6b86 | pdb_00006b86
2.2A Crystal Structure of Co-CAO1
Structural highlights
Publication Abstract from PubMedCarotenoid cleavage oxygenases (CCO) are non-heme iron enzymes that catalyze oxidative cleavage of alkene bonds in carotenoid and stilbenoid substrates. Previously, we showed that the iron cofactor of CAO1, a resveratrol-cleaving member of this family, can be substituted with cobalt to yield a catalytically inert enzyme useful for trapping active site-bound stilbenoid substrates for structural characterization. Metal substitution may provide a general method for identifying the natural substrates for CCOs in addition to facilitating structural and biophysical characterization of CCO-carotenoid complexes under normal aerobic conditions. Here, we demonstrate the general applicability of cobalt substitution in a prototypical carotenoid cleaving CCO, apocarotenoid oxygenase (ACO) from Synechocystis. Among the non-native divalent metals investigated, cobalt was uniquely able to stably occupy the ACO metal binding site and inhibit catalysis. Analysis by X-ray crystallography and X-ray absorption spectroscopy demonstrate that the Co(II) forms of both ACO and CAO1 exhibit a close structural correspondence to the native Fe(II) enzyme forms. Hence, cobalt substitution is an effective strategy for generating catalytically inert but structurally intact forms of CCOs. Preparation and characterization of metal-substituted carotenoid cleavage oxygenases.,Sui X, Farquhar ER, Hill HE, von Lintig J, Shi W, Kiser PD J Biol Inorg Chem. 2018 Aug;23(6):887-901. doi: 10.1007/s00775-018-1586-0. Epub, 2018 Jun 26. PMID:29946976[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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