C-terminal zinc ribbon domain of RPC11 subunit of RNA polymerase III
The C-terminal zinc ribbon domain (C-ribbon) of subunit C11 (Zn-ribbon_RPC11) in RNA polymerase (Pol) III is required for intrinsic transcript cleavage. RPC11 is also involved in Pol III termination. Eukaryote genomes are transcribed by three nuclear RNA polymerases (Pol I, II and III) that share some subunits. RPC11 has strong homology to RPB9 of Pol II and RPA12 of Pol I. Zn-ribbon_RPC11 is homologous to Pol II elongation factor TFIIS domain III. C11 has two zinc-binding domains separated by a flexible linker.
Comment:The zinc ribbon is the most conserved part of RPB9, RPC11, RPA12 subunits of RNA polymerases and it is homologous to TFIIS domain III and the C-terminal zinc ribbon domain of archaeal Transcription Factor S. Three antiparallel b-sheets are stabilized by a tetrad of cysteines that chelate zinc