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Information on EC 7.2.1.3 - ascorbate ferrireductase (transmembrane) and Organism(s) Arabidopsis thaliana and UniProt Accession Q8L856

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IUBMB Comments
A diheme cytochrome that transfers electrons across a single membrane, such as the outer membrane of the enterocyte, or the tonoplast membrane of the plant cell vacuole. Acts on hexacyanoferrate(III) and other ferric chelates.
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Arabidopsis thaliana
UNIPROT: Q8L856
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The taxonomic range for the selected organisms is: Arabidopsis thaliana
The enzyme appears in selected viruses and cellular organisms
Synonyms
cytochrome b561, cytochrome b-559, dcytb, ferric chelate reductase, duodenal cytochrome b, cybrd1, cyt b561, cyb561, cyt-b561, lcytb, more
SYNONYM
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
cytochrome b561
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ascorbate-cytochrome b5 reductase
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cytochrome b561
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TCytb
REACTION
REACTION DIAGRAM
COMMENTARY hide
ORGANISM
UNIPROT
LITERATURE
ascorbate[side 1] + Fe(III)[side 2] = monodehydroascorbate[side 1] + Fe(II)[side 2]
show the reaction diagram
reaction mechanism
REACTION TYPE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
redox reaction
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oxidation
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reduction
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SYSTEMATIC NAME
IUBMB Comments
Fe(III):ascorbate oxidorectuctase (electron-translocating)
A diheme cytochrome that transfers electrons across a single membrane, such as the outer membrane of the enterocyte, or the tonoplast membrane of the plant cell vacuole. Acts on hexacyanoferrate(III) and other ferric chelates.
CAS REGISTRY NUMBER
COMMENTARY hide
37237-57-3
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SUBSTRATE
PRODUCT                       
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate) hide
LITERATURE
(Substrate)
COMMENTARY
(Product) hide
LITERATURE
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
ascorbate[side 1] + Fe(III)-citrate[side 2]
?
show the reaction diagram
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-
?
ascorbate[side 1] + Fe(III)-EDTA[side 2]
?
show the reaction diagram
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?
ascorbate[side 1] + Fe(III)[side 2]
monodehydroascorbate[side 1] + Fe(II)[side 2]
show the reaction diagram
ascorbate[side 1] + ferricyanide[side 2]
?
show the reaction diagram
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?
additional information
?
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structure-function relationship, overview
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?
NATURAL SUBSTRATE
NATURAL PRODUCT
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate) hide
LITERATURE
(Substrate)
COMMENTARY
(Product) hide
LITERATURE
(Product)
REVERSIBILITY
r=reversible
ir=irreversible
?=not specified
ascorbate[side 1] + Fe(III)[side 2]
monodehydroascorbate[side 1] + Fe(II)[side 2]
show the reaction diagram
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?
COFACTOR
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
ascorbate
cytosolic ascorbate is the cellular electron donor for the CYB561 proteins
cytochrome b561
a CYB561 protein
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heme
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TCytb possesses two hemes
heme b
two heme-b centers and CYB561 protein, structure analysis and comparisons, overview. Midpoint redox potentials, spin, and spectra of heme b, comparisons. The high-potential heme-b, characterized with a low-spin EPR signal in the vicinity of gz = 3.1, is located on the cytosolic side of the protein
pH OPTIMUM
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
additional information
the rate of reduction of CYB561 by ascorbate is only slightly pH-dependent, steady-state reduction kinetics
ORGANISM
COMMENTARY hide
LITERATURE
UNIPROT
SEQUENCE DB
SOURCE
LOCALIZATION
ORGANISM
UNIPROT
COMMENTARY hide
GeneOntology No.
LITERATURE
SOURCE
GENERAL INFORMATION
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
metabolism
enzyme is reduced by dihydrolipoic acid almost as efficiently as by ascorbate
evolution
the enzyme is a member of the CYB561 protein family
malfunction
mutation of His residues coordinating the intra-vesicular-side heme-b results in an almost complete loss of protein, while mutation of His residues coordinating the cytosolic-side heme-b hardly affects the expression of CYB561 proteins but results in a changed reducibility and heme content of these proteins
metabolism
oxidized Cyt b561 is reduced by ascorbate
physiological function
b-Type cytochromes are heme-containing, electron-transporting proteins in which the redox active center(s) is (are) iron-protoporphyrin(s) IX non-covalently bound to the protein matrix. Some of the b-type cytochromes are localized in membranous structures and have two heme-b prosthetic groups, the major function of these proteins is transmembrane electron transport. Plant rTCytb are capable of transporting electrons from cytosolic ASC to extracellular ferric chelates (ferricyanide, ferric-EDTA) in a yeast model system
additional information
the binding sites for the ascorbate on the cytoplasmic and the monodehydroascorbate on the non-cytoplasmic side do not correspond to the putative binding sites that had been inferred from the sequence (homology) analysis as well as from site directed mutagenesis of a number of CYB561 proteins. Models for the sidedness of CYB561 enzymes and the reduction by ascorbate, overview. The amino acid side chains contributing to the docking of ascorbate on the cytoplasmic surface of the crystallized protein (K77, K81, Y140, R150 and A151) do not constitute a single contiguous region but originate at distant locations of the primary sequence of the protein
UNIPROT
ENTRY NAME
ORGANISM
NO. OF AA
NO. OF TRANSM. HELICES
MOLECULAR WEIGHT[Da]
SOURCE
SEQUENCE
LOCALIZATION PREDICTION?
