3i64 | pdb_00003i64
Crystal structure of an O-methyltransferase (NcsB1) from neocarzinostatin biosynthesis in complex with S-adenosyl-L-homocysteine (SAH) and 1,4-dihydroxy-2-naphthoic acid (DHN)
Structural highlights
FunctionNCSB1_STRCZ S-adenosyl-L-methionine-dependent O-methyltransferase that catalyzes regiospecific methylation at the 7-hydroxy group of 2,7-dihydroxy-5-methyl-1-naphthoate in the biosynthesis of the naphthoate moiety of the neocarzinostatin chromophore. Also recognizes other dihydroxynaphthoate as substrates and catalyzes their regiospecific O-methylation. The carboxylate and its ortho-hydroxy groups of the substrate appear to be crucial for NcsB1 substrate recognition and binding, and O-methylation takes place only at the free hydroxy group of these dihydroxynaphthoic acids.[1] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe small molecule component of the chromoprotein enediyne antitumor antibiotics is biosynthesized through a convergent route, incorporating amino acid, polyketide and carbohydrate building blocks around a central enediyne hydrocarbon core. The naphthoic acid moiety of the enediyne neocarzinostatin plays key roles in the biological activity of the natural product by interacting with both the carrier protein and duplex DNA at the site of action. We have previously described the in vitro characterization of an S-adenosylmethionine-dependent O-methyltransferase (NcsB1) in the neocarzinostatin biosynthetic pathway (Luo, Y.; Lin, S.; Zhang, J.; Cooke, H. A.; Bruner, S. D. and Shen, B. (2008) J. Biol. Chem. 283, 14694-14702). Here we provide a structural basis for NcsB1 activity, illustrating that the enzyme shares an overall architecture with a large family of S-adenosylmethionine-dependent proteins. In addition, NcsB1 represents the first enzyme to be structurally characterized in the biosynthetic pathway of neocarzinostatin. By co-crystallizing the enzyme with various combinations of the cofactor and substrate analogs, details of the active site structure have been established. Changes in subdomain orientation were observed by comparing structures in the presence and absence of substrate, suggesting that reorientation of the enzyme is involved in binding the substrate. In addition, residues important for substrate discrimination were predicted and probed through site directed mutagenesis and in vitro biochemical characterization. Molecular basis of substrate promiscuity for the SAM-dependent O-methyltransferase NcsB1, involved in the biosynthesis of the enediyne antitumor antibiotic neocarzinostatin.,Cooke HA, Guenther EL, Luo Y, Shen B, Bruner SD Biochemistry. 2009 Aug 25. PMID:19702337[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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