2X0R

R207S, R292S Mutant of Malate Dehydrogenase from the Halophilic Archeon Haloarcula marismortui (HoloForm)

Replaces:  1GT2

Summary for 2X0R

• Entry DOI: 10.2210/pdb2x0r/pdb
• Related: 1D3A 1HLP 1O6Z 2HLP 2J5K 2J5Q 2J5R
• Descriptor: MALATE DEHYDROGENASE, NICOTINAMIDE-ADENINE-DINUCLEOTIDE, CHLORIDE ION, ... (5 entities in total)
• Functional Keywords: protein-solvent interaction, haophilic, ion-binding, oxidoreductase, tricarboxylic acid cycle
• Biological source: HALOARCULA MARISMORTUI
• Total number of polymer chains: 2
• Total formula weight: 66978.60

Authors

Irimia, A.,Ebel, C.,Vellieux, F.M.D.,Richard, S.B.,Cosenza, L.W.,Zaccai, G.,Madern, D. (deposition date: 2009-12-17, release date: 2009-12-29, Last modification date: 2023-12-20)

Primary citation

Irimia, A.,Ebel, C.,Madern, D.,Richard, S.B.,Cosenza, L.W.,Zaccai, G.,Vellieux, F.M.D.
The Oligomeric States of Haloarcula Marismortui Malate Dehydrogenase are Modulated by Solvent Components as Shown by Crystallographic and Biochemical Studies
J.Mol.Biol., 326:859-873, 2003

PubMed Abstract: The three-dimensional crystal structure of the (R207S, R292S) mutant of malate dehydrogenase from Haloarcula marismortui was solved at 1.95A resolution in order to determine the role of salt bridges and solvent ions in halophilic adaptation and quaternary structure stability. The mutations, located at the dimer-dimer interface, disrupt two inter-dimeric salt bridge clusters that are essential for wild-type tetramer stabilisation. Previous experiments in solution, performed on the double mutant, had shown a tetrameric structure in 4M NaCl, which dissociated into active dimers in 2M NaCl. In order to establish if the active dimeric form is a product of the mutation, or if it also exists in the wild-type protein, complementary studies were performed on the wild-type enzyme by analytical centrifugation and small angle neutron scattering experiments. They showed the existence of active dimers in NaF, KF, Na(2)SO(4), even in the absence of NADH, and in the presence of NADH at concentrations of NaCl below 0.3M. The crystal structure shows a tetramer that, in the absence of the salt bridge clusters, appears to be stabilized by a network of ordered water molecules and by Cl(-) binding at the dimer-dimer interface. The double mutant and wild-type dimer folds are essentially identical (the r.m.s. deviation between equivalent C(alpha) positions is 0.39A). Chloride ions are also observed at the monomer-monomer interfaces of the mutant, contributing to the stability of each dimer against low salt dissociation. Our results support the hypothesis that extensive binding of water and salt is an important feature of adaptation to a halophilic environment.

PubMed: 12581646
DOI: 10.1016/S0022-2836(02)01450-X

Experimental method

X-RAY DIFFRACTION (2.915 Å)