Disease relevance of phycocyanobilin

• The cyanobacterium Synechococcus sp. PCC 7002 has eight distinct bilin attachment sites on seven polypeptides, all of which carry the same chromophore, phycocyanobilin [1].
• Fully segregated Synechocystis sp. PCC 6803 bvdR interposon mutants produce approximately 85% of the normal amount of phycobilisome cores containing allophycocyanin and other phycocyanobilin-bearing core polypeptides, but no detectable phycocyanin [2].
• Together with other bilins such as phycocyanobilin it serves as a light-harvesting pigment in the photosynthetic light-harvesting structures of cyanobacteria called phycobilisomes [3].
• Reconstitution of blue-green reversible photoconversion of a cyanobacterial photoreceptor, PixJ1, in phycocyanobilin-producing Escherichia coli [4].
• We show that free biliverdin or phycocyanobilin, highly enriched in the ZZE isomer, can easily be obtained from chromophores bound in a noncovalent manner to Agrobacterium phytochrome Agp1, and used for spectral assays [5].

High impact information on phycocyanobilin

• Phycocyanobilin:ferredoxin oxidoreductase (PcyA), one such FDBR, is a new class of radical enzymes that require neither cofactors nor metals and serially reduces the vinyl group of the D-ring and A-ring of BV using four electrons from ferredoxin to produce phycocyanobilin, one of the phytobilins [6].
• Phycocyanobilin and similar tetrapyrroles are covalently attached within seconds, an autocatalytic process followed by slow conformational changes culminating in red-absorbing phytochrome formation [7].
• Phycocyanobilin:ferredoxin oxidoreductase is a member of the ferredoxin-dependent bilin reductase family and catalyzes two vinyl reductions of biliverdin IXalpha to produce phycocyanobilin, the pigment precursor of both phytochrome and phycobiliprotein chromophores in cyanobacteria [8].
• CpeS acts as a phycocyanobilin: Cys-beta84-phycobiliprotein lyase that can attach, in vitro and in vivo, phycocyanobilin (PCB) to cysteine-beta84 of the apo-beta-subunits of C-phycocyanin (CpcB) and phycoerythrocyanin (PecB) [9].
• In cyanobacteria, the biosynthesis of the phycobiliprotein and phytochrome chromophore precursor phycocyanobilin is catalyzed by the ferredoxin-dependent enzyme phycocyanobilin:ferredoxin oxidoreductase (PcyA), which mediates an atypical four-electron reduction of biliverdin IXalpha [10].

Chemical compound and disease context of phycocyanobilin

• Ultrafast dynamics of phytochrome from the cyanobacterium synechocystis, reconstituted with phycocyanobilin and phycoerythrobilin [11].
• A phytochrome-encoding cDNA from the cyanobacterium Synechocystis has been heterologously expressed in Escherichia coli and reconstituted into functional chromoproteins by incubation with either phycocyanobilin (PCB) or phytochromobilin (PPhiB) [12].

Biological context of phycocyanobilin

• The ease of co-valent adduct formation strongly suggests that the ethylidene side chain is an important binding site of phycocyanobilin to the polypeptide chain [13].
• The amino acid sequences of the alpha and beta subunits of C. caldarium phycocyanin are also similar, and by proper alignment of the sequences it can be shown that the beta subunit contains a 12-residue insertion where the second phycocyanobilin chromophore is covalently attached [14].
• Novel activity of a phycobiliprotein lyase: both the attachment of phycocyanobilin and the isomerization to phycoviolobilin are catalyzed by the proteins PecE and PecF encoded by the phycoerythrocyanin operon [15].
• Genes for the apo-phycoerythrocyanin alpha subunit (pecA) and the heterodimeric lyase/isomerase (pecE and pecF), which catalyzes both the covalent attachment of phycocyanobilin and its concurrent isomerization to phycobiliviolin, were expressed from the trc promoter on a second plasmid [16].
• The nucleotide sequence extending 3' from RPCII genes in strain WH8020 revealed two open reading frames homologous to components of an alpha CPC phycocyanobilin lyase [17].

Anatomical context of phycocyanobilin

• Investigations with the rice phytochrome A phycocyanobilin adduct (PHYA*) and the tobacco phytochrome B phycocyanobilin adduct (PHYB*) show that the protein stability in yeast is independent of the form of the photoreceptor [18].
• Chromic acid degradation of phycobiliproteins from protoplast preparations incubated with delta-amino[4-14C] levulinic acid yielded radiolabeled imides which were derived from the phycocyanobilin chromophore [19].

Associations of phycocyanobilin with other chemical compounds

• The results indicate that the transformation of biliverdin to phycocyanobilin catalyzed by C. caldarium extracts is a ferredoxin-linked reduction process [20].
• Kinetic measurements establish that although the chromophore binding site on apophytochrome is best tailored to phytochromobilin, apophytochrome will accommodate the two analogs with modified D-rings, phycocyanobilin and phycoerythrobilin [21].
• Methanol adduct formation of phycocyanobilin can occur subsequent to cleavage and requires acid catalysis [13].
• An enzyme extract from the phycocyanin-containing unicellular rhodophyte, Cyanidium caldarium, reductively transforms biliverdin IX alpha to phycocyanobilin, the chromophore of phycocyanin, in the presence of NADPH [22].
• In parallel, the local increase in the medium pH associated with protonation then forwards a deprotonation at an acidic NH-group so that in effect both protonated and deprotonated phycocyanobilin would arise from the initial photoreaction and account for the observed red shift in the spectra of the B- and C-forms [23].

Gene context of phycocyanobilin

• Reduced phycocyanin and phycocyanobilin, the chromophore of phycocyanin are poor inhibitors of COX-2 without COX-2 selectivity [24].
• In the cyanobacterium Synechococcus sp. PCC 7002, the addition of phycocyanobilin to apo-alpha PC is catalyzed by the protein products of the cpcE and cpcF genes [25].
• The cpcE gene product is involved in the attachment of the phycocyanobilin chromophore to the alpha subunit of phycocyanin [26].
• Functional analysis of yeast-derived phytochrome A and B phycocyanobilin adducts [27].
• Spectroscopic analysis of photochromic phycocyanobilin and fluorescent phycoerythrobilin adducts of a 24-kDa fragment of Cph2 definitively established that the motif identified by pattern searches represents a bona fide bilin lyase domain [28].

Analytical, diagnostic and therapeutic context of phycocyanobilin

• After trypsin digestion and reverse phase high performance liquid chromatography, the CpcT reaction product produced one major phycocyanobilin-containing peptide [29].
• Assignments of the Pfr-Pr FTIR difference spectrum of cyanobacterial phytochrome Cph1 using 15N and 13C isotopically labeled phycocyanobilin chromophore [30].
• Structural factors important for binding are (i) the presence of a central metal with open ligation site, which even induces binding of phycocyanobilin, and (ii) the absence of the hydrophobic esterifying alcohol, phytol [31].

References