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bilin' full
No full textbileRegatta Day] if a man chooses to become "bilin' full, ye know," at nine o'clock in the morning and dead to the world at ten, it's his own affair, . . .PRINTED ITEMW. J. KIRWIN NOV 12 1964Not usedNot usedNot use
Inflation and Inflation Uncertainty in Turkey : Evidence from the Past Two Decades
No full textBilin Neyapt
Bilin-Dependent Photoacclimation in <i>Chlamydomonas reinhardtii</i>
No full textIn land plants, linear tetrapyrrole (bilin)-based phytochrome photosensors optimize photosynthetic light capture by mediating massive reprogramming of gene expression. But, surprisingly, many green algal genomes lack phytochrome genes. Studies of the heme oxygenase mutant (hmox1) of the green alga Chlamydomonas reinhardtii suggest that bilin biosynthesis in plastids is essential for proper regulation of a nuclear gene network implicated in oxygen detoxification during dark-to-light transitions. hmox1 cannot grow photoautotrophically and photoacclimates poorly to increased illumination. We show that these phenotypes are due to reduced accumulation of photosystem I (PSI) reaction centers, the PSI electron acceptors 5'-monohydroxyphylloquinone and phylloquinone, and the loss of PSI and photosystem II antennae complexes during photoacclimation. The hmox1 mutant resembles chlorophyll biosynthesis mutants phenotypically, but can be rescued by exogenous biliverdin IXα, the bilin produced by HMOX1. This rescue is independent of photosynthesis and is strongly dependent on blue light. RNA-seq comparisons of hmox1, genetically complemented hmox1, and chemically rescued hmox1 reveal that tetrapyrrole biosynthesis and known photoreceptor and photosynthesis-related genes are not impacted in the hmox1 mutant at the transcript level. We propose that a bilin-based, blue-light-sensing system within plastids evolved together with a bilin-based retrograde signaling pathway to ensure that a robust photosynthetic apparatus is sustained in light-grown Chlamydomonas
Crystal structure and molecular mechanism of an E/F type bilin lyase-isomerase
No full textInternational audienceChromophore attachment of the light-harvesting apparatus represents one of the most important post-translational modifications in photosynthetic cyanobacteria. Extensive pigment diversity of cyanobacteria critically depends on bilin lyases that covalently attach chemically distinct chromophores to phycobiliproteins. However, how bilin lyases catalyze bilin ligation reactions and how some lyases acquire additional isomerase abilities remain elusive at the molecular level. Here, we report the crystal structure of a representative bilin lyase-isomerase MpeQ. This structure has revealed a “question-mark” protein architecture that unambiguously establishes the active site conserved among the E/F-type bilin lyases. Based on structural, mutational, and modeling data, we demonstrate that stereoselectivity of the active site plays a critical role in conferring the isomerase activity of MpeQ. We further advance a tyrosine-mediated reaction scheme unifying different types of bilin lyases. These results suggest that lyases and isomerase actions of bilin lyases arise from two coupled molecular events of distinct origi
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Bilin-dependent regulation of chlorophyll biosynthesis by GUN4
No full textBiosyntheses of chlorophyll and heme in oxygenic phototrophs share a common trunk pathway that diverges with insertion of magnesium or iron into the last common intermediate, protoporphyrin IX. Since both tetrapyrroles are pro-oxidants, it is essential that their metabolism is tightly regulated. Here, we establish that heme-derived linear tetrapyrroles (bilins) function to stimulate the enzymatic activity of magnesium chelatase (MgCh) via their interaction with GENOMES UNCOUPLED 4 (GUN4) in the model green alga Chlamydomonas reinhardtii A key tetrapyrrole-binding component of MgCh found in all oxygenic photosynthetic species, CrGUN4, also stabilizes the bilin-dependent accumulation of protoporphyrin IX-binding CrCHLH1 subunit of MgCh in light-grown C. reinhardtii cells by preventing its photooxidative inactivation. Exogenous application of biliverdin IXα reverses the loss of CrCHLH1 in the bilin-deficient heme oxygenase (hmox1) mutant, but not in the gun4 mutant. We propose that these dual regulatory roles of GUN4:bilin complexes are responsible for the retention of bilin biosynthesis in all photosynthetic eukaryotes, which sustains chlorophyll biosynthesis in an illuminated oxic environment
A Red/Green Cyanobacteriochrome Sustains Its Color Despite a Change in the Bilin Chromophore’s Protonation State
No full textThe second GAF domain of AnPixJ,
AnPixJg2, a bilin-binding protein
from the cyanobacterium <i>Anabaena</i> PCC 7120, undergoes
a photoinduced interconversion between a red-absorbing state, Pr,
and a green-absorbing state, Pg. Combining ultraviolet–vis
(UV–vis), infrared, resonance Raman (RR), and magic-angle spinning
(MAS) nuclear magnetic resonance (NMR) spectroscopy, we have studied
this cyanobacteriochrome (CBCR) assembled with phycocyanobilin (PCB)
either <i>in vivo</i> or <i>in vitro</i>. In both
assembly routes, the spectroscopic data of the Pr state reveal nearly
identical chromophore structures with a protonated (cationic) bilin.
However, unlike the native (<i>in vivo</i> assembly) Pg
photoproduct, in which the bilin retains protonation, the Pg generated
from the <i>in vitro</i>-assembled AnPixJg2 harbors a deprotonated
(neutral) bilin chromophore at pH 7.8. IR difference spectroscopy
further reveals the transfer of a proton from the bilin to a side-chain
carboxylate on an amino acid, probably Asp291. Besides the change
in protonation state, the bilin structure is very similar in the <i>in vitro</i>- and <i>in vivo</i>-assembled Pg photoproducts.
The chromophore of the <i>in vitro</i> Pg becomes protonated
when the pH is increased to 10, presumably because of a partial reversal
of protein misfolding. Most remarkably, the electronic transitions
remain unchanged and are very similar to those of the native Pg. Thus,
bilin protonation is not a key parameter for controlling the energies
of the electronic transitions in AnPixJg2. Possible alternative molecular
mechanisms for color tuning are discussed
Die Vertreibung der Deutschen aus Bilin ein Studien- und Quellenbuch zur Geschichte des Heimatkreises Bilin
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