Biliprotein Chromophore Attachment

Böhm, Stephan; Endres, Stefanie; Scheer, Hugo; Zhao, Kai‐Hong

doi:10.1074/jbc.m702669200

Cited by 25 publications

(15 citation statements)

References 66 publications

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“…Subsequent bilin attachment to phycobiliproteins is in most cases supported by members of the three known phycobiliprotein lyase families (E/F, S/U, and T) (6). These proteins are supposed to guide the reaction in a chaperone-like manner probably by conformational control of the bilin (7,8). In addition, some lyases act as isomerases and generate phycoviolobilin or phycourobilin upon attachment to the phycobiliprotein (9 -11).…”

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confidence: 99%

CpeS Is a Lyase Specific for Attachment of 3Z-PEB to Cys82 of β-phycoerythrin from Prochlorococcus marinus MED4

Wiethaus

Busch

Kock

et al. 2010

Journal of Biological Chemistry

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In contrast to the majority of cyanobacteria, the unicellular marine cyanobacterium Prochlorococcus marinus MED4 uses an intrinsic divinyl-chlorophyll-dependent light-harvesting system for photosynthesis. Despite the absence of phycobilisomes, this high-light adapted strain possesses ␤-phycoerythrin (CpeB), an S-type lyase (CpeS), and enzymes for the biosynthesis of phycoerythrobilin (PEB) and phycocyanobilin. Of all linear tetrapyrroles synthesized by Prochlorococcus including their 3Z-and 3E-isomers, CpeS binds both isomers of PEB and its biosynthetic precursor 15,16-dihydrobiliverdin (DHBV). However, dimerization of CpeS is independent of bilins, which are tightly bound in a complex at a ratio of 1:1. Although bilin binding by CpeS is fast, transfer to CpeB is rather slow. CpeS is able to attach 3E-PEB and 3Z-PEB to dimeric CpeB but not DHBV. CpeS transfer of 3Z-PEB exclusively yields correctly bound ␤Cys 82 -PEB, whereas ␤Cys 82 -DHBV is a side product of 3E-PEB transfer. Spontaneous 3E-and 3Z-PEB addition to CpeB is faulty, and products are in both cases ␤Cys 82 -DHBV and likely a PEB bound at ␤Cys 82 in a non-native configuration. Our data indicate that CpeS is specific for 3Z-PEB transfer to ␤Cys 82 of phycoerythrin and essential for the correct configuration of the attachment product.

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CpeS Is a Lyase Specific for Attachment of 3Z-PEB to Cys82 of β-phycoerythrin from Prochlorococcus marinus MED4

Wiethaus

Busch

Kock

et al. 2010

Journal of Biological Chemistry

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“…This is a clear indication that the function of CpcS1 is not catalytic in the classic enzymological sense of speeding up the reaction, but rather chaperone-like to control the correct attachment. A chaperone-like action had already been demonstrated for an E/F-type bilin lyase (18), suggesting similar functions for these phylogenetically unrelated lyases, which also have very different secondary structures. Further, a chaperonelike action has also been demonstrated for another tetrapyrrole-attaching enzyme, the cytochrome c lyase (58).…”

Section: Discussionmentioning

confidence: 99%

“…This sequence has now been confirmed and extended by a combination of time-resolved spectroscopy and site-directed mutagenesis. The only biliprotein lyases that had previously been characterized mechanistically in some detail are of the E/F-type (7,17,18). In the following discussion, these two types will be compared with each other and with the phytochromes and the related cyano(bacterio)chromes that bind bilin chromophores autocatalytically (24,(45)(46)(47).…”

Section: Discussionmentioning

confidence: 99%

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Catalytic Mechanism of S-type Phycobiliprotein Lyase

Kupka¹,

Zhang

et al. 2009

Journal of Biological Chemistry

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We now show that CpcS1 binds PCB and PEB rapidly with bi-exponential kinetics (38/119 and 12/8300 ms, respectively). Chromophore binding to the lyase is reversible and much faster than the spontaneous, but low fidelity chromophore addition to the apo-protein in the absence of the lyase. This indicates kinetic control by the enzyme, which then transfers the chromophore to the apo-protein in a slow (tens of minutes) but stereo-and regioselectively corrects the reaction. This mode of action is reminiscent of chaperones but does not require ATP. The amino acid residues Arg-18 and Arg-149 of the lyase are essential for chromophore attachment in vitro and in Escherichia coli, mutations of His-21, His-22, Trp-75, Trp-140, and Arg-147 result in reduced activity (<30% of wild type in vitro). Mutants R147Q and W69M were active but had reduced capacity for PCB binding; additionally, with W69M there was loss of fidelity in chromophore attachment. Imidazole is a noncompetitive inhibitor, supporting a bilin-binding function of histidine. Evidence was obtained that CpcS1 also catalyzes exchange of C-␤84-bound PCB in biliproteins by PEB.Phycobiliproteins are a homologous family of light-harvesting proteins present in cyanobacteria, red algae, and cryptophytes that absorb light in the spectral region between the chlorophyll absorption maxima at ϳ430 and ϳ680 nm: they contain linear tetrapyrroles (phycobilins) of which 1-4 are covalently attached to the subunits by thioether bonds to conserved cysteines (1-4). The chromophores are derived from heme by oxidative ring-opening and subsequent reduction (5) and then attached post-translationally. The correct attachment of most chromophores is catalyzed by lyases. Three phylogenetically unrelated types of lyases have been characterized in cyanobacteria (6). They are specific for certain binding sites and chromophores (7-16), but the reaction mechanisms are still unclear. A chaperone-like action has been proposed for E/Ftype lyases that catalyze chromophore attachment to Cys-84 of ␤-subunits of phyco(erythro)cyanins (17, 18). A more highly evolved function is suggested, however, by concomitant isomerizing reactions catalyzed by certain lyases (12,19,20), and by the finding that most lyases can bind the chromophore and then transfer it to the acceptor protein (15,21).Chromophore binding is particularly pronounced with the S-type lyases. CpcS1 from Nostoc PCC7120 6 rapidly forms an adduct with phycocyanobilin (PCB), 7 and the latter can be transferred in a much slower reaction to cysteine 84 of the ␤-subunits of phycocyanin (CpcB) or phycoerythrocyanin (PecB), suggesting that PCB-CpcS1 is an intermediate of the enzymatic reaction (21). Model reactions of PCB with nucleophiles resulted in the formation of addition products in which the chromophore is isomerized and which are also substrates for a CpcS1-catalzed chromophore transfer to the apo-proteins (20). We now report chromophore binding kinetics obtained by stopped-flow techniques, and identification of functional amino acid residues f...

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“…Individual CpcE and CpcF subunits usually exhibit low levels of ligation activity when assayed separately (5,21). For example, compared with PecE/PecF together, PecE from Mastigocladus laminosus had 10% PCB ligation activity on PecA (64). RpcG is also a larger bilin lyase that appears to have resulted from a fusion of genes encoding RpcE and RpcF (25); RpcG is involved in PEB chromophore ligation and isomerization to phycourobilin on RpcA (26).…”

Section: Discussionmentioning

confidence: 99%