title: The blue-colored linker polypeptide L55 is a fusion protein of phycobiliproteins in the cyanobacterium synechocystis sp. strain BO 8402.
abstract: The cyanobacterium Synechocystis sp. strain BO 8402, isolated from Lake Constance, lacks phycobilisomes but instead forms inclusion bodies containing remnants of phycobiliproteins. The inclusion bodies are surrounded by a proteinaceous capsule and contain alpha-phycocyanin and beta-phycocyanin, the rod linker polypeptide L35RPC and a novel blue-colored protein L55 with an apparent molecular mass of 55 kDa. An antibody raised against beta-phycocyanin showed a strong cross-reaction with L55. Mass spectrometry analysis of proteolytic peptides from L55 revealed mass identity to proteolytic peptides derived from L35RPC and beta-phycocyanin. However, analysis of the genome of strain BO 8402 revealed only one cpcBACE operon, encoding the apoproteins of beta-phycocyanin and alpha-phycocyanin, L35RPC and a subunit of the phycocyanin alpha subunit phycocyanobilin lyase, respectively. The gene structure, sequence and transcription of these genes were identical to that of a revertant strain, Synechocystis sp. strain BO 9201, which formed phycobilisomes and did not express L55. Based on these observations, we concluded that L55 did not derive from a particular gene or from a special form of mRNA-processing. We propose that L55 is formed by post-translational fusion of L35RPC and beta-phycocyanin. Cross-linking may stabilize the formation of the large paracrystalline phycocyanin aggregates unique to Synechocystis sp. strain BO 8402.
authors.affiliation: Lehrstuhl für Physiologie und Biochemie der Pflanzen, Universität Konstanz, Germany. Olaf.Neuschaefer-Rube@uni-konstanz.de
authors.forename: O
authors.initials: O
authors.lastname: Neuschaefer-Rube
authors.forename: M
authors.initials: M
authors.lastname: Westermann
authors.forename: M
authors.initials: M
authors.lastname: Blüggel
authors.forename: H E
authors.initials: HE
authors.lastname: Meyer
authors.forename: A
authors.initials: A
authors.lastname: Ernst
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D015139:Blotting, Southern; D000458:Cyanobacteria / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002479:Inclusion Bodies / Q000378:metabolism; D045342:Light-Harvesting Protein Complexes; D008969:Molecular Sequence Data; D009876:Operon; D010455:Peptides / Q000235:genetics* / Q000378:metabolism*; D045524:Phycobilisomes; D010798:Phycocyanin / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D045342:Light-Harvesting Protein Complexes; D010455:Peptides; D045524:Phycobilisomes; D010940:Plant Proteins; C411803:blue-colored linker polypeptide L55, Synechocystis; D010798:Phycocyanin