8.A.235. The Chaparone Protein, Xport-A (Xprot-A) Family
Xport-A functions as a chaperone by stabilizing the first five transmembrane domains of rhodopsin-1 (Rh1) (Gaspar et al. 2023). Rhodopsin-1 is the main photosensitive protein of Drosophila. It is a seven-transmembrane domain protein, which is inserted co-translationally in the endoplasmic reticulum (ER) membrane. Biogenesis of Rh1 occurs in the ER, where various chaperones interact with Rh1 to aid in its folding and subsequent transport from the ER to the rhabdomere, the light-sensing organelle of the photoreceptors. Xport-A has been proposed as a chaperone/transport factor for Rh1. Gaspar et al. 2023 proposed a model where Xport-A functions as a chaperone during the biogenesis of Rh1 in the ER by stabilizing the first five TMSs of Rh1.
References:
Exit protein of rhodopsin and TRP B, isoform A, Xport-A, of 116 aas and 0 TMSs (Gaspar et al. 2023).
Xp[ort-A of Drosophila melanogaster (fruit fly)
Uncharacterized protein of 286 aas and 1 N-terminal TMS. The N-terminal domain (residues 1 - 41) is homologous to the same region of the protein listerd under TC# 8.A.235.1.1.
UP of Bombus bifarius
Uncharacterized protein of 137 aas and 1 N-terminal TMS.
UP of Bactrocera latifrons