X-ray crystallographic structure of the light-harvesting biliprotein C-phycocyanin from the thermophilic cyanobacterium Mastigocladus laminosus and its resemblance to globin structures

Schirmer, Tilman; Bode, Wolfram; Huber, Robert; Sidler, Walter; Zuber, Herbert

doi:10.1016/0022-2836(85)90379-1

Cited by 348 publications

(215 citation statements)

References 59 publications

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“…The reproducibility over many experiments, however, supports the existence of a series of intermediates with very similar extinction coefficients, which, in bilins, mainly depends on differences in molecular geometry (29,33,34). Free PCB, which has a relatively weak long-wavelength absorption (⑀ Ϸ 17 ϫ 10 3 M Ϫ1 cm Ϫ1 , Table 2), predominantly assumes a cyclic-helical conformation, whereas more extended conformations of PCB result in much more intense absorptions (29,(35)(36)(37)(38)(39). Thus, the relatively weak absorbencies of P650, P605, and P638 suggest that they all retain the cyclic conformation similar to that of free PCB and that the major conformational change occurs only during the last step.…”

Section: Assignment Of Intermediatesmentioning

confidence: 90%

“…Torsion of the bilin scaffold in the course of its interaction with protein components is a likely scenario. In all x-ray structures, the chromophores are non-planar, including the conjugated parts of the molecule (35,37,39,(45)(46)(47)(48)(49)(50). Although the exact location of the distortions is probably only reliable at a resolution Ͻ2 Å (46,50,51), pronounced deviations from planarity are obvious in all structures.…”

Section: Assignment Of Intermediatesmentioning

confidence: 99%

“…The other systems involve several other proteins, including heme-transporters ("chaperones"), and, only recently, has the lyase function been assigned to a pair of gene products, CcsA and CcsB (30). Again, no obvious homologies are so far apparent for either the phytochrome lyase domains or the phycobiliproteins lyases, even though the apoproteins of cytochromes are phylogenetically and structurally related to those of the biliproteins (35). Further, the heme-chromophore of the cytochromes is the biosynthetic precursor of the bilin chromophores of the biliproteins (5,67).…”

Section: Assignment Of Intermediatesmentioning

confidence: 99%

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Biliprotein Chromophore Attachment

Böhm

Endres

Scheer

et al. 2007

Journal of Biological Chemistry

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Biliproteins are post-translationally modified by chromophore addition. In phycoerythrocyanin, the heterodimeric lyase PecE/F covalently attaches phycocyanobilin (PCB) to cysteine-␣84 of the apoprotein PecA, with concomitant isomerization to phycoviolobilin. We found that: (a) PecA adds autocatalytically PCB, yielding a low absorbance, low fluorescence PCB⅐PecA adduct, termed P645 according to its absorption maximum; (b) In the presence of PecE, a high absorbance, high fluorescence PCB⅐PecA adduct is formed, termed P641; (c) PecE is capable of transforming P645 to P641; (d) When in stop-flow experiments, PecA and PecE were preincubated before chromophore addition, a red-shifted intermediate (P650, ‫؍‬ 32 ms) was observed followed by a second, which was blue-shifted (P605, ‫؍‬ 0.5 s), and finally a third (P638, ‫؍‬ 14 s) that yielded the adduct (P641, ‫؍‬ 20 min); (e) The reaction was slower, and P605 was missing, if PecA and PecE were not preincubated; (f) Gel filtration gave no evidence of a stable complex between PecA and PecE; however, complex formation is induced by adding PCB; and (g) A red-shifted intermediate was also formed, but more slowly, with phycoerythrobilin, and denaturation showed that this is not yet covalently bound. We conclude, therefore, that PecA and PecE form a weak complex that is stabilized by PCB, that the first reaction step involves a conformational change and/or protonation of PCB, and that PecE has a chaperone-like function on the chromoprotein.Phycobiliproteins are a family of light-harvesting proteins of cyanobacteria, rhodophytes, and cryptophytes (1-4). The apoproteins are post-translationally modified by regio-and stereoselective chromophore attachment to cysteines. Addition to the cysteine-␣84 of cyanobacterial phycocyanins and phycoerythrins is catalyzed by the heterodimeric E/F-type lyases (5). The first enzyme of this type studied, phycocyanobilin:cysteine-␣84-phycocyanin lyase, from the cyanobacterium, Synechococcus sp. PCC 7002, attaches phycocyanobilin (PCB) 3 to apo-␣-phycocyanin (CpcA) (6). It is encoded by two genes, cpcE and cpcF, located on the phycocyanin (CPC) operon downstream of the two apo-phycocyanin and two linker genes. A similar operon structure has been found in several other organisms, but the respective genes can also be located in other positions (5, 7). The functions of the two subunits are still unclear. Chromophore attachment to the phylogenetically related site on the ␤-subunit, cysteine-␤82, is catalyzed by a single-subunit protein, or mixtures of similar proteins (8, 9), whereas the chromophores are attached autocatalytically in phytochromes (10, 11), allophycocyanin, ApcA (12), and the core-membrane linker, ApcE (13). The situation is complicated by the capacity of apo-phycobiliproteins like CpcA/B to also add chromophores autocatalytically but only slowly and in an error-prone fashion (14 -17).The isomerizing phycoviolobilin:cysteine-␣84-phycoerythrocyanin lyase is a member of the E/F-type lyases, which, in addition to chromophore attachment, ha...

