Analysis of the mutant proBA operon from a proline-producing strain of Serratia marcescens

The mutant gene (pro BA) responsible for overproduction of proline in Serratia marsescens was sequenced and characterized. Sequence comparisons showed that the mutant contained two mutations, a G-C to A-T transversion at nucleotide 127 (Ppro 2) within the promoter region and a G-C to A-T transversion at nucleotide 531 (pro B1), which caused an alanine to valine substitution.. The pro B1 mutation caused an insensitivity to feedback inhibition by proline, while the Ppro 2 mutation caused an up-mutation in the promoter.