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'''CRYSTAL STRUCTURE OF E. COLI ORNITHINE TRANSCARBAMOYLASE COMPLEXED WITH NDELTA-L-ORNITHINE-DIAMINOPHOSPHINYL-N-SULPHONIC ACID (PSORN)''' | '''CRYSTAL STRUCTURE OF E. COLI ORNITHINE TRANSCARBAMOYLASE COMPLEXED WITH NDELTA-L-ORNITHINE-DIAMINOPHOSPHINYL-N-SULPHONIC ACID (PSORN)''' | ||
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[[Category: Mitchell, R E.]] | [[Category: Mitchell, R E.]] | ||
[[Category: Templeton, M D.]] | [[Category: Templeton, M D.]] | ||
[[Category: | [[Category: Enzyme-inhibitor complex]] | ||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 14:18:21 2008'' | |||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | |||
Revision as of 14:18, 2 May 2008
CRYSTAL STRUCTURE OF E. COLI ORNITHINE TRANSCARBAMOYLASE COMPLEXED WITH NDELTA-L-ORNITHINE-DIAMINOPHOSPHINYL-N-SULPHONIC ACID (PSORN)
OverviewOverview
The crystal structure is reported at 1.8 A resolution of Escherichia coli ornithine transcarbamoylase in complex with the active derivative of phaseolotoxin from Pseudomonas syringae pv. phaseolicola, N(delta)-(N'-sulfodiaminophosphinyl)-l-ornithine. Electron density reveals that the complex is not a covalent adduct as previously thought. Kinetic data confirm that N(delta)-(N'-sulfodiaminophosphinyl)-l-ornithine exhibits reversible inhibition with a half-life in the order of approximately 22 h and a dissociation constant of K(D) = 1.6 x 10(-12) m at 37 degrees C and pH 8.0. Observed hydrogen bonding about the chiral tetrahedral phosphorus of the inhibitor is consistent only with the presence of the R enantiomer. A strong interaction is also observed between Arg(57) Nepsilon and the P-N-S bridging nitrogen indicating that imino tautomers of N(delta)-(N'-sulfodiaminophosphinyl)-l-ornithine are present in the bound state. An imino tautomer of N(delta)-(N'-sulfodiaminophosphinyl)-l-ornithine is structurally analogous to the proposed reaction transition state. Hence, we propose that N(delta)-(N'-sulfodiaminophosphinyl)-l-ornithine, with its three unique N-P bonds, represents a true transition state analogue for ornithine transcarbamoylases, consistent with the tight binding kinetics observed.
About this StructureAbout this Structure
1DUV is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.
ReferenceReference
Mechanism of inactivation of ornithine transcarbamoylase by Ndelta -(N'-Sulfodiaminophosphinyl)-L-ornithine, a true transition state analogue? Crystal structure and implications for catalytic mechanism., Langley DB, Templeton MD, Fields BA, Mitchell RE, Collyer CA, J Biol Chem. 2000 Jun 30;275(26):20012-9. PMID:10747936 Page seeded by OCA on Fri May 2 14:18:21 2008