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Electrostatic interactions across the dimer-dimer interface contribute to the pH-dependent stability of a tetrameric malate dehydrogenase.

Alexandra Bjørk·Dimitrios Mantzilas·Reidun Sirevåg·Vincent G H Eijsink
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Abstract

Malate dehydrogenase (MDH) from the moderately thermophilic bacterium Chloroflexus aurantiacus (CaMDH) is a tetrameric enzyme, while MDHs from mesophilic bacteria usually are dimers. Using site-directed mutagenesis, we show here that a network of electrostatic interactions across the extra dimer-dimer interface in CaMDH is important for thermal stability and oligomeric integrity. Stability effects of single point mutations (E25Q, E25K, D56N, D56K) varied from -1.2 degrees C to -26.8 degrees C, and depended strongly on pH. Gel-filtration experiments indicated that the 26.8 degrees C loss in stability observed for the D56K mutant at low pH was accompanied by a shift towards a lower oligomerization state.

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Amino Acid SubstitutionBacterial ProteinsChlorobiChromatography, GelDimerizationEnzyme StabilityHot TemperatureHydrogen-Ion ConcentrationMalate DehydrogenaseModels, MolecularMutagenesis, Site-DirectedProtein ConformationProtein DenaturationProtein Structure, QuaternaryProtein SubunitsRecombinant ProteinsStatic ElectricityTemperatureJournal ArticleResearch Support, Non-U.S. Gov't

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Alexandra Bjørk, Dimitrios Mantzilas, Reidun Sirevåg, Vincent G H Eijsink. 2003-10-23. Electrostatic interactions across the dimer-dimer interface contribute to the pH-dependent stability of a tetrameric malate dehydrogenase.. https://doi.org/10.1016/s0014-5793(03)01076-7

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