Proline biosynthesis gene proB of thermophilic bacterium Thermus ruber: Cloning, sequencing, and properties of encoded gamma-glutamylphosphate kinase

The proB gene of the thermophilic bacterium Thermus ruber was cloned and se quenced; and several properties of the encoded enzyme, gamma-glutamylphosph ate kinase (GPK), were studied. The proB open reading frame was 1170 nt. Nu cleotide sequence analysis revealed a GTG initiation codon at position 36 a nd a TGA termination codon at position 1304. The gene had 68% GC, as charac teristic of the genus Thermus. The deduced protein product had a molecular mass of 41,984 Da. The ProB amino acid sequence showed the highest homology (60%) to T. thermophilus GPK. The GPK activity was maximum (0.55 un./ml) a t 55-65 degrees C and weak at 70 degrees C. The enzyme can be used in biote chnological studies.