CTB6_CERNC
ID CTB6_CERNC Reviewed; 357 AA.
AC A0ST44;
DT 12-SEP-2018, integrated into UniProtKB/Swiss-Prot.
DT 09-JAN-2007, sequence version 1.
DT 03-AUG-2022, entry version 46.
DE RecName: Full=Ketoreductase CTB6 {ECO:0000303|PubMed:17660442};
DE EC=1.-.-.- {ECO:0000305|PubMed:17660442};
DE AltName: Full=Cercosporin toxin biosynthesis cluster protein 6 {ECO:0000303|PubMed:17660442};
GN Name=CTB6 {ECO:0000303|PubMed:17660442};
OS Cercospora nicotianae (Barn spot disease fungus).
OC Eukaryota; Fungi; Dikarya; Ascomycota; Pezizomycotina; Dothideomycetes;
OC Dothideomycetidae; Mycosphaerellales; Mycosphaerellaceae; Cercospora.
OX NCBI_TaxID=29003;
RN [1]
RP NUCLEOTIDE SEQUENCE [GENOMIC DNA], FUNCTION, DISRUPTION PHENOTYPE, AND
RP PATHWAY.
RX PubMed=17660442; DOI=10.1099/mic.0.2007/007294-0;
RA Chen H.Q., Lee M.H., Chung K.R.;
RT "Functional characterization of three genes encoding putative
RT oxidoreductases required for cercosporin toxin biosynthesis in the fungus
RT Cercospora nicotianae.";
RL Microbiology (Mosc.) 153:2781-2790(2007).
RN [2]
RP NUCLEOTIDE SEQUENCE [GENOMIC DNA], FUNCTION, INDUCTION, AND PATHWAY.
RX PubMed=17462021; DOI=10.1111/j.1365-2958.2007.05689.x;
RA Chen H., Lee M.H., Daub M.E., Chung K.R.;
RT "Molecular analysis of the cercosporin biosynthetic gene cluster in
RT Cercospora nicotianae.";
RL Mol. Microbiol. 64:755-770(2007).
RN [3]
RP REVIEW ON CERCOSPORIN.
RX PubMed=11701851; DOI=10.1146/annurev.phyto.38.1.461;
RA Daub M.E., Ehrenshaft M.;
RT "The photoactivated cercospora toxin cercosporin: contributions to plant
RT disease and fundamental biology.";
RL Annu. Rev. Phytopathol. 38:461-490(2000).
RN [4]
RP FUNCTION.
RX PubMed=15915645; DOI=10.1094/mpmi-18-0468;
RA Choquer M., Dekkers K.L., Chen H.Q., Cao L., Ueng P.P., Daub M.E.,
RA Chung K.R.;
RT "The CTB1 gene encoding a fungal polyketide synthase is required for
RT cercosporin biosynthesis and fungal virulence of Cercospora nicotianae.";
RL Mol. Plant Microbe Interact. 18:468-476(2005).
RN [5]
RP FUNCTION.
RX PubMed=17074519; DOI=10.1016/j.fgb.2006.08.005;
RA Dekkers K.L., You B.J., Gowda V.S., Liao H.L., Lee M.H., Bau H.J.,
RA Ueng P.P., Chung K.R.;
RT "The Cercospora nicotianae gene encoding dual O-methyltransferase and FAD-
RT dependent monooxygenase domains mediates cercosporin toxin biosynthesis.";
RL Fungal Genet. Biol. 44:444-454(2007).
RN [6]
RP FUNCTION.
RX PubMed=23108075; DOI=10.1039/c2cc36010a;
RA Newman A.G., Vagstad A.L., Belecki K., Scheerer J.R., Townsend C.A.;
RT "Analysis of the cercosporin polyketide synthase CTB1 reveals a new fungal
RT thioesterase function.";
RL Chem. Commun. (Camb.) 48:11772-11774(2012).
RN [7]
RP FUNCTION, DISRUPTION PHENOTYPE, AND PATHWAY.
RX PubMed=26938470; DOI=10.1021/jacs.6b00633;
RA Newman A.G., Townsend C.A.;
RT "Molecular characterization of the cercosporin biosynthetic pathway in the
RT fungal plant pathogen Cercospora nicotianae.";
RL J. Am. Chem. Soc. 138:4219-4228(2016).
RN [8]
RP FUNCTION.
RX PubMed=30809363; DOI=10.1039/c8sc02870b;
RA Hu J., Sarrami F., Li H., Zhang G., Stubbs K.A., Lacey E., Stewart S.G.,
RA Karton A., Piggott A.M., Chooi Y.H.;
RT "Heterologous biosynthesis of elsinochrome A sheds light on the formation
RT of the photosensitive perylenequinone system.";
RL Chem. Sci. 10:1457-1465(2019).
