Burton Samuel P, Burton Zachary F
a Department of Biochemistry and Molecular Biology ; Michigan State University ; E. Lansing , MI USA.
Transcription. 2014;5(4):e967599. doi: 10.4161/21541264.2014.967599.
Structural comparisons of initiating RNA polymerase complexes and structure-based amino acid sequence alignments of general transcription initiation factors (eukaryotic TFIIB, archaeal TFB and bacterial σ factors) show that these proteins are homologs. TFIIB and TFB each have two-five-helix cyclin-like repeats (CLRs) that include a C-terminal helix-turn-helix (HTH) motif (CLR/HTH domains). Four homologous HTH motifs are present in bacterial σ factors that are relics of CLR/HTH domains. Sequence similarities clarify models for σ factor and TFB/TFIIB evolution and function and suggest models for promoter evolution. Commitment to alternate modes for transcription initiation appears to be a major driver of the divergence of bacteria and archaea.
起始RNA聚合酶复合物的结构比较以及通用转录起始因子（真核生物TFIIB、古细菌TFB和细菌σ因子）基于结构的氨基酸序列比对表明，这些蛋白质是同源物。TFIIB和TFB各自具有两到五个螺旋的细胞周期蛋白样重复序列（CLRs），其中包括一个C端螺旋-转角-螺旋（HTH）基序（CLR/HTH结构域）。细菌σ因子中存在四个同源的HTH基序，它们是CLR/HTH结构域的遗迹。序列相似性阐明了σ因子和TFB/TFIIB进化与功能的模型，并暗示了启动子进化的模型。对转录起始替代模式的选择似乎是细菌和古细菌分化的主要驱动力。
