This entry represents an integral membrane protein with 4 transmembrane helices. The second alpha helix contains a conserved glutamic acid residue and the third helix contains a conserved arginine residue. These two buried charged residues may interact. The type example for this family is the Phosphate-starvation-inducible E (PsiE) expression protein, which is under direct positive and negative control by PhoB and cAMP-CRP, respectively [1]. The function of PsiE remains to be determined. This entry is sometimes found in proteins that contain other domains such as Pfam:PF11563.

1: Dual transcriptional regulation of the Escherichia coli phosphate-starvation-inducible psiE gene of the phosphate regulon by PhoB and the cyclic AMP (cAMP)-cAMP receptor protein complex. Kim SK, Kimura S, Shinagawa H, Nakata A, Lee KS, Wanner BL, Makino K; J Bacteriol 2000;182:5596-5599. PMID:10986267