title: Overproduction of gene products by the super-high-copy-number plasmid pNR333.
abstract: The plasmid pNR333 is a kanamycin-resistant, deletion derivative of pNR113 with an extremely high copy number in Escherichia coli and in Proteus mirabilis. In order to determine the usefulness of pNR333 as a replication gene of vector, the genes encoding chloramphenicol acetyl-transferase (CAT) and beta-galactosidase (beta-gal) were cloned individually into both pNR333 and other low-copy-number plasmids. The expression of the cloned genes was compared by measuring the specific activity of each enzyme and the amounts of the proteins produced. A hybrid plasmid pNR333-cat expressed 53 times as much activity of CAT as the low-copy plasmid S-a which had a copy number of four. The lacZ gene cloned in pNR333 produced 17 times as much beta-gal as in the low-copy-number plasmid pNR1150. These results suggest that pNR333 is a useful vector plasmid for producing a large amount of polypeptides in E. coli hosts.
mesh_terms: D000123:Acetyltransferases / Q000096:biosynthesis / Q000235:genetics; D015500:Chloramphenicol O-Acetyltransferase; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D005786:Gene Expression Regulation; D005798:Genes, Bacterial; D005822:Genetic Vectors; D010957:Plasmids; D001616:beta-Galactosidase / Q000096:biosynthesis / Q000235:genetics
chemical_list: D000123:Acetyltransferases; D015500:Chloramphenicol O-Acetyltransferase; D001616:beta-Galactosidase