CTB3_CERNC
ID CTB3_CERNC Reviewed; 871 AA.
AC Q2I0M6;
DT 12-SEP-2018, integrated into UniProtKB/Swiss-Prot.
DT 02-MAY-2006, sequence version 2.
DT 03-AUG-2022, entry version 67.
DE RecName: Full=Dual O-methyltransferase/FAD-dependent monooxygenase CTB3 {ECO:0000303|PubMed:17074519};
DE AltName: Full=Cercosporin toxin biosynthesis cluster protein 3 {ECO:0000303|PubMed:17074519};
DE Includes:
DE RecName: Full=O-methyltransferase {ECO:0000303|PubMed:17074519};
DE EC=2.1.1.- {ECO:0000269|PubMed:26938470};
DE Includes:
DE RecName: Full=FAD-dependent monooxygenase {ECO:0000303|PubMed:17074519};
DE EC=1.-.-.- {ECO:0000269|PubMed:26938470};
GN Name=CTB3 {ECO:0000303|PubMed:17462021};
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, DOMAIN, DISRUPTION PHENOTYPE,
RP INDUCTION, AND PATHWAY.
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 [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=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 [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, CATALYTIC ACTIVITY, 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: Dual O-methyltransferase/FAD-dependent monooxygenase; part of
CC the gene cluster that mediates the biosynthesis of cercosporin, a
CC light-activated, non-host-selective toxin (PubMed:17074519,
CC PubMed:15915645, PubMed:26938470). The perylenequinone chromophore of
CC cercosporin absorbs light energy to attain an electronically-activated
CC triplet state and produces active oxygen species such as the hydroxyl
CC radical, superoxide, hydrogen peroxide or singlet oxygen upon reaction
CC with oxygen molecules (PubMed:11701851). These reactive oxygen species
CC cause damage to various cellular components including lipids, proteins
CC and nucleic acids (PubMed:11701851). The first step of cercosporin
CC biosynthesis is performed by the polyketide synthase CTB1 which
CC catalyzes the formation of nor-toralactone (PubMed:23108075,
CC PubMed:26938470). The starter unit acyltransferase (SAT) domain of CTB1
CC initiates polyketide extension by the selective utilization of acetyl-
CC CoA, which is elongated to the heptaketide in the beta-ketoacyl
CC synthase (KS) domain by successive condensations with six malonyl units
CC introduced by the malonyl acyltransferase (MAT) domain. The product
CC template (PT) domain catalyzes C4-C9 and C2-C11 aldol cyclizations and
CC dehydrations to a trihydroxynaphthalene, which is thought to be
CC delivered to the thioesterase (TE) domain for product release
CC (PubMed:23108075). The bifunctional enzyme CTB3 then methylates nor-
CC toralactone to toralactone before conducting an unusual oxidative
CC aromatic ring opening (PubMed:17074519, PubMed:26938470). The O-
CC methyltransferase CTB2 further methylates the nascent OH-6 of the CBT3
CC product, blocking further oxidation at this site before the reductase
CC CTB6 reduces the 2-oxopropyl ketone at position C7, giving naphthalene
CC (PubMed:17660442, PubMed:26938470). The FAD-dependent monooxygenase
CC CTB5 in concert with the multicopper oxidase CTB12 are responsible for
CC homodimerization of naphthalene with CTB7 installing the dioxepine
CC moiety, finally producing cercosporin (PubMed:17660442,
CC PubMed:30809363, PubMed:26938470). The fasciclin domain-containing
CC protein CTB11 might act with CTB5 and CTB12 whereas the roles of CTB9
CC and CTB10 have still to be elucidated (By similarity).
CC {ECO:0000250|UniProtKB:Q0UHZ9, ECO:0000269|PubMed:15915645,
CC ECO:0000269|PubMed:17074519, ECO:0000269|PubMed:17660442,
CC ECO:0000269|PubMed:23108075, ECO:0000269|PubMed:26938470,
CC ECO:0000269|PubMed:30809363, ECO:0000303|PubMed:11701851}.
