TY - JOUR
T1 - Dihydroorotase from Escherichia coli: Loop Movement and Cooperativity between Subunits
AU - Lee, Mihwa
AU - Chan, C.W.
AU - Guss, J.M.
AU - Christopherson, R.I.
AU - Maher, M.J.
PY - 2005
Y1 - 2005
N2 - Escherichia coli dihydroorotase has been crystallized in the presence of the product, L-dihydroorotate (L-DHO), and the structure refined at 1.9 angstrom resolution. The structure confirms that previously reported (PDB entry 1]79), 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-aspbound subunit, this loop reaches in toward the active site and makes hydrogen-bonding contact with the bound substrate molecule. For the LDHO-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. (c) 2005 Elsevier Ltd. All rights reserved.
AB - Escherichia coli dihydroorotase has been crystallized in the presence of the product, L-dihydroorotate (L-DHO), and the structure refined at 1.9 angstrom resolution. The structure confirms that previously reported (PDB entry 1]79), 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-aspbound subunit, this loop reaches in toward the active site and makes hydrogen-bonding contact with the bound substrate molecule. For the LDHO-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. (c) 2005 Elsevier Ltd. All rights reserved.
U2 - 10.1016/j.jmb.2005.01.067
DO - 10.1016/j.jmb.2005.01.067
M3 - Article
C2 - 15826651
SN - 0022-2836
VL - 348
SP - 523
EP - 533
JO - Journal of Molecular Biology
JF - Journal of Molecular Biology
IS - 3
ER -