InterPro domain: IPR045037

PhLPs contain a TRX-like domain without the redox active CXXC motif. They are conserved in eukaryotes from yeast to human. They interact with trimeric G-proteins and function as co-chaperones in the cytosolic protein folding machinery [ 1 ]. The gene name for the human protein is TxnDC9. The two characterised members are described as Phd-like proteins, Plp1 of Saccharomyces cerevisiae and PhLP3 of Dictyostelium discoideum. Gene disruption experiments show that both Plp1 and PhLP3 are non-essential proteins [ 2 , 3 ].

It was assumed that PhLPs are not redox active due to the lack of a discernable [CXXC] active site motif that is characteristic for many redox active Trx and Trx-like proteins. However, recombinant PbPhLP-3 has been shown to exhibit redox activity. It serves as a possible link between the thioredoxin system and the CCT (chaperonin containing TCP-1) complex [ 4 ].

1. Function of phosducin-like proteins in G protein signaling and chaperone-assisted protein folding. Cell Signal 19, 2417-27
2. Functional analysis of Plp1 and Plp2, two homologues of phosducin in yeast. J Biol Chem 275, 18462-9
3. Phosducin-like proteins in Dictyostelium discoideum: implications for the phosducin family of proteins. EMBO J 22, 5047-57
4. Characterization of a protozoan Phosducin-like protein-3 (PhLP-3) reveals conserved redox activity. PLoS One 13, e0209699