Construction of beta-lactamase-encoding ApR gene cassettes for rapid identification of cloned genes

We have constructed two Escherichia coli plasmids, pYK18 and pYK19, from which the BamHI, SmaI or EcoRI DNA fragments containing the ApR gene, conferring resistance to ampicillin, can be excised. The ApR cassettes have an annealing site for the sequencing primer of pUC plasmids at each end. Therefore, when the cassette is inserted into a gene, we can determine the nucleotide sequence of the gene from the insertion site using the sequencing primers of the pUC plasmids. This method is useful for identifying a cloned gene.