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1yqo

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[[Image:1yqo.gif|left|200px]]
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{{Seed}}
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[[Image:1yqo.png|left|200px]]
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{{STRUCTURE_1yqo| PDB=1yqo | SCENE= }}
{{STRUCTURE_1yqo| PDB=1yqo | SCENE= }}
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'''T268A mutant heme domain of flavocytochrome P450 BM3'''
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===T268A mutant heme domain of flavocytochrome P450 BM3===
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==Overview==
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In flavocytochrome P450 BM3 there are several active site residues that are highly conserved throughout the P450 superfamily. Of these, a phenylalanine (Phe393) has been shown to modulate heme reduction potential through interactions with the implicitly conserved heme-ligand cysteine. In addition, a distal threonine (Thr268) has been implicated in a variety of roles including proton donation, oxygen activation and substrate recognition. Substrate binding in P450 BM3 causes a shift in the spin state from low- to high-spin. This change in spin-state is accompanied by a positive shift in the reduction potential (DeltaE(m) [WT+arachidonate (120 microM)]=+138 mV). Substitution of Thr268 by an alanine or asparagine residue causes a significant decrease in the ability of the enzyme to generate the high-spin complex via substrate binding and consequently leads to a decrease in the substrate-induced potential shift (DeltaE(m) [T268A+arachidonate (120 microM)]=+73 mV, DeltaE(m) [T268N+arachidonate (120 microM)]=+9 mV). Rate constants for the first electron transfer and for oxy-ferrous decay were measured by pre-steady-state stopped-flow kinetics and found to be almost entirely dependant on the heme reduction potential. More positive reduction potentials lead to enhanced rate constants for heme reduction and more stable oxy-ferrous species. In addition, substitutions of the threonine lead to an increase in the production of hydrogen peroxide in preference to hydroxylated product. These results suggest an important role for this active site threonine in substrate recognition and in maintaining an efficiently functioning enzyme. However, the dependence of the rate constants for oxy-ferrous decay on reduction potential raises some questions as to the importance of Thr268 in iron-oxo stabilisation.
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(as it appears on PubMed at http://www.pubmed.gov), where 16403573 is the PubMed ID number.
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{{ABSTRACT_PUBMED_16403573}}
==About this Structure==
==About this Structure==
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[[Category: Cytochrome p450]]
[[Category: Cytochrome p450]]
[[Category: Fatty acid hydroxylase]]
[[Category: Fatty acid hydroxylase]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 16:39:36 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun Jul 27 18:40:47 2008''

Revision as of 15:40, 27 July 2008

Image:1yqo.png

Template:STRUCTURE 1yqo

T268A mutant heme domain of flavocytochrome P450 BM3

Template:ABSTRACT PUBMED 16403573

About this Structure

1YQO is a Single protein structure of sequence from Bacillus megaterium. Full crystallographic information is available from OCA.

Reference

The role of Thr268 and Phe393 in cytochrome P450 BM3., Clark JP, Miles CS, Mowat CG, Walkinshaw MD, Reid GA, Daff SN, Chapman SK, J Inorg Biochem. 2006 May;100(5-6):1075-90. Epub 2006 Jan 5. PMID:16403573

Page seeded by OCA on Sun Jul 27 18:40:47 2008

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