Plasmid incorporating polynucleotide phosphorylase gene - and a DNA fragment of a bacterial plasmid, and bacterial strains contg. the plasmid used to prepare phosphorylase polynucleotide

摘要

Novel plasmid comprises at least (a) a bacterial DNA fragment carrying a structural gene of polynucleotide phosphonylase and (b) a DNA fragment of a bacterial plasmid pref. from pBr322. Pref. (a) is of mol.wt. about 1.5 Md. Pref. plasmids are pBP280 and pBP111. The plasmids are prepd. by integrating, in a bacterial plasmid, a DNA fragment carrying a pnp (polynucleotide phosphonylase) gene and a neighbouring gene conferring a particular phoenotype pref. ArgG(+) (structural gene or arginine succinate synthetase). Bacterial strains transformed by the plasmid, esp. E.coli, are claimed. The plasmids are used to prepare polynucleotide phosphonylase by fermenting a culture medium of the above transformed bacterial strains and recovering the prod. The prod. is an exonuclease used for sequential degradation of ribopolymers or for polymerising ribonucleoside-5' disphosphates.