Abstract
In an attempt to increase the thermostability of the neutral proteinase of Bacillus stearothermophilus the buried Ala-170 was replaced by serine. Molecular-dynamics simulations showed that Ser-170 stabilizes the enzyme by formation of an internal hydrogen bond. In addition, the hydroxy group of Ser-170 could contribute to stability by filling an internal cavity. After the introduction of the mutation, using site-directed-mutagenesis techniques, an increase in stability of 0.7 +/- 0.1 degrees C was obtained.