Cloning and characterization of the glycine-cleavage enzyme system of Escherichia coli.

The glycine-cleavage enzyme system of Escherichia coli has been cloned in the cosmid vector pMF7. The recombinant plasmid, designated pGS64, carries two 19.4-kb EcoRI insert fragments. One of these fragments, which carries the gcv system, was subcloned from plasmid pGS64 into the plasmid vectors pACYC184 and pSC101 (creating plasmids pGS96 and pGS97, respectively). Plasmid pGS97, but not pGS96, complements a gcv mutant on glycine-supplemented plates. Enzyme assays, however, verified that both plasmids carry an inducible gcv system. The location of the gcv system in plasmid pGS97 was determined by Tn5 insertional inactivation. Subcloning experiments identified the region on the 19.4-kb fragment that inhibits growth in strains transformed with plasmid pGS96 and a region that is possibly involved in negative regulation of the gcv system.