異藻藍蛋白之生合成途徑探討

Study on the Biosynthesis Pathway of Allophycocyanin

胡宜忱(I-Chen Hu)

指導教授 ： 呂平江

國立清華大學/生命科學院/生物資訊與結構生物研究所/博士(2007年)

摘要

無資料

關鍵字

藻膽色素蛋白 ； 異藻藍蛋白 ； 發光團 ； 發光團裂解酶

並列摘要

Phycobiliproteins are valuable as fluorescent probes, because they are covalently attached with chromophores, giving them distinct absorption and emission spectra in the visible range. Allophycocyanin (APC), C-phycocyanin (CPC), and phycoerythrocyanin (PEC) are the three most common phycobiliproteins in cyanobacteria, and each contains the chromophore, phycocyanobilin (PCB). Chromophore lyases are needed to catalyze the attachment of chromophore to CPC and PEC. However, no APC-specific chromophore lyase has been reported.
PCB bonded APC α subunit (chromo-ApcA) was obtained via a spontaneous PCB attachment reaction. The extent of PCB attachment to apo-ApcA was comparable to that of the lyase-catalyzed reactions for other phycobiliproteins. The absorption and fluorescence characteristics of chromo-ApcA were similar to that of the native APC α subunit. These results indicate that ApcA has autocatalytic lyase activity.
Cys81 is the PCB bonded residue in ApcA, and its mutant failed to produce chromophorylated ApcA. In addition to Cys81, alanine substitution of Arg83, Asp84, Tyr87, and Tyr88 decreased the yield of chromoprotein and changed their spectral characteristics. Compared with CpcA, we inferred that Arg83, Asp84, Tyr87 and Tyr88 might be important for positioning the PCB in the correct orientation during bilin attachment.
Chromo-ApcB was obtained by either in vitro PCB assembly or direct production in E. coli. This spontaneous chromophorylation was region-specific to Cys81, and a covalent bond was formed. We proposed that recombinant ApcB, similar to ApcA, has the autocatalytic bilin:biliprotein activity.

並列關鍵字

Phycobiliproteins ； Allophycocyanin ； Chromophore ； Chromophore lyase

參考文獻

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