传输factors（TFs）are key cellular components that control the first step of gene expression，thetranscriptionof DNA into RNA sequences.By ensuring the correct expression of specific genes，the transcriptional regulatory system plays a central part in controlling many biological processes，ranging from中央循环处理并进轨道测量和physiological balance，to cellular分配，分配and developmental time courses.TFs may be constitutively active or conditionally active.The most commonTFs classification of TFsis based on the structure of their DNA-binding domains.Grouping TFs by structural domain has been extremely useful in uncovering howthey recognize and bind specific DNA sequences，as well as providing insights into their evolutionary histories.Moreover，in some instances the DNA-binding domain provides clues to their function[1].A comprehensive classification recognizes four superfamilies with well-defined structural homology:基本域TFs（1），Zinc-coordinating domains TFs（2），helix-turn-helix（HTH）domains TFs（3），andbeta-scaffold domains with Minor Groove Contacts TFs（4）。预应力，预应力的TFs exists for which no superclass ass assignment can be done yet because of lack of structural information[2]。