Analysis of the mutant proBA operon from a proline-producing strain of Serratia marcescens.
The nucleotide sequence of the proBA operon from a proline-hyperproducing mutant of Serratia marcescens was determined. Two base substitutions were found: one in the proB structural gene, coding for gamma-glutamyl kinase (GK), and a second one in the promoter region of the operon. The former base substitution led to a change of the predicted amino acid at position 117 from an alanine to a valine in GK. This mutation rendered GK 700-fold less sensitive to proline-mediated feedback inhibition than the wild-type enzyme. The other base substitution, a transversion from a G-C to an A-T, was located in the spacer region between the '-35' and '-10' sequences of the promoter, and it increased the transcriptional activity of this operon fourfold. Both these two base substitutions, which were acquired at the step of selecting mutants resistant to a toxic proline analogue, 3,4-dehydroproline, confer upon cells a high proline productivity and an increased osmotolerance.
Omori
K
K
Research Laboratory of Applied Biochemistry, Tanabe Seiyaku Co. Ltd., Osaka, Japan.
Suzuki
S
S
Imai
Y
Y
Komatsubara
S
S
D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D004352:Drug Resistance, Microbial; D005786:Gene Expression Regulation; D005798:Genes, Bacterial; D005822:Genetic Vectors; D008969:Molecular Sequence Data; D009154:Mutation; D009876:Operon; D010770:Phosphotransferases / Q000037:antagonists & inhibitors / Q000235:genetics; D017851:Phosphotransferases (Carboxyl Group Acceptor); D010957:Plasmids; D011392:Proline / Q000031:analogs & derivatives / Q000096:biosynthesis* / Q000235:genetics; D012706:Serratia marcescens / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism
D011392:Proline; D010770:Phosphotransferases; D017851:Phosphotransferases (Carboxyl Group Acceptor); C020650:glutamate 5-kinase