一性，与Cd肠毒素（Ent）有47%的同一性。该蛋白质的后三分之一由重复单元组成，类似于在Cd细胞毒素中发现的那些。可以勾勒出一个高度保守的疏水域。Cd和Cs细胞毒素之间几乎没有明显的结构差异来解释它们不同的细胞和亚细胞效应。一个编码16,484 Da蛋白质的小开放阅读框（ORF）位于细胞毒素下游210 bp处。与任何已知序列均无明显同源性。该ORF的前30个氨基酸可能对应于一个信号肽。
