Gene Ontology annotation through association of InterPro records with GO terms
Gene Ontology annotation based on UniPathway vocabulary mapping
Directed mutational analysis of bacteriochlorophyll a biosynthesis in Rhodobacter capsulatus.
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A systematic directed mutational analysis of 12 open reading frames of the Rhodobacter capsulatus photosynthesis gene cluster, scoring each for loss of photopigment biosynthesis and for accumulation of Mg-tetrapyrrole intermediates. Seven mutants lost bacteriochlorophyll biosynthesis outright, one was partially disrupted and accumulated both bacteriochlorophyll and an intermediate, and four had no discernible pigment phenotype.
"In this study we have undertaken a systematic directed mutational analysis of 12 open reading frames in the photosynthesis gene cluster to evaluate whether individual open reading frames have a role in photopigment biosynthesis."
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One of the twelve mutants showed partial rather than complete disruption of bacteriochlorophyll biosynthesis, accumulating bacteriochlorophyll together with a pathway intermediate. This is the phenotype later characterised for bchJ in PMID:7876113, but the abstract does not name the gene and the full text is not in the cache, so the identification is an inference.
"One mutation was observed to result in partial disruption of bacteriochlorophyll biosynthesis, leading to the accumulation of bacteriochlorophyll as well as an intermediate in the biosynthetic pathway."
Altered monovinyl and divinyl protochlorophyllide pools in bchJ mutants of Rhodobacter capsulatus. Possible monovinyl substrate discrimination of light-independent protochlorophyllide reductase.
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Directed insertion and deletion mutations in R. capsulatus bchJ reduce bacteriochlorophyll levels and cause accumulation of divinyl protochlorophyllide, skewing the monovinyl:divinyl ratio of the pathway intermediate pool.
"bchJ-disrupted strains accumulate reduced levels of bacteriochlorophyll concomitant with the accumulation of divinyl protochlorophyllide"
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The authors read the altered monovinyl:divinyl ratio as identifying bchJ as the gene responsible for divinyl-to-monovinyl conversion, the basis of the later 4-vinyl / C8-vinyl reductase designation. This interpretation has been superseded: the reduction is catalysed by BciA, BciB and, in Rhodobacter, by chlorophyllide a oxidoreductase, and bchJ mutants in two other species still make C8-ethyl pigment.
"These results thus identify bchJ as the first sequenced gene that affects the divinyl to monovinyl ratio of photopigment intermediates in any photosynthetic organism."
Characterization of a plant-like protochlorophyllide a divinyl reductase in green sulfur bacteria.
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Insertional inactivation of both candidate genes in Chlorobium tepidum assigns C-8 divinyl reductase activity to CT1063 (renamed bciA) and not to bchJ; recombinant BciA reduces the C-8 vinyl group of 3,8-divinyl-protochlorophyllide in vitro using NADPH.
"These data demonstrate that CT1063, renamed bciA, encodes a C-8 divinyl reductase in C. tepidum."
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The C. tepidum bchJ mutant still makes C-8-reduced chlorophyll and bacteriochlorophylls while secreting divinyl protochlorophyllide, so BchJ cannot be the reductase; the authors propose substrate channelling or regulation instead.
"The bchJ mutant produces detectable amounts of Chl a(PD), BChl a(P), and BChl c(F), all of which have reduced C-8 substituents, but the mutant cells secrete large amounts of 3,8-divinyl-protochlorophyllide a into the growth medium and have a greatly reduced BChl c(F) content."
Identification of an 8-vinyl reductase involved in bacteriochlorophyll biosynthesis in Rhodobacter sphaeroides and evidence for the existence of a third distinct class of the enzyme.
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In Rhodobacter sphaeroides, deletion of bchJ and/or rsp_3070 still leaves C8-ethyl bacteriochlorophyll synthesis intact, and in a cyanobacterial C8-vinyl reductase mutant rsp_3070 restores wild-type C8-ethyl chlorophyll a whereas bchJ does not. The authors conclude there is no direct evidence that BchJ is a C8-vinyl reductase.
"R. sphaeroides rsp_3070 was able to restore synthesis of the WT (wild-type) C8-ethyl chlorophyll a in the mutant, whereas bchJ did not."
Rhodobacter sphaeroides mutants overexpressing chlorophyllide a oxidoreductase of Blastochloris viridis elucidate functions of enzymes in late bacteriochlorophyll biosynthetic pathways.
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Pathway membership for BchJ is not in dispute even though the mechanism is: the authors state plainly that BchJ is involved in bacteriochlorophyll biosynthesis by an unclear route, and that its function has been enigmatic since the vinyl-reductase assignment lapsed.
"BchJ is known to be involved in BChl biosynthesis, although how is still unclear."
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An exogenous Blastochloris viridis BchYZ competes on equal terms with the intrinsic Rhodobacter COR only when BchJ is absent, which the authors read as BchJ raising the effective catalytic throughput of the intrinsic enzyme; whether that is carriage, scaffolding or chaperoning is left open.
"These results from the two mutants suggest that BchJ in R. sphaeroides facilitates the catalytic activity of only the intrinsic a-COR."
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In Rhodobacter the 8-vinyl reduction is carried by chlorophyllide a oxidoreductase, which is why deleting bciA and bchJ does not abolish C8-ethyl pigment.
"This suggests that the intrinsic a-COR present in the double mutant works as DVR"
BchJ and BchM interact in a 1 : 1 ratio with the magnesium chelatase BchH subunit of Rhodobacter capsulatus.
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Purified recombinant Rhodobacter capsulatus BchJ binds Mg-protoporphyrin IX and forms a ternary complex with it and the magnesium chelatase BchH subunit, shifting the equilibrium amount of Mg-protoporphyrin IX in a chelatase assay in a 1:1 ratio with BchH.
"BchJ bound magnesium-protoporphyrin IX or formed a ternary complex with BchH and magnesium-protoporphyrin IX."
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The authors propose BchJ as a general magnesium porphyrin carrier, a bacterial counterpart of one role of plant GUN4, noting that BchJ has no assigned function in the established pathway.
"These results suggest that BchJ may play a role as a general magnesium porphyrin carrier, similar to one of the roles of GUN4 in oxygenic organisms."
UniProtKB P26169 (BCHJ_RHOCB) flat file
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UniProt curates the entry's pathway as light-independent bacteriochlorophyll biosynthesis within porphyrin-containing compound metabolism, and assigns it the BchJ-specific family signatures NCBIfam TIGR02019 and InterPro IPR010249 together with a single V4R domain (Pfam PF02830).
"PATHWAY: Porphyrin-containing compound metabolism; bacteriochlorophyll biosynthesis (light-independent)."