2e4g

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{{STRUCTURE_2e4g| PDB=2e4g | SCENE= }}
{{STRUCTURE_2e4g| PDB=2e4g | SCENE= }}
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'''RebH with bound L-Trp'''
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===RebH with bound L-Trp===
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==Overview==
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The flavin-dependent halogenase RebH catalyzes the formation of 7-chlorotryptophan as the initial step in the biosynthesis of antitumor agent rebeccamycin. The reaction of FADH2, Cl-, and O2 in the active site generates the powerful oxidant HOCl, which was presumed to carry out the chlorination reaction. Herein, we demonstrate the formation of a long-lived chlorinating intermediate (t1/2 = 63 h at 4 degrees C) when RebH, FADH2, Cl-, and O2 react in the absence of substrate tryptophan. This intermediate remained on the enzyme after removal of FAD and transferred chlorine to tryptophan with kinetically competent rates. The identity of this intermediate is suggested by the X-ray crystal structure of RebH, which revealed an active site Lys79 located in a central position between flavin and tryptophan binding sites and just 4.1 A above C7 of tryptophan. The chlorinating species is proposed to be a Lys-epsilonNH-Cl (lysine chloramine) from reaction of enzyme-generated HOCl with the active site Lys79. This covalent enzyme chloramine likely plays a key role in directing regiospecific chlorination of substrate in this important class of biosynthetic enzymes.
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(as it appears on PubMed at http://www.pubmed.gov), where 17260957 is the PubMed ID number.
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{{ABSTRACT_PUBMED_17260957}}
==About this Structure==
==About this Structure==
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[[Category: Rebeccamycin biosynthesis]]
[[Category: Rebeccamycin biosynthesis]]
[[Category: Tryptophan-7-halogenase]]
[[Category: Tryptophan-7-halogenase]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 03:30:25 2008''

Revision as of 00:30, 28 July 2008

Template:STRUCTURE 2e4g

RebH with bound L-Trp

Template:ABSTRACT PUBMED 17260957

About this Structure

2E4G is a Single protein structure of sequence from Lechevalieria aerocolonigenes. Full crystallographic information is available from OCA.

Reference

Chlorination by a long-lived intermediate in the mechanism of flavin-dependent halogenases., Yeh E, Blasiak LC, Koglin A, Drennan CL, Walsh CT, Biochemistry. 2007 Feb 6;46(5):1284-92. PMID:17260957

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