MOLECULAR-CLONING AND EXPRESSION OF THE GLUCOSE XYLOSE ISOMERASE GENEFROM STREPTOMYCES SP NCIM-2730 IN ESCHERICHIA-COLI/

A partial genomic library of Streptomyces sp. NCIM 2730 was constructe d in Escherichia coli using pUC8 vector and screened for the presence of the D-glucose/xylose isomerase (GXI) gene using an Is-mer mixed oli gonucleotide probe complementary to a highly conserved six-amino acid sequence of GXI from actinomycetes. Eight clones which hybridized with the radiolabelled oligoprobe showed the ability to complement xylose isomerase-defective E. coli mutants. The restriction map of the insert from one (pMSG27) of the eight GXI-positive clones showing detectable GXI activity was constructed. GXI-deficient strains of E. coli were a ble to utilize xylose as the sole carbon source for their growth upon transformation with pMSG27. E. coli JM 105 (pMSG27) and E. coli JC1553 (pMSG27) were inducible by IPTG suggesting that the expression of the cloned gene was under the control of the lacZ promoter. Western blot analysis revealed that the cloned gene is expressed as a fusion protei n of M(r) 110. This is the first report of expression of a catalytical ly active GXI from Streptomyces in Escherichia coli.