Molecular characterization of mutations affecting expression level and growth rate-dependent regulation of the Escherichia coli zwf gene

We characterized three cis dominant mutations which elevate glucose 6-phosphate dehydrogenase level. Growth rate-dependent regulation and oxidative stress control of enzyme level were altered by the mutations. DNA sequencing and transcript mapping showed that the "up" mutations created new promoters whose hyperactive expression overrides the normal regulation of the native promoter.