A mutation affecting the association equilibrium of formyltransferase from the hyperthermophilic Methanopyrus kandleri and its influence on the enzyme's activity and thermostability.

Formyltransferase from Methanopyrus kandleri is composed of only one type of subunit of molecular mass 32 kDa. The enzyme is in a monomer/dimer/tetramer association equilibrium, the association constant being affected by lyotropic salts. Oligomerization is required for enzyme activity and thermostability. We report here on a subunit interface mutation (R261E) which affects the dimer/tetramer part of the association equilibrium of formyltransferase. With the mutant protein it was shown that tetramerization is not required for activity but is necessary for high thermostability.