β-Carotene-Protein and Other Carotenoid-Proteins of Brown Algae and of Cyanophytes

Abstract

Reaction centre complexes I and II (RCI, RCII) of green plants brown algae and cyanophytes show spectral and HPLC evidence of the presence of carotenoids (cf. Larkum and Barrett, 1983). Estimated from the absorption at 480–500 nm the amount of caro-tenoid is 2–3 times greater in RCII than in RCI of green plants: not all of this is 3-carotene (Brauman et al., 1982). In the RCs of brown algae only 3-carotene is found (molar ration P-700: Chla.: β-carotene of 1:38: 4). Attempts to remove the inner antenna β-carotene with detergents causes collapse of the spectral features of the red absorption of the RCs, and disappearance of the long wave fluorescence emission peaks but an increase in the overall fluorescence. The question is raised as to whether the β-carotene is bound in a single pigment protein complex or is directly associated with Chla. molecules in the same protein. In experiments in which RCI and RCII of the brown seaweed Acrocarpia paniculata were exposed to the steroid detergents cholate or deoxycholate (<0.1% w/v) no shifts of the A_max were seen.