Premium
Electrostatic interactions across the dimer–dimer interface contribute to the pH‐dependent stability of a tetrameric malate dehydrogenase
Author(s) -
Bjørk Alexandra,
Mantzilas Dimitrios,
Sirevåg Reidun,
Eijsink Vincent G.H.
Publication year - 2003
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(03)01076-7
Subject(s) - dimer , malate dehydrogenase , mesophile , thermophile , chemistry , thermal stability , mutant , biochemistry , enzyme , biophysics , crystallography , biology , bacteria , organic chemistry , gene , genetics
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.