title: Cloning and expression of the yeast galactokinase gene in an Escherichia coli plasmid.
abstract: This report describes the construction and isolation of a plasmid, derived from pBR322, which carries a BglII restriction fragment of DNA containing the galactokinase gene from Saccharomyces cerevisiae. This was accomplished by the following procedure: (1) Purified galactokinase mRNA, labelled with 125I, was hybridized to BglII digests of yeast DNA employing Southern's filter transfer technique to identify a restriction fragment containing the galactokinase gene. (2) This fragment was partially purified by agarose gel electrophoresis, ligated into the BamHI site of pBR322 and transformed into Escherichia coli to generate a clone bank containing the galactokinase gene. (3) This bank was screened by in situ colony hybridization with galactokinase mRNA resulting in the identification of a plasmid carrying this gene. This plasmid DNA hybridized with the galactokinase mRNA to the same extent in the presence of absence of a large excess of unlabelled mRNA from cells that were not induced for galactokinase synthesis, while the same amount of unlabelled galactose-induced mRNA reduced the hybridization by 95%. When this plasmid was introduced into an E. coli strain deleted for the galactose operon it caused the synthesis of low levels of yeast galactokinase activity.
mesh_terms: D004274:DNA, Recombinant / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology*; D005686:Galactokinase / Q000096:biosynthesis / Q000235:genetics*; D005796:Genes; D009693:Nucleic Acid Hybridization; D010957:Plasmids; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D014158:Transcription, Genetic
chemical_list: D004274:DNA, Recombinant; D012333:RNA, Messenger; D005686:Galactokinase