PMID:15826651
| Citation |
Lee, M, Chan, CW, Mitchell Guss, J, Christopherson, RI and Maher, MJ (2005) Dihydroorotase from Escherichia coli: loop movement and cooperativity between subunits. J. Mol. Biol. 348:523-33 |
|---|---|
| Abstract |
Escherichia coli dihydroorotase has been crystallized in the presence of the product, L-dihydroorotate (L-DHO), and the structure refined at 1.9A resolution. The structure confirms that previously reported (PDB entry 1J79), crystallized in the presence of the substrate N-carbamyl-D,L-aspartate (D, L-CA-asp), which had a dimer in the asymmetric unit, with one subunit having the substrate, L-CA-asp bound at the active site and the other having L-DHO. Importantly, no explanation for the unusual structure was given. Our results now show that a loop comprised of residues 105-115 has different conformations in the two subunits. In the case of the L-CA-asp-bound subunit, this loop reaches in toward the active site and makes hydrogen-bonding contact with the bound substrate molecule. For the L-DHO-bound subunit, the loop faces in the opposite direction and forms part of the surface of the protein. Analysis of the kinetics for conversion of L-DHO to L-CA-asp at low concentrations of L-DHO shows positive cooperativity with a Hill coefficient n=1.57(+/-0.13). Communication between subunits in the dimer may occur via cooperative conformational changes of the side-chains of a tripeptide from each subunit: Arg256-His257-Arg258, near the subunit interface. |
| Links |
PubMed Online version:10.1016/j.jmb.2005.01.067 |
| Keywords |
Amino Acid Sequence; Animals; Binding Sites; Crystallography, X-Ray; Dihydroorotase/chemistry; Dihydroorotase/metabolism; Escherichia coli Proteins/chemistry; Escherichia coli Proteins/metabolism; Humans; Models, Molecular; Molecular Sequence Data; Molecular Structure; Orotic Acid/analogs & derivatives; Orotic Acid/metabolism; Protein Binding; Protein Structure, Quaternary; Protein Structure, Tertiary; Protein Subunits/chemistry; Protein Subunits/metabolism; Sequence Alignment |
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