Useful modifications of the Escherichia coli expression plasmid pJL6

Several useful modifications of the Escherichia coli expression plasmid pJL6 have been constructed. These include the introduction of a wide variety of restriction sites by the cloning of oligonucleotide linker DNA or of a short DNA fragment containing many sites. These plasmids can allow the expression of genes adjacent to one of the restriction sites provided. Another plasmid, pJLA16, allows the cloning of blunt-ended DNA adjacent to the fragment of phage gene, thus allowing fusions of this gene fragment with target gene DNA. This facilitates the expression of genes on blunt-ended DNA fragments that are either directly the product of restriction enzyme digestion or fragments that are resected with Bal-31 nuclease.