Fling M E, Richards C
Nucleic Acids Res. 1983 Aug 11;11(15):5147-58. doi: 10.1093/nar/11.15.5147.
The complete nucleotide sequence of the type I dihydrofolate reductase gene from Tn7 was determined. The structural gene coded for a polypeptide of 157 amino acid residues. The polypeptide deduced from the DNA sequence had a molecular weight of 17,577 which was in good agreement with that estimated by mobility in SDS-polyacrylamide gels. Sequences were identified proximal to the coding region which were similar to those found in the consensus E. coli promoter region and for the initiation of protein synthesis. Features consistent with the termination of RNA transcription were present distal to the structural gene. No homology was apparent when the DNA sequence of the type I gene was compared to the sequence of the type II plasmid DHFR genes, but sequence homology was evident when the type I and E. coli chromosomal enzymes were compared. Homology was greatest in the regions coding for amino acids which in the E. coli chromosomal enzyme are associated with substrate, cofactor and inhibitor binding.
确定了来自Tn7的I型二氢叶酸还原酶基因的完整核苷酸序列。该结构基因编码一个由157个氨基酸残基组成的多肽。从DNA序列推导的多肽分子量为17577，这与通过SDS-聚丙烯酰胺凝胶电泳迁移率估计的分子量非常一致。在编码区近端鉴定出与大肠杆菌启动子共有区域中发现的序列以及蛋白质合成起始序列相似的序列。在结构基因远端存在与RNA转录终止一致的特征。当将I型基因的DNA序列与II型质粒二氢叶酸还原酶基因的序列进行比较时，没有明显的同源性，但当比较I型和大肠杆菌染色体酶时，序列同源性很明显。在编码与大肠杆菌染色体酶中与底物、辅因子和抑制剂结合相关的氨基酸的区域中同源性最大。
