Gene Ontology annotation through association of InterPro records with GO terms
Annotation inferences using phylogenetic trees
The oxygenase CAO-1 of Neurospora crassa is a resveratrol cleavage enzyme.
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CAO-1 does not cleave beta-carotene or any carotenoid/apocarotenoid tested; it is not a carotenoid cleavage enzyme.
"Here, we show that CAO-1 is not a carotenoid or apocarotenoid cleavage enzyme."
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CAO-1 cleaves the interphenyl double bond of resveratrol and piceatannol; expression is induced by resveratrol and is light-independent.
"adding resveratrol led to a pronounced increase in cao-1 mRNA levels, while light, a key regulator of carotenoid metabolism, did not alter them"
OpenScientist blinded function-assignment report for cao-1 (carotenoid dioxygenase activity, GO:0010436)
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An independent, blinded OpenScientist run neutrally tested whether CAO-1 has carotenoid dioxygenase activity and concluded it is refuted/over-annotated, recommending removal of the carotenoid IBA terms and retention of the experimentally supported dioxygenase MF - concurring with this review's REMOVE decision. It also attributed the error to CCO/RPE65 (PANTHER PTHR10543) family-level IBA propagation.
"Verdict: REFUTED (over-annotated)"
Structure-based analysis of CAO-1 stilbenoid substrate specificity (co-crystal H-bond network)
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A reproducible analysis of the CAO-1 co-crystal structures (5U90 resveratrol, 5U97 piceatannol) recovers the UniProt binding residues (Tyr133/Lys164, Glu383) and a two-ring-anchor recognition model (4'-OH -> Tyr133/Lys164; 3/5-OH -> Glu383; scissile alkene ~4.6 A from the metal) that explains all seven compounds of the empirical substrate panel - notably why a free 4'-OH is necessary but not sufficient (4-hydroxystilbene has it but lacks the second, ring-B anchor).
"The two-anchor model accounts for"
Structure and Spectroscopy of Alkene-Cleaving Dioxygenases Containing an Atypically Coordinated Non-Heme Iron Center.
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Crystal structure of CAO-1 shows a non-heme Fe center (four-His CCO motif) with a stilbenoid-adapted substrate-binding cleft; resveratrol and piceatannol bind in the active site.
"The crystal structure of a fungal stilbenoid-cleaving CCO, CAO1, reveals strong similarity between its iron center and those of carotenoid-cleaving CCOs, but with a markedly different substrate-binding cleft"