PLASMID AND ESCHERICHIA-COLI TRANSFORMED THEREWITH

PURPOSE:To produce a thermostable alanine dehydrogenase, by linking a thermostable dehydrogenase gene having a specific mol. wt. or below to a vector plasmid, introducing the resultant recombinant plasmid into Escherichia coli and cultivating the obtained transformant strain in a culture medium. CONSTITUTION:A chromosomic DNA of Bacillus.sterothermophilus IFO12550 strain is digested with a restriction enzyme SalI to provide a DNA fragment, which is then linked to a plasmid pBR322 treated with the SalI with a T4 ligase to afford a plasmid pICR3. An exogenote region of the above-mentioned plasmid is subsequently taken out and introduced into an M13 phage vector to determine a DNA base sequence. A DNA fragment, capable of coding an alanine dehydrogenase and having