CC -!- CATALYTIC ACTIVITY:
CC Reaction=nor-toralactone + S-adenosyl-L-methionine = H(+) + S-adenosyl-
CC L-homocysteine + toralactone; Xref=Rhea:RHEA:62908,
CC ChEBI:CHEBI:15378, ChEBI:CHEBI:57856, ChEBI:CHEBI:59789,
CC ChEBI:CHEBI:78029, ChEBI:CHEBI:146018;
CC Evidence={ECO:0000269|PubMed:26938470};
CC PhysiologicalDirection=left-to-right; Xref=Rhea:RHEA:62909;
CC Evidence={ECO:0000269|PubMed:26938470};
CC -!- CATALYTIC ACTIVITY:
CC Reaction=H(+) + NADH + O2 + toralactone = 1-(3,4,5-trihydroxy-7-
CC methoxynaphthalen-2-yl)propan-2-one + CO2 + NAD(+);
CC Xref=Rhea:RHEA:62912, ChEBI:CHEBI:15378, ChEBI:CHEBI:15379,
CC ChEBI:CHEBI:16526, ChEBI:CHEBI:57540, ChEBI:CHEBI:57945,
CC ChEBI:CHEBI:78029, ChEBI:CHEBI:146020;
CC Evidence={ECO:0000269|PubMed:26938470};
CC PhysiologicalDirection=left-to-right; Xref=Rhea:RHEA:62913;
CC Evidence={ECO:0000269|PubMed:26938470};
CC -!- PATHWAY: Mycotoxin biosynthesis. {ECO:0000269|PubMed:17074519,
CC ECO:0000269|PubMed:17462021, 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 naphthopyrones nor-toralactone and toralactone, as well
CC as the oxidation product of nor-toralactone, naphthoquinone
CC (PubMed:17074519, PubMed:26938470). Adopts a dark yellow-brown
CC coloration, with slight export of pigmented metabolites into the agar
CC (PubMed:26938470). {ECO:0000269|PubMed:17074519,
CC ECO:0000269|PubMed:26938470}.
CC -!- SIMILARITY: In the C-terminal section; belongs to the paxM FAD-
CC dependent monooxygenase family. {ECO:0000305}.
CC -!- SIMILARITY: In the N-terminal section; belongs to the class I-like SAM-
CC binding methyltransferase superfamily. Cation-independent O-
CC methyltransferase family. COMT subfamily. {ECO:0000305}.
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DR EMBL; DQ355149; ABC79591.2; -; Genomic_DNA.
DR AlphaFoldDB; Q2I0M6; -.
DR SMR; Q2I0M6; -.
DR PHI-base; PHI:1051; -.
DR GO; GO:0004497; F:monooxygenase activity; IEA:UniProtKB-KW.
DR GO; GO:0008171; F:O-methyltransferase activity; IEA:InterPro.
DR GO; GO:0032259; P:methylation; IEA:UniProtKB-KW.
DR Gene3D; 1.10.10.10; -; 1.
DR Gene3D; 3.40.50.150; -; 1.
DR Gene3D; 3.50.50.60; -; 1.
DR InterPro; IPR016461; COMT-like.
DR InterPro; IPR036188; FAD/NAD-bd_sf.
DR InterPro; IPR001077; O_MeTrfase_dom.
DR InterPro; IPR029063; SAM-dependent_MTases_sf.
DR InterPro; IPR036388; WH-like_DNA-bd_sf.
DR InterPro; IPR036390; WH_DNA-bd_sf.
DR Pfam; PF00891; Methyltransf_2; 1.
DR SUPFAM; SSF46785; SSF46785; 1.
DR SUPFAM; SSF51905; SSF51905; 1.
DR SUPFAM; SSF53335; SSF53335; 1.
DR PROSITE; PS51683; SAM_OMT_II; 1.
PE 1: Evidence at protein level;
KW FAD; Flavoprotein; Methyltransferase; Monooxygenase;
KW Multifunctional enzyme; NAD; Oxidoreductase; S-adenosyl-L-methionine;
KW Transferase.
