title: Molecular structure, localization and function of biliproteins in the chlorophyll a/d containing oxygenic photosynthetic prokaryote Acaryochloris marina.
abstract: We investigated the localization, structure and function of the biliproteins of the oxygenic photosynthetic prokaryote Acaryochloris marina, the sole organism known to date that contains chlorophyll d as the predominant photosynthetic pigment. The biliproteins were isolated by means of sucrose gradient centrifugation, ion exchange and gel filtration chromatography. Up to six biliprotein subunits in a molecular mass range of 15.5-18.4 kDa were found that cross-reacted with antibodies raised against phycocyanin or allophycocyanin from a red alga. N-Terminal sequences of the alpha- and beta-subunits of phycocyanin showed high homogeneity to those of cyanobacteria and red algae, but not to those of cryptomonads. As shown by electron microscopy, the native biliprotein aggregates are organized as rod-shaped structures and located on the cytoplasmic side of the thylakoid membranes predominantly in unstacked thylakoid regions. Biochemical and spectroscopic analysis revealed that they consist of four hexameric units, some of which are composed of phycocyanin alone, others of phycocyanin together with allophycocyanin. Spectroscopic analysis of isolated photosynthetic reaction center complexes demonstrated that the biliproteins are physically attached to the photosystem II complexes, transferring light energy to the photosystem II reaction center chlorophyll d with high efficiency.
authors.affiliation: Marine Biotechnology Institute, Kamaishi Laboratories, Kamaishi, Iwate, Japan. huqiang@imap4.asu.edu
authors.forename: Q
authors.initials: Q
authors.lastname: Hu
authors.forename: J
authors.initials: J
authors.lastname: Marquardt
authors.forename: I
authors.initials: I
authors.lastname: Iwasaki
authors.forename: H
authors.initials: H
authors.lastname: Miyashita
authors.forename: N
authors.initials: N
authors.lastname: Kurano
authors.forename: E
authors.initials: E
authors.lastname: Mörschel
authors.forename: S
authors.initials: S
authors.lastname: Miyachi
mesh_terms: D000595:Amino Acid Sequence; D002734:Chlorophyll / Q000737:chemistry*; D000458:Cyanobacteria; D045342:Light-Harvesting Protein Complexes; D008969:Molecular Sequence Data; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry; D045332:Photosystem II Protein Complex; D052980:Phycobilins; D010798:Phycocyanin / Q000737:chemistry*; D010799:Phycoerythrin / Q000737:chemistry*; D011387:Prokaryotic Cells / Q000737:chemistry*; D000461:Rhodophyta
chemical_list: D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D052980:Phycobilins; C002497:allophycocyanin; C038397:phycoerythrocyanin; D010798:Phycocyanin; D010799:Phycoerythrin; D002734:Chlorophyll; C107509:chlorophyll d