3I53: Crystal Structure Of An O-Methyltransferase (Ncsb1) From Neocarzinostatin Biosynthesis In Complex With S-Adenosyl-L- Homocysteine (Sah)

Citation:
Abstract
The small molecule component of 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 cocrystallizing the enzyme with various combinations of the cofactor and substrate analogues, details of the active site structure have been established. Changes in subdomain orientation were observed via comparison of structures in the presence and absence of substrate, suggesting that reorientation of the enzyme is involved in binding of the substrate. In addition, residues important for substrate discrimination were predicted and probed through site-directed mutagenesis and in vitro biochemical characterization.
PDB ID: 3I53Download
MMDB ID: 76480
PDB Deposition Date: 2009/7/3
Updated in MMDB: 2009/10
Experimental Method:
x-ray diffraction
Resolution: 2.08  Å
Source Organism:
Similar Structures:
Biological Unit for 3I53: dimeric; determined by author and by software (PISA)
Molecular Components in 3I53
Label Count Molecule
Proteins (2 molecules)
2
O-methyltransferase
Molecule annotation
Chemicals (3 molecules)
1
2
2
1
* Click molecule labels to explore molecular sequence information.

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