CLONING, SEQUENCING AND ANALYSIS OF A GENE ENCODING ESCHERICHIA-COLI PROLINE DEHYDROGENASE

Using a genomic subtraction technique, we cloned a DNA sequence that i s present in wild-type Escherichia coli strain CSH4 but is missing in a presumptive proline dehydrogenase deletion mutant RM2. Experimental evidence indicated that the cloned fragment codes for proline dehydrog enase (EC 1.5.99.8) since RM2 cells transformed with a plasmid contain ing this sequence was able to survive on minimal medium supplemented w ith proline as the sole nitrogen and carbon sources. The cloned DNA fr agment has an open reading frame of 3942 bp and encodes a protein of 1 313 amino acids with a calculated M(r) of 143808. The deduced amino ac id sequence of the E. coli proline dehydrogenase has an 84.9% homology to the previously reported Salmonella typhimurium putA gene but it is 111 amino acids longer at the C-terminal than the latter.