Rpb5 has a bipartite structure which includes a eukaryote-specific N-terminal domain and a C-terminal domain resembling the archaeal RNAP subunit H [1,2]. The N-terminal domain is involved in DNA binding and is part of the jaw module in the RNA pol II structure [3]. This module is important for positioning the downstream DNA.

1: Crystal structure of RPB5, a universal eukaryotic RNA polymerase subunit and transcription factor interaction target. Todone F, Weinzierl RO, Brick P, Onesti S; Proc Natl Acad Sci U S A 2000;97:6306-6310. PMID:10841537

2: Solution structure of the RNA polymerase subunit RPB5 from Methanobacterium thermoautotrophicum. Yee A, Booth V, Dharamsi A, Engel A, Edwards AM, Arrowsmith CH; Proc Natl Acad Sci U S A 2000;97:6311-6315. PMID:10841538

3: Architecture of RNA polymerase II and implications for the transcription mechanism. Cramer P, Bushnell DA, Fu J, Gnatt AL, Maier-Davis B, Thompson NE, Burgess RR, Edwards AM, David PR, Kornberg RD; Science 2000;288:640-649. PMID:10784442

4: Sequence, structure and functional diversity of PD-(D/E)XK phosphodiesterase superfamily. Steczkiewicz K, Muszewska A, Knizewski L, Rychlewski L, Ginalski K; Nucleic Acids Res. 2012;40:7016-7045. PMID:22638584