This domain represents a conserved region approximately 100 residues long within eukaryotic occludin proteins and the RNA polymerase II elongation factor ELL. Occludin is an integral membrane protein that localises to tight junctions [1], while ELL is an elongation factor that can increase the catalytic rate of RNA polymerase II transcription by suppressing transient pausing by polymerase at multiple sites along the DNA [2]. This shared domain is thought to mediate protein interactions [3].

1: Occludin: a novel integral membrane protein localizing at tight junctions. Furuse M, Hirase T, Itoh M, Nagafuchi A, Yonemura S, Tsukita S, Tsukita S; J Cell Biol 1993;123:1777-1788. PMID:8276896

2: An RNA polymerase II elongation factor encoded by the human ELL gene. Shilatifard A, Lane WS, Jackson KW, Conaway RC, Conaway JW; Science 1996;271:1873-1876. PMID:8596958

3: Structure of the conserved cytoplasmic C-terminal domain of occludin: identification of the ZO-1 binding surface. Li Y, Fanning AS, Anderson JM, Lavie A; J Mol Biol. 2005;352:151-164. PMID:16081103