Biochemical and immunochemical investigations on the light-harvesting system of the cryptophyte Rhodomonas sp.:: Evidence for a photosystem I specific antenna

Thylakoid membranes of the cryptophyte Rhodomonos sp. were solubilized with the mild detergent dodecyl-beta-mal-toside and subjected to sucrose density gradient centrifugation. The resulting gradients showed six pigment-bearing bands which were characterized further by means of absorption and fluorescence emission (77 K) spectroscopy, polyacrylamide gel electrophoresis and Western immunoblotting. Two of the bands showed characteristics of light-harvesting complexes, other bands could be attributed to photosystem II and photosystem I. Up to 10 different light-harvesting proteins could be identified, some of which are specific for photosystem I, others for photosystem II. The polypeptides of the light-harvesting complex of photosystem II show a higher chlorophyll c/a ratio than the antenna proteins of photosystem I. As in vascular plants, they represent the bulk of the membrane-intrinsic light-harvesting proteins.