title: Genetic analysis of a 9 kDa phycocyanin-associated linker polypeptide.
abstract: The gene encoding LR9, a 9 kDa phycocyanin-associated linker polypeptide, was cloned from the cyanobacterium Synechococcus sp. PCC 7002 (Agmenellum quadruplicatum PR-6). This gene, termed cpcD, was located immediately 3' to cpcC, a gene which encodes another phycocyanin-associated linker, LR33. Mutation of cpcD by insertion led to the loss of LR9 as the only detectable change in phycobilisome composition. Cells and isolated phycobilisomes from the cpcD- strain did not detectably differ from the wild-type in absorption or steady-state fluorescence emission. Purified phycobilisomes from the wild-type and cpcD- strains were compared by electron microscopy. The number of phycocyanin discs in the rod substructures of the mutant was more variable than in the wild-type. Hence, one function of LR9 may be to minimize the heterogeneity of rod length, possibly by binding to the core-distal face of phycocyanin-LR33 complexes to prevent the tandem joining of such units. A mutant in which cpcD and cpcC-cpcD intergenic sequences are deleted shows a partial loss of LR33. Inverted repeats in this intergenic region may be required for optimal stability of the cpcC transcript.
authors.affiliation: Department of Molecular and Cell Biology, Pennsylvania State University Park 16802.
authors.forename: R
authors.initials: R
authors.lastname: de Lorimier
authors.forename: D A
authors.initials: DA
authors.lastname: Bryant
authors.forename: S E
authors.initials: SE
authors.lastname: Stevens
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D000458:Cyanobacteria / Q000235:genetics*; D005796:Genes; D045342:Light-Harvesting Protein Complexes; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D009154:Mutation; D010455:Peptides / Q000235:genetics*; D045524:Phycobilisomes; D010798:Phycocyanin / Q000235:genetics*; D010860:Pigments, Biological / Q000235:genetics*; D010940:Plant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000648:ultrastructure; D015183:Restriction Mapping; D012689:Sequence Homology, Nucleic Acid
chemical_list: C065673:LR9 peptide; D045342:Light-Harvesting Protein Complexes; D010455:Peptides; D045524:Phycobilisomes; D010860:Pigments, Biological; D010940:Plant Proteins; D010798:Phycocyanin