1.A.11.4.12
The rhesus protein, Rhp1, of 479 aas and 11 TMSs.  Reef-building corals maintain an intracellular photosymbiotic association with dinoflagellate algae. As the algae are hosted inside the symbiosome, all metabolic exchanges must take place across the symbiosome membrane. Thies et al. 2022 established that Acropora yongei Rh (ayRhp1) facilitates transmembrane NH3 and CO2 diffusion, and that it is present in the symbiosome membrane. Furthermore, ayRhp1 abundance in the symbiosome membrane was highest around midday and lowest around midnight. Probably ayRhp1 mediates a symbiosomal NH₄⁺-trapping mechanism that promotes nitrogen delivery to algae during the day - necessary to sustain photosynthesis-and restrict nitrogen delivery at night-to keep the algae under nitrogen limitation (Thies et al. 2022).