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| {{STRUCTURE_1w05| PDB=1w05 | SCENE= }} | | {{STRUCTURE_1w05| PDB=1w05 | SCENE= }} |
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| '''ISOPENICILLIN N SYNTHASE AMINOADIPOYL-CYSTEINYL-ALANINE-FE COMPLEX'''
| | ===ISOPENICILLIN N SYNTHASE AMINOADIPOYL-CYSTEINYL-ALANINE-FE COMPLEX=== |
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| ==Overview==
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| Isopenicillin N synthase (IPNS), a non-heme iron(II)-dependent oxidase, catalyzes conversion of the tripeptide delta-(l-alpha-aminoadipoyl)-l-cysteinyl-d-valine (ACV) to bicyclic isopenicillin N (IPN), concomitant with the reduction of dioxygen to two molecules of water. Incubation of the "truncated"substrate analogues delta-(l-alpha-aminoadipoyl)-l-cysteinyl-glycine (ACG) and delta-(l-alpha-aminoadipoyl)-l-cysteinyl-d-alanine (ACA) with IPNS has previously been shown to afford acyclic products, in which the substrate cysteinyl residue has undergone a two-electron oxidation. We report X-ray crystal structures for the anaerobic IPNS/Fe(II)/ACG and IPNS/Fe(II)/ACA complexes, both in the absence and presence of the dioxygen analogue nitric oxide. The overall protein structures are very similar to those of the corresponding IPNS/Fe(II)/ACV complexes; however, significant differences are apparent in the vicinity of the active site iron. The structure of the IPNS/Fe(II)/ACG complex reveals that the C-terminal carboxylate of this substrate is oriented toward the active site iron atom, apparently hydrogen-bonded to an additional water ligand at the metal; this is a different binding mode to that observed in the IPNS/Fe(II)/ACV complex. ACA binds to the metal in a manner that is intermediate between those observed for ACV and ACG. The addition of NO to these complexes initiates conformational changes such that both the IPNS/Fe(II)/ACG/NO and IPNS/Fe(II)/ACA/NO structures closely resemble the IPNS/Fe(II)/ACV/NO complex. These results further demonstrate the feasibility of metal-centered rearrangements in catalysis by non-heme iron enzymes and provide insight into the delicate balance between hydrophilic-hydrophobic interactions and steric effects in the IPNS active site.
| | The line below this paragraph, {{ABSTRACT_PUBMED_15850395}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 15850395 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_15850395}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Oxygenase]] | | [[Category: Oxygenase]] |
| [[Category: Penicillin biosynthesis]] | | [[Category: Penicillin biosynthesis]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 12:58:41 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 13:02:25 2008'' |