Abstract:
Glucose isomerase gene from Streptomyces sp.190-1 was cloned in Escherichia coli HB101 by using pUC18 or pUC19 as cloning vector. Ampicillin resistant transformants were selected on MacConkey agar base medium containing xylose as an inducer. One stable positive clone, namely clone 289, showing red colony which indicated the presence of glucose isomerase gene was obtained. The recombinant plasmid was designated as pUR289. Glucose isomerase activity of E. coli HB101 harboring pUR289 or pUC18 when cultivated in LB medium containing xylose were 27.9 and 11.0 nmol/min/mg of protein respectively. When E. coli HB101 harboring pUR289 was induced with IPTG, the specific activity of glucose isomerase was 33.3 nmol/min/mg of protein. Size of the DNA insert in pUR289 was determined by agarose gel electrophoresis to be approximately 1.8 kb. Restriction map of the DNA insert from this recombinant plasmid indicated that it contained at least one restriction site for each of BamHI, HindIII and PstI. Subcloning experiments indicated that HindIII-HinIII fragment of the insert DNA was essential for gene expression while EcoRI-BamHI and EcoRi-PstI fragments were not. The smallest size of the insert capable for gene expression was about 1.4 kb. Southern blot analysis revealed one perfect hybridized band between PstI-XbaI fragment of the insert and BamHI digested chromosomal DNA from Streptomyces sp.190-1