Structure and apoprotein linkages of phycourobilin

Killilea, S.Derek; O'Carra, Pádraig

doi:10.1042/bj2260723

Cited by 13 publications

(12 citation statements)

References 28 publications

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“…1A, the PebA-like protein initially converted BV to produce 15,16-DHBV that was subsequently converted to a new product. The absorption spectrum of the new product was identical to that of phycourobilin (PUB) with maximum absorbance at 492 nm (18,19). In agreement with this interpretation, the molecular mass of the new product determined from mass spectroscopy was 4 Da larger than BV (Fig.…”

supporting

confidence: 72%

Distinct phytochrome actions in nonvascular plants revealed by targeted inactivation of phytobilin biosynthesis

Chen

2012

Proc. Natl. Acad. Sci. U.S.A.

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The red/far-red light photoreceptor phytochrome mediates photomorphological responses in plants. For light sensing and signaling, phytochromes need to associate with open-chain tetrapyrrole molecules as the chromophore. Biosynthesis of tetrapyrrole chromophores requires members of ferredoxin-dependent bilin reductases (FDBRs). It was shown that LONG HYPOCOTYL 2 (HY2) is the only FDBR in flowering plants producing the phytochromobilin (PΦB) for phytochromes. However, in the moss Physcomitrella patens, we found a second FDBR that catalyzes the formation of phycourobilin (PUB), a tetrapyrrole pigment usually found as the protein-bound form in cyanobacteria and red algae. Thus, we named the enzyme PUB synthase (PUBS). Severe photomorphogenic phenotypes, including the defect of phytochrome-mediated phototropism, were observed in Physcomitrella patens when both HY2 and PUBS were disrupted by gene targeting. This indicates HY2 and PUBS function redundantly in phytochrome-mediated responses of nonvascular plants. Our studies also show that functional PUBS orthologs are found in selected lycopod and chlorophyte genomes. Using mRNA sequencing for transcriptome profiling, we demonstrate that expression of the majority of red-light-responsive genes are misregulated in the pubs hy2 double mutant. These studies showed that moss phytochromes rapidly repress expression of genes involved in cell wall organization, transcription, hormone responses, and protein phosphorylation but activate genes involved in photosynthesis and stress signaling during deetiolation. We propose that, in nonvascular plants, HY2 and PUBS produce structurally different but functionally similar chromophore precursors for phytochromes. Holophytochromes regulate biological processes through light signaling to efficiently reprogram gene expression for vegetative growth in the light.

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confidence: 72%

Distinct phytochrome actions in nonvascular plants revealed by targeted inactivation of phytobilin biosynthesis

Chen

2012

Proc. Natl. Acad. Sci. U.S.A.

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“…The spectrum of this photoproduct was similar to those of the α-phycoerythrocyanin (α-PEC) photoproduct 56,57 and of phycourobilin. 52,58 The extinction coefficients of these teal-absorbing photoproducts could also be much higher than those for other states (Table S2), again reminiscent of the higher extinction coefficient of phycourobilin. 52 Denaturation analysis did not show the presence of phycourobilin in these proteins (Figure 4), although the possibility of a labile "urobilinoid" adduct cannot be dismissed.…”

Section: ■ Resultsmentioning

confidence: 96%

Phycoviolobilin Formation and Spectral Tuning in the DXCF Cyanobacteriochrome Subfamily

et al. 2012

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Phytochromes are red/far-red photosensory proteins that regulate adaptive responses to light via photoswitching of cysteine-linked linear tetrapyrrole (bilin) chromophores. The related cyanobacteriochromes (CBCRs) extend the photosensory range of the phytochrome superfamily to shorter wavelengths of visible light. CBCRs and phytochromes share a conserved Cys residue required for bilin attachment. In one CBCR subfamily, often associated with a blue/green photocycle, a second Cys lies within a conserved Asp-Xaa-Cys-Phe (DXCF) motif and is essential for the blue/green photocycle. Such DXCF CBCRs use isomerization of the phycocyanobilin (PCB) chromophore into the related phycoviolobilin (PVB) to shorten the conjugated system for sensing green light. We here use recombinant expression of individual CBCR domains in Escherichia coli to survey the DXCF subfamily from the cyanobacterium Nostoc punctiforme. We describe ten new photoreceptors with well-resolved photocycles and three additional photoproteins with overlapping dark-adapted and photoproduct states. We show that the ability of this subfamily to form PVB or retain PCB provides a powerful mechanism for tuning the photoproduct absorbance, with blue-absorbing dark states leading to a broad range of photoproducts absorbing teal, green, yellow, or orange light. Moreover, we use a novel green/teal CBCR that lacks the blue-absorbing dark state to demonstrate that PVB formation requires the DXCF Cys residue. Our results demonstrate that this subfamily exhibits much more spectral diversity than had been previously appreciated.

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“…PEB and PUB are isomeric compounds and each has two carboxylic groups. Killilea et al [27] postulated that there was a linkage between the ring C of phycourobilin and apoprotein which involves the hydroxy side chain group of serine in an ester linkage with the carboxylic group of the propionic side chain of PUB. Chromophores may influence the mobility of subunits (especially β-subunits) during electrophoresis under different conditions.…”

Section: Possible Mechanismsmentioning

confidence: 99%

Influence of Ionic Strength, pH, and SDS Concentration on Subunit Analysis of Phycoerythrins by SDS-PAGE

Zhao

Sun

et al. 2010

Appl Biochem Biotechnol

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Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) is often used for subunit analysis of proteins, but it is not efficient to make the alpha- and beta-subunits of phycoerythrins separated by normal SDS-PAGE. In this research, subunit components and subunit molecular weights of four purified phycoerythrins were analyzed by SDS-PAGE. Four factors including Tris concentration, pH, ammonium persulfate (APS), and SDS concentration were studied for their effects on SDS-PAGE of phycoerythrins. It showed that these factors can influence the separation of alpha- and beta-subunits, electrophoresis effect of gamma-subunits, apparent molecular weights of subunits, and mobility of marker proteins. The alpha- and beta-subunits separated better in the case of lower SDS concentration, lower Tris concentration, higher pH, and/or lower APS addition in separating gels. The molecular weights of alpha- and beta-subunits increased when Tris concentration increased in a certain range. It can be concluded that factors critical to subunit analysis by SDS-PAGE are SDS concentration and ionic strength, both of which are related to critical micelle concentration of SDS and ratio of SDS monomer to micelle in SDS-PAGE system. The ratio is postulated to influence SDS-PAGE by influencing the amount of SDS bound to polypeptides and shapes of polypeptide-SDS complexes.

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Structure and apoprotein linkages of phycourobilin

Cited by 13 publications

References 28 publications

Distinct phytochrome actions in nonvascular plants revealed by targeted inactivation of phytobilin biosynthesis

Distinct phytochrome actions in nonvascular plants revealed by targeted inactivation of phytobilin biosynthesis

Phycoviolobilin Formation and Spectral Tuning in the DXCF Cyanobacteriochrome Subfamily

Influence of Ionic Strength, pH, and SDS Concentration on Subunit Analysis of Phycoerythrins by SDS-PAGE

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