The blue-colored linker polypeptide L55 is a fusion protein of phycobiliproteins in the cyanobacterium synechocystis sp. strain BO 8402.
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.
Neuschaefer-Rube
O
O
Lehrstuhl für Physiologie und Biochemie der Pflanzen, Universität Konstanz, Germany. Olaf.Neuschaefer-Rube@uni-konstanz.de
Westermann
M
M
Blüggel
M
M
Meyer
H E
HE
Ernst
A
A
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
D001426:Bacterial Proteins; D045342:Light-Harvesting Protein Complexes; D010455:Peptides; D045524:Phycobilisomes; D010940:Plant Proteins; C411803:blue-colored linker polypeptide L55, Synechocystis; D010798:Phycocyanin