Bremaud L, Fremaux C, Laalami S, Cenatiempo Y
Institut de Biologie Moléculaire et d'Ingénierie Génétique-CNRS URA 1172, Université de Poitiers, France.
Nucleic Acids Res. 1995 May 25;23(10):1737-43. doi: 10.1093/nar/23.10.1737.
The tufB gene, encoding elongation factor Tu (EF-Tu), from the myxobacterium Stigmatella aurantiaca was cloned and sequenced. It is preceded by four tRNA genes, the first ever described in myxobacteria. The tRNA synthesized from these genes and the general organization of the locus seem identical to that of Escherichia coli, but differences of potential importance were found in the tRNA sequences and in the intergenic regions. The primary structure of EF-Tu was deduced from the tufB DNA sequence. The factor is composed of 396 amino acids, with a predicted molecular mass of 43.4 kDa, which was confirmed by expression of tufB in maxicells. Sequence comparisons between S.aurantiaca EF-Tu and other bacterial homologues from E.coli, Salmonella typhimurium and Thermus thermophilus displayed extensive homologies (75.9%). Among the variable positions, two Cys residues probably involved in the temperature sensitivity of E.coli and S.typhimurium EF-Tu are replaced in T.thermophilus and S.aurantiaca EF-Tu. Since two or even three tuf genes have been described in other bacterial species, the presence of multiple tuf genes was sought for. Southern and Northern analysis are consistent with two tuf genes in the genome of S.aurantiaca. Primer extension experiments indicate that the four tRNA genes and tufB are organized in a single operon.
对粘细菌橙黄粘球菌中编码延伸因子Tu（EF-Tu）的tufB基因进行了克隆和测序。该基因之前有四个tRNA基因，这是在粘细菌中首次发现的。从这些基因合成的tRNA以及该基因座的总体结构似乎与大肠杆菌的相同，但在tRNA序列和基因间区域发现了可能具有重要意义的差异。根据tufB DNA序列推导了EF-Tu的一级结构。该因子由396个氨基酸组成，预测分子量为43.4 kDa，通过在大细胞中表达tufB得到了证实。橙黄粘球菌EF-Tu与大肠杆菌、鼠伤寒沙门氏菌和嗜热栖热菌等其他细菌同源物之间的序列比较显示出广泛的同源性（75.9%）。在可变位点中，可能与大肠杆菌和鼠伤寒沙门氏菌EF-Tu的温度敏感性有关的两个半胱氨酸残基在嗜热栖热菌和橙黄粘球菌EF-Tu中被取代。由于在其他细菌物种中已经描述了两个甚至三个tuf基因，因此研究了橙黄粘球菌基因组中是否存在多个tuf基因。Southern和Northern分析表明橙黄粘球菌基因组中有两个tuf基因。引物延伸实验表明，四个tRNA基因和tufB组成一个单一的操纵子。
