Zinc-coordinating DNA-binding domains C2CH THAP-type zinc finger factors CLASSLINK:http\://www.edgar-wingender.de/class 2.9.html Class Class description: THAP-type zinc fingers follow the signature C- x(2-4)-C-x(35-50)-C-x2-H. Compared with 'canonical' C2H2 zinc fingers, those of THAP type exhibit an unusually long spacing between the first pair of cysteines and the following cysteine-histidine pair, which together coordinate one zinc ion. This long spacer adopts a beta-alpha-beta structure, with the second beta-strand right in front of the third cysteine. An additional short 3,10-helix comprises the zinc-coordinating histidine residue. The two beta-strands form a beta-sheet that inserts into the major groove, whereas the loop following the zinc finger exerts minor groove contacts. (PMID 18073205, PMID 20010837)