ACFR1_ARATH
239
6
25865
Swiss-Prot
Secretory Pathway (Reliability: 2)
SUBUNIT
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
additional information
Cytb561 enzyme structure analysis, structure-function relationship, detailed overview
CRYSTALLIZATION (Commentary)
ORGANISM
UNIPROT
LITERATURE
high-resolution crystal structures of cytochrome b561 from Arabidopsis thaliana in both substrate-free and substrate-bound states is reported. Cyt b561 forms a homodimer, with each protomer consisting of six transmembrane helices and two heme groups
PROTEIN VARIANTS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
F105W/H106E
mutations on the noncytoplasmic side only still allows the oxidized Cyt b561 to be reduced by ascorbate
H117A
site-directed mutagenesis, the mutation leads to reduced reduction of ascorbate by the mutant TCytb
H156A
site-directed mutagenesis, the mutation leads to reduced reduction of ascorbate by the mutant TCytb
H50A
site-directed mutagenesis, the mutation leads to reduced reduction of ascorbate by the mutant TCytb
H83A
site-directed mutagenesis, the mutation leads to reduced reduction of ascorbate by the mutant TCytb
H83A/H156A
site-directed mutagenesis
H83L/H156L
site-directed mutagenesis
K81A/R150A
mutations on the cytoplasmic side only still allows the oxidized Cyt b561 to be reduced by ascorbate
K81A/R150A/F105W/H106E
Y115W
mutations on the noncytoplasmic side only still allows the oxidized Cyt b561 to be reduced by ascorbate
Y140W
mutations on the cytoplasmic side only still allows the oxidized Cyt b561 to be reduced by ascorbate
PURIFICATION (Commentary)
ORGANISM
UNIPROT
LITERATURE
using Ni-NTA chromatography
purified by affinity chromatography and gel filtration
recombinant untagged four CYB561 isoforms from yeast YPH499 cells partially, two recombinant C-terminally His10- or Strep-II-tagged CYB561 paralogues from Escherichia coli and Pichia pastoris by affinity chromatography
CLONED (Commentary)
ORGANISM
UNIPROT
LITERATURE
expressed as a His-tagged fusion protein in Escherichia coli
cloning and recombinant expression of untagged four CYB561 isoforms in yeast YPH499 cells, recombinant expression of two C-terminally His10- or Strep-II-tagged CYB561 paralogues in either Escherichia coli or in Pichia pastoris. Functional expression of the enzyme in Saccharomyces cerevisiae strain S288C DELTAfre1DELTAfre2 deficient in ferric reductase activity
expressed in Escherichia coli
expressed in Saccharomyces cerevisiae, strain YPH499
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REF.
AUTHORS
TITLE
JOURNAL
VOL.
PAGES
YEAR
ORGANISM (UNIPROT)
PUBMED ID
SOURCE
Berczi, A.; Su, D.; Asard, H.
An Arabidopsis cytochrome b561 with trans-membrane ferrireductase capability
FEBS Lett.
581
1505-1508
2007
Arabidopsis thaliana
Manually annotated by BRENDA team
Berczi, A.; Zimanyi, L.; Asard, H.
Dihydrolipoic acid reduces cytochrome b561 proteins
Eur. Biophys. J.
42
159-168
2013
Arabidopsis thaliana (Q8L856), Mus musculus (Q9WUE3)
Manually annotated by BRENDA team
Lu, P.; Ma, D.; Yan, C.; Gong, X.; Du, M.; Shi, Y.
Structure and mechanism of a eukaryotic transmembrane ascorbate-dependent oxidoreductase
Proc. Natl. Acad. Sci. USA
111
1813-1818
2014
Arabidopsis thaliana (Q9SWS1), Arabidopsis thaliana
Manually annotated by BRENDA team
Berczi, A.; Zimanyi, L.
The trans-membrane cytochrome b561 proteins structural information and biological function
Curr. Protein Pept. Sci.
15
745-760
2014
Bos taurus (P10897), Homo sapiens (P49447), Schistosoma japonicum (Q5D8X4), Zea mays (Q6I681), Mus musculus (Q6P1H1), Arabidopsis thaliana (Q9SWS1)
Manually annotated by BRENDA team