title: Biosynthesis of fluorescent allophycocyanin alpha-subunits by autocatalytic bilin attachment.
abstract: Allophycocyanin (APC) is one of the phycobiliproteins expressed in cyanobacteria. Phycobiliproteins contain a covalently bound chromophore, and thus, they are valuable as fluorescent probes. Biosynthesis of a functional phycobiliprotein is achieved by a bilin attachment process between the chromophore and apoprotein. Chromophore lyases are necessary to catalyze the chromophorylation of cyanobacterial phycobiliproteins, such as C-phycocyanin, and phycoerythrocyanin. To identify the lyase that catalyzes the chromophorylation of the APC alpha-subunit (ApcA), we searched the entire genomes of two cyanobacteria, Synechocystis sp. PCC6803 and Anabaena sp. PCC 7120; however, these genomes do not appear to encode an APC-specific chromophore lyase. In this study, chromophorylated ApcA (chromo-ApcA) was obtained via a spontaneous bilin attachment reaction. The absorption and fluorescence characteristics of chromo-ApcA were similar to those of the native APC alpha-subunit. The extent of chromophore attachment to apo-ApcA was comparable to that of the lyase-catalyzed reactions for other phycobiliproteins. These results indicate that ApcA has autocatalytic bilin:biliprotein lyase activity.
authors.affiliation: Department of Life Sciences and Institute of Bioinformatics and Structural Biology, National Tsing Hua University, Hsinchu, Taiwan.
authors.forename: I-Chen
authors.initials: IC
authors.lastname: Hu
authors.forename: Tian-Ren
authors.initials: TR
authors.lastname: Lee
authors.forename: Hui-Fen
authors.initials: HF
authors.lastname: Lin
authors.forename: Chuang-Chun
authors.initials: CC
authors.lastname: Chiueh
authors.forename: Ping-Chiang
authors.initials: PC
authors.lastname: Lyu
mesh_terms: D001483:Base Sequence; D001654:Bile Pigments / Q000378:metabolism*; D002384:Catalysis; D002942:Circular Dichroism; D017931:DNA Primers; D004591:Electrophoresis, Polyacrylamide Gel; D005453:Fluorescence; D010798:Phycocyanin / Q000096:biosynthesis*; D010957:Plasmids; D021241:Spectrometry, Mass, Electrospray Ionization; D046939:Synechocystis / Q000378:metabolism*
chemical_list: D001654:Bile Pigments; D017931:DNA Primers; C002497:allophycocyanin; D010798:Phycocyanin