This entry represents a family of hydrophobic presumed membrane proteins, mainly from Halobacteria. The representative member is CruF, a C50 carotenoid 2',3'-hydratase involved in the synthesis of the C50 carotenoid bacterioruberin in the halophilic archaeon Haloarcula japonica. CruF catalyses the reaction that introduces hydroxyl groups to C3'' and C3''' of bisanhydrobacterioruberin (BABR) to generate BR