The carboxyl-terminal region of TFIIH is essential for transcription activity. This regions binds three zinc atoms through two independent domain. The first contains a C4 zinc finger motif, whereas the second is characterised by a CX(2)CX(2-4)FCADCD motif. The solution structure of the second C-terminal domain revealed homology with the regulatory domain of protein kinase C (Pfam:PF00130) [1].

1: Structural characterization of the cysteine-rich domain of TFIIH p44 subunit. Fribourg S, Kellenberger E, Rogniaux H, Poterszman A, Van Dorsselaer A, Thierry JC, Egly JM, Moras D, Kieffer B; J Biol Chem 2000;275:31963-31971. PMID:10882739