The dihydrofolate reductase-encoding gene dyrA of the hyperthermophilic bacterium Thermotoga maritima.

The structural gene (dyrA) encoding dihydrofolate reductase (DHFR) of Thermotoga maritima has been cloned, sequenced and expressed in Escherichia coli. The dyrA gene, located immediately upstream from the gene encoding aspartate carbamoyltransferase (pyrB), encodes a highly thermostable enzyme with a distinct thermophilic activity profile. Important structural features are conserved among all bacterial DHFR, yet the DHFR of T. maritima appears unique in a number of insertions and deletions, some of which are reminiscent of eukaryotic DHFR.