2j2f: Difference between revisions
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==Overview== | ==Overview== | ||
Sequence analysis of the diiron cluster-containing soluble desaturases, suggests they are unrelated to other diiron enzymes; however, structural, alignment of the core four-helix bundle of desaturases to other diiron, enzymes reveals a conserved iron binding motif with similar spacing in all, enzymes of this structural class, implying a common evolutionary ancestry., Detailed structural comparison of the castor desaturase with that of a, peroxidase, rubrerythrin, shows remarkable conservation of both identity, and geometry of residues surrounding the diiron center, with the exception, of residue 199. Position 199 is occupied by a threonine in the castor, desaturase, but the equivalent position in rubrerythrin contains a, glutamic acid. We previously hypothesized that a carboxylate in ... | Sequence analysis of the diiron cluster-containing soluble desaturases, suggests they are unrelated to other diiron enzymes; however, structural, alignment of the core four-helix bundle of desaturases to other diiron, enzymes reveals a conserved iron binding motif with similar spacing in all, enzymes of this structural class, implying a common evolutionary ancestry., Detailed structural comparison of the castor desaturase with that of a, peroxidase, rubrerythrin, shows remarkable conservation of both identity, and geometry of residues surrounding the diiron center, with the exception, of residue 199. Position 199 is occupied by a threonine in the castor, desaturase, but the equivalent position in rubrerythrin contains a, glutamic acid. We previously hypothesized that a carboxylate in this, location facilitates oxidase chemistry in rubrerythrin by the close, apposition of a residue capable of facilitating proton transfer to the, activated oxygen (in a hydrophobic cavity adjacent to the diiron center, based on the crystal structure of the oxygen-binding mimic azide). Here we, report that desaturase mutant T199D binds substrate but its desaturase, activity decreases by approximately 2 x 10(3)-fold. However, it shows a, >31-fold increase in peroxide-dependent oxidase activity with respect to, WT desaturase, as monitored by single-turnover stopped-flow spectrometry., A 2.65-A crystal structure of T199D reveals active-site geometry, remarkably similar to that of rubrerythrin, consistent with its enhanced, function as an oxidase enzyme. That a single amino acid substitution can, switch reactivity from desaturation to oxidation provides experimental, support for the hypothesis that the desaturase evolved from an ancestral, oxidase enzyme. | ||
==About this Structure== | ==About this Structure== | ||
2J2F is a | 2J2F is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Ricinus_communis Ricinus communis] with FE as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Transferred_entry:_1.14.19.2 Transferred entry: 1.14.19.2], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=1.14.99.6 1.14.99.6] Structure known Active Site: AC1. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=2J2F OCA]. | ||
==Reference== | ==Reference== | ||
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[[Category: transit peptide]] | [[Category: transit peptide]] | ||
''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on | ''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on Mon Nov 5 12:33:04 2007'' | ||
