title: The complete amino-acid sequence of C-phycoerythrin from the cyanobacterium Fremyella diplosiphon.
abstract: The amino-acid sequences of both subunits of C-phycoerythrin from the cyanobacterium Fremyella diplosiphon have been determined. The alpha-subunit contains 164 amino acid residues, two phycoerythrobilin (PEB) chromophores and has a molecular mass of 18,368 Da (protein: 17,192 Da + 2 PEB, one PEB accounting for 588 Da). The beta-subunit consists of 184 residues, three PEB chromophores and has a molecular mass of 20,931 Da (protein: 19,168 Da and 3 PEB: 1,764 Da). The five PEB chromophores (open chain tetrapyrroles) are covalently bound to six cysteine residues (one of them doubly bound to two cysteine residues). On the alpha-subunit, the first chromophore was found at position 84, homologous to the chromophore binding site of the other biliproteins APC, PC and PEC. The second chromophore, unique for the alpha-subunit of PE, is inserted together with a pentapeptide at position 143 a. On the beta-subunit, a doubly bound chromophore is attached to cysteine residues 50 and 61, similar to the rhodophytan phycoerythrins (B-PE and R-PE). The second and third chromophores were found at positions 84 and 155, homologous to the other biliproteins. A unique peptide insertion of 14 amino acid residues (without chromophore) was found at position 141 a-o in the beta-subunit and probably is located in the three-dimensional model near the additional chromophores of the C-PE alpha- and beta-subunits. Both additional chromophores of the C-PE alpha- and beta-subunit may be located at the periphery of the C-PE-trimer. The amino-acid sequence homology between C-PE alpha- and beta-subunit is 26% and to the alpha- and beta-subunits of C-PC from Mastigocladus laminosus 49% and 48%, respectively.
mesh_terms: D000595:Amino Acid Sequence; D002850:Chromatography, Gel; D000458:Cyanobacteria / Q000032:analysis*; D010450:Endopeptidases / Q000494:pharmacology; D019811:Hydroxylamine; D006898:Hydroxylamines / Q000494:pharmacology; D008666:Metalloendopeptidases; D010798:Phycocyanin / Q000032:analysis; D010799:Phycoerythrin / Q000032:analysis / Q000302:isolation & purification*; D010860:Pigments, Biological / Q000302:isolation & purification*; D014357:Trypsin / Q000494:pharmacology; D014961:X-Ray Diffraction
chemical_list: D006898:Hydroxylamines; D010860:Pigments, Biological; D010798:Phycocyanin; D010799:Phycoerythrin; D019811:Hydroxylamine; D010450:Endopeptidases; D014357:Trypsin; D008666:Metalloendopeptidases; C022653:auR protein, Staphylococcus aureus