2ar8
From Proteopedia
The structure of tryptophan 7-halogenase (PrnA)suggests a mechanism for regioselective chlorination
Structural highlights
FunctionPRNA_PSEFL Involved in the biosynthesis of the antifungal antibiotic pyrrolnitrin. Catalyze the chlorination of tryptophan (Trp) at C7 position to yield 7-chloro-L-tryptophan (7-CLT). The reaction between FADH2, Cl-, and O2 generates the powerful oxidant HOCl, which is presumed to carry out the chlorination reaction. The reaction of HOCl with the active site Lys-79 generates a lysine chloramine, which plays a key role in directing regiospecific chlorination of substrate in this important class of biosynthetic enzymes. It is also able to use bromide ions to generate monobrominated Trp.[1] [2] [3] 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 PubMedChlorinated natural products include vancomycin and cryptophycin A. Their biosynthesis involves regioselective chlorination by flavin-dependent halogenases. We report the structural characterization of tryptophan 7-halogenase (PrnA), which regioselectively chlorinates tryptophan. Tryptophan and flavin adenine dinucleotide (FAD) are separated by a 10 angstrom-long tunnel and bound by distinct enzyme modules. The FAD module is conserved in halogenases and is related to flavin-dependent monooxygenases. On the basis of biochemical studies, crystal structures, and by analogy with monooxygenases, we predict that FADH2 reacts with O2 to make peroxyflavin, which is decomposed by Cl-. The resulting HOCl is guided through the tunnel to tryptophan, where it is activated to participate in electrophilic aromatic substitution. Tryptophan 7-halogenase (PrnA) structure suggests a mechanism for regioselective chlorination.,Dong C, Flecks S, Unversucht S, Haupt C, van Pee KH, Naismith JH Science. 2005 Sep 30;309(5744):2216-9. PMID:16195462[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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