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°C to -26.8°C, and depended strongly on pH. Gel-filtration experiments indicated that the 26.8°C loss in stability observed for the D56K mutant at low pH was accompanied by a shift towards a lower oligomerization state. © 2003 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.
Bjørk, A., Mantzilas, D., Sirevåg, R., & Eijsink, V. G. H. (2003). Electrostatic interactions across the dimer-dimer interface contribute to the pH-dependent stability of a tetrameric malate dehydrogenase. FEBS Letters, 553(3), 423–426. https://doi.org/10.1016/S0014-5793(03)01076-7