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Section: Assignment Of Intermediatesmentioning

confidence: 90%

Section: Assignment Of Intermediatesmentioning

confidence: 99%

Section: Assignment Of Intermediatesmentioning

confidence: 99%

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Biliprotein Chromophore Attachment

Böhm

Endres

Scheer

et al. 2007

Journal of Biological Chemistry

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“…The precise supramolecular architecture of PBS, as well as the specific locations of the PBPs within them, is mediated by socalled linker proteins (1)(2)(3). PBP structures exhibit high similarity in the overall structure, pigment binding environment, and subunit interactions (12)(13)(14)(15)(16).…”

Section: Phycobilisomes (Pbs)mentioning

confidence: 99%

Biogenesis of Phycobiliproteins

Shen

Schluchter

Bryant

2008

Journal of Biological Chemistry

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Phycobilin lyases covalently attach phycobilin chromophores to apo-phycobiliproteins (PBPs). Genome analyses of the unicellular, marine cyanobacterium Synechococcus sp. PCC 7002 identified three genes, denoted cpcS-I, cpcU, and cpcV, that were possible candidates to encode phycocyanobilin (PCB) lyases. Single and double mutant strains for cpcS-I and cpcU exhibited slower growth rates, reduced PBP levels, and impaired assembly of phycobilisomes, but a cpcV mutant had no discernable phenotype. A cpcS-I cpcU cpcT triple mutant was nearly devoid of PBP. SDS-PAGE and mass spectrometry demonstrated that the cpcS-I and cpcU mutants produced an altered form of the phycocyanin (PC) ␤ subunit, which had a mass ϳ588 Da smaller than the wild-type protein. Some free PCB (mass ‫؍‬ 588 Da) was tentatively detected in the phycobilisome fraction purified from the mutants. The modified PC from the cpcS-I, cpcU, and cpcS-I cpcU mutant strains was purified, and biochemical analyses showed that Cys-153 of CpcB carried a PCB chromophore but Cys-82 did not. These results show that both CpcS-I and CpcU are required for covalent attachment of PCB to Cys-82 of the PC ␤ subunit in this cyanobacterium. Suggesting that CpcS-I and CpcU are also required for attachment of PCB to allophycocyanin subunits in vivo, allophycocyanin levels were significantly reduced in all but the CpcV-less strain. These conclusions have been validated by in vitro experiments described in the accompanying report (Saunée, N. A., Williams, S. R., Bryant, D. A., and Schluchter, W. M. (2008) J. Biol. Chem. 283, 7513-7522). We conclude that the maturation of PBP in vivo depends on three PCB lyases: CpcE-CpcF, CpcS-I-CpcU, and CpcT.

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“…All rights reserved two (p-84 and p-155), numbered according to the positions of the binding cysteine residues [4,71. In situ, these heterohexamers or heterododecamers are aggregated with so-called linker peptides, which function as structural proteins, but are also important for energy transfer by fine tuning of the chromophore spectra [8-K?].…”

Section: C-phycocyaninmentioning

confidence: 99%

Dissociating effect of chromophore modifications on C-phycocyanin heterohexamers

Fischer

Scheer

1992

Journal of Photochemistry and Photobiology B: Biology

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The bilin chromophores of the a or /3 subunit of C-phycocyanin (PC) from Mastigocladus laminosus were modified, and subsequently recombined with the respective complementary unmodified chromophores. The modifications consisted of photobleaching (350 nm) or reversible reduction of the verdin-to rubin-type chromophore(s). Recombination led to heterodimers (a& but the heterohexameric aggregation state (a& could not be obtained with the modified chromophores. Autoxidation of the reduced a-84 chromophore in such a hybrid, which occurred on standing under aerobic conditions, induced reaggregation to heterohexamers. Chemical re-oxidation of the reduced chromophores did not produce reaggregation, and it was not promoted by a 22 kDa linker peptide fragment (Gottschalk et al., Photochem. Photobiol., 54 (1991) 283), which in unmodified samples stabilized heterohexameric aggregates. Binding of the mercurial p-chloromercury-benzenesulphonate to the single free cysteine of PC near (approximately 0.4 nm) the 884 chromophore had only a moderately destabilizing effect on the heterohexamer (a&. It was concluded that the intact chromophore structure is an important factor determining the quaternary structure of biliproteins. The tendency of heterohexamer destabilization is related to the situation in phycoerythrocyanin, where photoisomerization of the violobilin chromophore of the a subunit near the heterodimer-heterodimer contact region is also responsible for aggregate destabilization (Siebzehnriibl et al., Photochem. Photobiol., 46 (1989) 753).

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X-ray crystallographic structure of the light-harvesting biliprotein C-phycocyanin from the thermophilic cyanobacterium Mastigocladus laminosus and its resemblance to globin structures

Cited by 348 publications

References 59 publications

Biliprotein Chromophore Attachment

Biliprotein Chromophore Attachment

Biogenesis of Phycobiliproteins

Dissociating effect of chromophore modifications on C-phycocyanin heterohexamers

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