Abstract
The genes proA and proB encoding the first 2 enzymes of the proline biosynthetic sequence (glutamate semialdehyde dehydrogenase EC 1.2.1.41 and .gamma.-glutamyl kinase EC 2.7.2.11, respectively) in E. coli were subcloned from a ColE1 hybrid plasmid containing 23.3 kilobases of genomic DNA. proA and proB are contiguous and constitute a single operon transcribed in the direction proB-proA. The pro operon is contiguous with the gene phoE. Hybridization experiments showed no homology between proAB of E. coli and the other regions of the E. coli genome or with the DNA of several other bacteria.