CLONING AND NUCLEOTIDE-SEQUENCE OF THE GCV OPERON ENCODING THE ESCHERICHIA-COLI GLYCINE-CLEAVAGE SYSTEM

P-protein, H-protein and T-protein of the glycine cleavage system have been purified from Escherichia coli. Their N-terminal amino acid sequ ences were determined, and a set of oligonucleotide probes was designe d for gene cloning. The nucleotide sequence of a fragment of DNA aroun d the 62-min region of the E. coli chromosome, containing genes for th e components of the glycine-cleavage system has been determined. The s equence includes three structural genes encoding T-protein (363 amino acids, 40013 Da), H-protein (128 amino acids, 13 679 Da) and P-protein (956 amino acids, 104240 Da). These genes are named gcvT, gcvH and gc vP, respectively. They are organized in the above-mentioned order on t he same strand of DNA with short intercistronic sequences. The presenc e of a potential promoter preceding gcvT and a typical rho-independent terminator sequence following gcvP indicated that the three genes con stitute a single operon. Each component of the E. coli glycine-cleavag e system exhibits considerable amino acid sequence similarity with the animal and plant counterparts. When the plasmid containing the gcv op eron was transfected in E. coli cells, the gene products of gcvT, gcvH and gcvP were overexpressed under the direction of the promoter of th e gcv operon. However, bacteria harboring the plasmid that contained t he gcv operon without the promoter region and the 5' terminal portion of gcvT failed to overexpress any of the three components.