Yamamoto N, Kato R, Kuramitsu S
Department of Biology, Faculty of Science, Osaka University, Japan.
Gene. 1996 May 24;171(1):103-6. doi: 10.1016/0378-1119(96)00052-2.
One of the most important DNA repair systems is the nucleotide (nt) excision repair system. The uvr A gene, which plays an essential role in the prokaryotic excision repair system, was cloned from an extremely thermophilic eubacterium, Thermus thermophilus (Tt) HB8, and its nt sequence was determined. In the amino acid (aa) sequence of Tt UvrA, a characteristic duplicated structure, two nt-binding consensus sequences (Walker's A-type motif) and two zinc finger DNA-binding motifs were found. The aa sequence showed 73% homology with that of Escherichia coli (Ec). These features suggest that Tt has the same excision repair system as Ec. Upon comparison of the Tt and Ec UvrA, some characteristic aa substitutions were found. The numbers of Arg and Pro residues were increased (from 66 to 81 and from 47 to 55, respectively), and the numbers of Asn and Met residues were decreased (from 33 to 18 and from 18 to 11, respectively) in Tt. The Tt uvr A gene was expressed in Ec under control of the lac promoter. Purified UvrA was stable up to 80 degrees C (at neutral pH) and at pH 2-11 (at 25 degrees C).
最重要的DNA修复系统之一是核苷酸（nt）切除修复系统。在原核生物切除修复系统中起关键作用的uvr A基因，是从嗜热真细菌嗜热栖热菌（Tt）HB8中克隆出来的，并测定了其核苷酸序列。在Tt UvrA的氨基酸（aa）序列中，发现了一种特征性的重复结构、两个核苷酸结合共有序列（沃克A型基序）和两个锌指DNA结合基序。该氨基酸序列与大肠杆菌（Ec）的氨基酸序列具有73%的同源性。这些特征表明Tt具有与Ec相同的切除修复系统。在比较Tt和Ec UvrA时，发现了一些特征性的氨基酸替换。在Tt中，Arg和Pro残基的数量增加（分别从66个增加到81个和从47个增加到55个），而Asn和Met残基的数量减少（分别从33个减少到18个和从18个减少到11个）。Tt uvr A基因在lac启动子的控制下在Ec中表达。纯化后的UvrA在80摄氏度（中性pH）以及pH值为2至11（25摄氏度）的条件下都很稳定。
