COMPLEMENTATION OF A PGK DELETION MUTATION IN SACCHAROMYCES-CEREVISIAE WITH EXPRESSION OF THE PHOSPHOGLYCERATE KINASE GENE FROM THE HYPERTHERMOPHILIC ARCHAEON SULFOLOBUS-SOLFATARICUS

The gene encoding phosphoglycerate kinase (PGK) from the Archaeon Sulf olobus solfataricus, an organism growing optimally at 87 degrees C, wa s inserted into a yeast expression vector under the control of the gal actose-inducible GAL1 yeast promoter. This vector was then transformed into a pgk::TRP1 yeast mutant, a strain inhibited for growth on galac tose or glucose due to its lack of PGK enzyme. Slow-growing transforma nts were obtained on galactose plates at 37 degrees C, but not 28 degr ees C. These transformants contained low levels of transcripts of the heterologous gene and low amounts of thermostable PGK activity. Weak e xpression of the hyperthermophile gene in yeast, a mesophile, therefor e enabled complementation of the yeast pgk defect at 37 degrees C but not at 28 degrees C.