2c6h: Difference between revisions

The pikromycin (Pik)/methymycin biosynthetic pathway of Streptomyces, venezuelae represents a valuable system for dissecting the fundamental, mechanisms of modular polyketide biosynthesis, aminodeoxysugar assembly, glycosyltransfer, and hydroxylation leading to the production of a series, of macrolide antibiotics, including the natural ketolides narbomycin and, pikromycin. In this study, we describe four x-ray crystal structures and, allied functional studies for PikC, the remarkable P450 monooxygenase, responsible for production of a number of related macrolide products from, the Pik pathway. The results provide important new insights into the, structural basis for the C10/C12 and C12/C14 hydroxylation patterns for, the 12-(YC-17) and 14-membered ring (narbomycin) macrolides, respectively., This includes two different ligand-free structures in an asymmetric unit, (resolution 2.1 A) and two co-crystal structures with bound endogenous, substrates YC-17 (resolution 2.35 A)or narbomycin (resolution 1.7 A). A, central feature of the enzyme-substrate interaction involves anchoring of, the desosamine residue in two alternative binding pockets based on a, series of distinct amino acid residues that form a salt bridge and a, hydrogen-bonding network with the deoxysugar C3' dimethylamino group., Functional significance of the salt bridge was corroborated by, site-directed mutagenesis that revealed a key role for Glu-94 in YC-17, binding and Glu-85 for narbomycin binding. Taken together, the x-ray, structure analysis, site-directed mutagenesis, and corresponding product, distribution studies reveal that PikC substrate tolerance and product, diversity result from a combination of alternative anchoring modes rather, than an induced fit mechanism.

2C6H is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Streptomyces_venezuelae Streptomyces venezuelae] with SO4, HEM and PXI as [http://en.wikipedia.org/wiki/ligands ligands]. Structure known Active Site: AC1. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=2C6H OCA].  

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