Catalyzes the cyclization of both ends of lycopene to form beta-carotene, a retinal precursor. Is required for bacteriorhodopsin biogenesis, a light-driven proton pump with a covalently bound retinal cofactor. a carotenoid psi-end group = a carotenoid beta-end derivative all-trans-lycopene = gamma-carotene gamma-carotene = all-trans-beta-carotene Carotenoid biosynthesis; beta-carotene biosynthesis. Belongs to the lycopene beta-cyclase family. Truncated N-terminus.