Molecular cloning and sequence analysis of the proC gene encoding delta 1-pyrroline-5-carboxylate reductase from an extremely thermophilic eubacterium Thermus thermophilus.

A gene library of the extremely thermophilic bacterium, Thermus thermophilus HB27, was constructed in Escherichia coli, and recombinant plasmids able to complement proC mutants of HB27 were obtained. Using the plasmids, the complete nucleotide sequence of the proC gene encoding delta 1-pyrroline-5-carboxylate reductase (P5CR) [EC 1.5.1.2] was determined. The deduced amino acid sequence showed a significant homology to those of P5CRs of E. coli, soybean and human. The proC gene of T. thermophilus was expressed in E. coli and the activity of heat-resistant P5CR was determined. The mutation sites of two HB27 proC mutants were also determined.