CC -!- FUNCTION: Ketoreductase; part of the gene cluster that mediates the
CC biosynthesis of cercosporin, a light-activated, non-host-selective
CC toxin (PubMed:17074519, PubMed:15915645, PubMed:26938470). The
CC perylenequinone chromophore of cercosporin absorbs light energy to
CC attain an electronically-activated triplet state and produces active
CC oxygen species such as the hydroxyl radical, superoxide, hydrogen
CC peroxide or singlet oxygen upon reaction with oxygen molecules
CC (PubMed:11701851). These reactive oxygen species cause damage to
CC various cellular components including lipids, proteins and nucleic
CC acids (PubMed:11701851). The first step of cercosporin biosynthesis is
CC performed by the polyketide synthase CTB1 which catalyzes the formation
CC of nor-toralactone (PubMed:23108075, PubMed:26938470). The starter unit
CC acyltransferase (SAT) domain of CTB1 initiates polyketide extension by
CC the selective utilization of acetyl-CoA, which is elongated to the
CC heptaketide in the beta-ketoacyl synthase (KS) domain by successive
CC condensations with six malonyl units introduced by the malonyl
CC acyltransferase (MAT) domain. The product template (PT) domain
CC catalyzes C4-C9 and C2-C11 aldol cyclizations and dehydrations to a
CC trihydroxynaphthalene, which is thought to be delivered to the
CC thioesterase (TE) domain for product release (PubMed:23108075). The
CC bifunctional enzyme CTB3 then methylates nor-toralactone to toralactone
CC before conducting an unusual oxidative aromatic ring opening
CC (PubMed:17074519, PubMed:26938470). The O-methyltransferase CTB2
CC further methylates the nascent OH-6 of the CBT3 product, blocking
CC further oxidation at this site before the reductase CTB6 reduces the 2-
CC oxopropyl ketone at position C7, giving naphthalene (PubMed:17660442,
CC PubMed:26938470). The FAD-dependent monooxygenase CTB5 in concert with
CC the multicopper oxidase CTB12 are responsible for homodimerization of
CC naphthalene with CTB7 installing the dioxepine moiety, finally
CC producing cercosporin (PubMed:17660442, PubMed:30809363,
CC PubMed:26938470). The fasciclin domain-containing protein CTB11 might
CC act with CTB5 and CTB12 whereas the roles of CTB9 and CTB10 have still
CC to be elucidated (By similarity). {ECO:0000250|UniProtKB:Q0UHZ9,
CC ECO:0000269|PubMed:15915645, ECO:0000269|PubMed:17074519,
CC ECO:0000269|PubMed:17660442, ECO:0000269|PubMed:23108075,
CC ECO:0000269|PubMed:26938470, ECO:0000269|PubMed:30809363,
CC ECO:0000303|PubMed:11701851}.
CC -!- PATHWAY: Mycotoxin biosynthesis. {ECO:0000269|PubMed:17462021,
CC ECO:0000269|PubMed:17660442, ECO:0000269|PubMed:26938470}.
CC -!- INDUCTION: Expression is positively regulated by the cercosporin
CC cluster-specific transcription factor CTB8 (PubMed:17462021).
CC Expression is also affected by nitrogen and carbon sources and pH, and
CC is also controlled by another transcription activator, CRG1, previously
CC shown to regulate cercosporin production and resistance
CC (PubMed:17462021). {ECO:0000269|PubMed:17462021}.
CC -!- DISRUPTION PHENOTYPE: Abolishes the production of cercosporin but
CC accumulates the naphthoquinones called cercoquinone A and cercoquinone
CC B (PubMed:17660442, PubMed:26938470). Leads to dark orange-red mycelia
CC with significant export of colored compounds into the agar
CC (PubMed:26938470). {ECO:0000269|PubMed:17660442,
CC ECO:0000269|PubMed:26938470}.
CC -!- SIMILARITY: Belongs to the NAD(P)-dependent epimerase/dehydratase
CC family. Dihydroflavonol-4-reductase subfamily. {ECO:0000305}.
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DR EMBL; DQ991508; ABK64183.1; -; Genomic_DNA.
DR AlphaFoldDB; A0ST44; -.
DR SMR; A0ST44; -.
DR PHI-base; PHI:1047; -.
DR GO; GO:0016491; F:oxidoreductase activity; IEA:UniProtKB-KW.
DR InterPro; IPR001509; Epimerase_deHydtase.
DR InterPro; IPR036291; NAD(P)-bd_dom_sf.
DR Pfam; PF01370; Epimerase; 1.
DR SUPFAM; SSF51735; SSF51735; 1.
PE 2: Evidence at transcript level;
KW NADP; Oxidoreductase.
FT CHAIN 1..357
FT /note="Ketoreductase CTB6"
FT /id="PRO_0000444970"
FT BINDING 172
FT /ligand="NADP(+)"
FT /ligand_id="ChEBI:CHEBI:58349"
FT /evidence="ECO:0000250|UniProtKB:A0A059TC02"
SQ SEQUENCE 357 AA; 39489 MW; 163739EE47F94B85 CRC64;
MADSLVLLTG ATGFIGFRIL VELLRQGYSV RAVIRSAAKG QWLESRLTAV MKGSDYKDRF
QTTIVADFVT DGAFDQAAEN TSYIIHVASP IVSSDNPDDW EHDFKRVAVK GSIGVLEAAK
RSGTVRRVVI TSSMVGLFSP KALFAEPSEV PLNAESRIPE MEPPYAHKML AYQAGKIASI
NSAEAWIKHE KPAFDLIHMH PSFVTGRDDL ATTREDLRKF SSNWHSMQIV LGHKNPIGKP
ILTCHNDDVA RCHVSALDPK VAGNQSFLIS CSPEDGSEWD NVKKIVQREF PEAVAQGVLP
NDGHMPTVNK GVRFDVRKTE ETFGFKHIPY EAQVLDVVKQ YLELPEKDEG VEISTTA
