ABCA4

Flippase that catalyzes in an ATP-dependent manner the transport of retinal-phosphatidylethanolamine conjugates like 11-cis and all-trans isomers of N-retinylidene-phosphatidylethanolamine (N-Ret-PE) from the lumen to the cytoplasmic leaflet of photoreceptor outer segment disk membranes, where 11-cis-retinylidene-phosphatidylethanolamine is then isomerized to its all-trans isomer and reduced by RDH8 to produce all-trans-retinol. This transport activity ensures that all-trans-retinal generated from photoexcitation and 11-cis-retinal not needed for the regeneration of rhodopsin and cone opsins are effectively cleared from the photoreceptors, therefore preventing their accumulation and the formation of toxic bisretinoid. Displays ATPase activity in vitro in absence of retinal substrate. May display GTPase activity that is strongly influenced by the lipid environment and the presence of retinoid compounds. Binds the unprotonated form of N-retinylidene-phosphatidylethanolamine with high affinity in the absence of ATP, and ATP binding and hydrolysis induce a protein conformational change that causes N-retinylidene-phosphatidylethanolamine release (By similarity)..

Function from UniProtKB (P78363), read 2026-09-23. CC BY 4.0.