-  Superclass
-  Zinc-coordinating DNA-binding domains
-  "TRANSFAC class description C0034: In polymerase III transcription factor TFIIIA, a repetitive pattern of cysteine and histidine residues was discovered and, together with the known zinc-dependence of TFIIIA, led to the model of 'zinc fingers' of the Cys2His2 type (PMID 3191912, PMID 6196359). Shortly after, sequences coding for the estrogen receptor were cloned and revealed a somewhat similar arrangement of cysteine residues only (Cys4), with no additional homologies (PMID 3755102, PMID 4040853). Nevertheless, a zinc finger model was proposed for these factors as well and was subsequently proven, with a minor alteration in the Cys pattern (PMID 3780678). In addition to these two large classes of zinc finger proteins, there are many factors revealing Cys4 zinc fingers of variable composition, such as the GATA-factors, some fungal regulators and adenovirus E1A. Finally, the yeast GAL4-like regulators are grouped together as Cys6 'zinc clusters'."