FT CHAIN 1..871
FT /note="Dual O-methyltransferase/FAD-dependent monooxygenase
FT CTB3"
FT /id="PRO_0000444967"
FT REGION 1..429
FT /note="O-methyltransferase"
FT /evidence="ECO:0000269|PubMed:17074519"
FT REGION 430..871
FT /note="FAD-dependent monooxygenase"
FT /evidence="ECO:0000269|PubMed:17074519"
FT ACT_SITE 331
FT /note="Proton acceptor"
FT /evidence="ECO:0000255|PROSITE-ProRule:PRU01020"
FT BINDING 279
FT /ligand="S-adenosyl-L-methionine"
FT /ligand_id="ChEBI:CHEBI:59789"
FT /evidence="ECO:0000255|PROSITE-ProRule:PRU01020"
FT BINDING 485..488
FT /ligand="FAD"
FT /ligand_id="ChEBI:CHEBI:57692"
FT /evidence="ECO:0000250|UniProtKB:A6T923"
FT BINDING 617
FT /ligand="FAD"
FT /ligand_id="ChEBI:CHEBI:57692"
FT /evidence="ECO:0000250|UniProtKB:A6T923"
FT BINDING 627..631
FT /ligand="FAD"
FT /ligand_id="ChEBI:CHEBI:57692"
FT /evidence="ECO:0000250|UniProtKB:A6T923"
FT BINDING 681..683
FT /ligand="substrate"
FT /evidence="ECO:0000250|UniProtKB:A6T923"
FT BINDING 774..782
FT /ligand="FAD"
FT /ligand_id="ChEBI:CHEBI:57692"
FT /evidence="ECO:0000250|UniProtKB:A6T923"
SQ SEQUENCE 871 AA; 95728 MW; 7F7DD803CE5EE066 CRC64;
MMQFQRDLEA SLEAVSANAQ ELLKSLKSRK DVQDLNASLP KDPLDNCDAQ TQAARAQLAE
AATRILQLSI RPQEYLEHLQ NGYQHLTCFR WLVELNILDH LPHSGTISYT DLARKASVPP
MQLRSICRMA ICNGFLEEPE ANQVRHSRIS ALFARDESYL GWARWMVNYS VPAAYKLSDA
TRSWGETVAK DQTAFNLGMD VKVPFFDHLR QTPAMKDAFA AYMRNVTSNA TWGLQHAVTG
FDWASLPRGA KVVDVGGSLG HGSIAIAKEH THLTFVIQDL PETVAGARKE MAQNDKIEAS
VKSRITFQEH DFFGPQTVKD ADVYFLRMIC HDWPDNEAKV ILSQIRAALK PGAQIVIMDT
ILPQPGTISV LQEQQLRIRD LTMMEVFNAK ERELEDWSSL MQSAGLEISR VNQPLNSVMG
LLTVRSAGQT ALSGTNTLTP ELVAAVSAST GSADSRPVLI AGAGIAGLCL AQALKKAGID
FRVFERDSHI DARPQGYRLK FEADAAQSLK NILPDDVYEA FELSNAVTAV GETDFNPFNG
NIIHSRTGGG LSGKKGLYAT FTVDRKAFRT QLMTGIEDKI SFGKEIAYYK TDDATSTVNA
EFKDGTHVTG SFLAGTDGLH SVVRKTCVPN HRIVDTGAAC IYGKTVMTPE FLARFPEKGL
RFMTVVSDIA PMLQSCLIGD SPVTLLLEPI RFSEASRARY PELPPDYVYW ALIGPKERFG
SQEVTSMKNF VSLDQAAEQA AKLSLAVTEE WHPSLRALFE LQDTKQASLI RVASTIPDIP
SWESHSNVTV LGGSIHPMSP CGGVGANTAI VDADALAKVL VEHGTKPPVN AIAEFGAAMR
TRAKRNIWRS EVGSKRMFGQ KNLVDCSEFV F
