1h7k

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{{STRUCTURE_1h7k| PDB=1h7k | SCENE= }}
{{STRUCTURE_1h7k| PDB=1h7k | SCENE= }}
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'''FORMATION OF A TYROSYL RADICAL INTERMEDIATE IN PROTEUS MIRABILIS CATALASE BY DIRECTED MUTAGENESIS AND CONSEQUENCES FOR NUCLEOTIDE REACTIVITY'''
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===FORMATION OF A TYROSYL RADICAL INTERMEDIATE IN PROTEUS MIRABILIS CATALASE BY DIRECTED MUTAGENESIS AND CONSEQUENCES FOR NUCLEOTIDE REACTIVITY===
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==Overview==
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Proteus mirabilis catalase (PMC) belongs to the family of NADPH binding catalases. The function of NADPH in these enzymes is still a matter of debate. This study presents the effects of two independent phenylalanine mutations (F194 and F215), located between NADPH and heme in the PMC structure. The phenylalanines were replaced with tyrosines which we predicted could carry radicals in a NADPH-heme electron transfer. The X-ray crystal structures of the two mutants indicated that neither the binding site of NADPH nor the immediate environment of the residues was affected by the mutations. Measurements using H2O2 as a substrate confirmed that the variants were as active as the native enzyme. With equivalent amounts of peroxoacetic acid, wild-type PMC, F215Y PMC, and beef liver catalase (BLC) formed a stable compound I, while the F194Y PMC variant produced a compound I which was rapidly transformed into compound II and a tyrosyl radical. EPR studies showed that this radical, generated by the oxidation of Y194, was not related to the previously observed radical in BLC, located on Y369. In the presence of excess NADPH, compound I was reduced to a resting enzyme (k(obs) = 1.7 min(-1)) in a two-electron process. This was independent of the enzyme's origin and did not require any thus far identified tyrosyl radicals. Conversely, the presence of a tyrosyl radical in F194Y PMC greatly enhanced the oxidation of reduced beta-nicotinamide mononucleotide under a steady-state H2O2 flow with observable compound II. This process could involve a one-electron reduction of compound I via Y194.
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(as it appears on PubMed at http://www.pubmed.gov), where 11695923 is the PubMed ID number.
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{{ABSTRACT_PUBMED_11695923}}
==About this Structure==
==About this Structure==
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[[Category: Nadp]]
[[Category: Nadp]]
[[Category: Peroxidase]]
[[Category: Peroxidase]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 18:32:13 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 1 06:45:23 2008''

Revision as of 03:45, 1 July 2008

Image:1h7k.png

Template:STRUCTURE 1h7k

FORMATION OF A TYROSYL RADICAL INTERMEDIATE IN PROTEUS MIRABILIS CATALASE BY DIRECTED MUTAGENESIS AND CONSEQUENCES FOR NUCLEOTIDE REACTIVITY

Template:ABSTRACT PUBMED 11695923

About this Structure

1H7K is a Single protein structure of sequence from Proteus mirabilis. Full crystallographic information is available from OCA.

Reference

Formation of a tyrosyl radical intermediate in Proteus mirabilis catalase by directed mutagenesis and consequences for nucleotide reactivity., Andreoletti P, Gambarelli S, Sainz G, Stojanoff V, White C, Desfonds G, Gagnon J, Gaillard J, Jouve HM, Biochemistry. 2001 Nov 13;40(45):13734-43. PMID:11695923

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