A cDNA, PHCC-TPx, specifying a protein highly homologous to known phospholipid hydroperoxide glutathione peroxidases was isolated from a Chinese cabbage cDNA library.
In Escherichia coli, the arginine repressor, the product of the argR gene, in coijunction with L-arginine controls the synthesis of the enzymes of arge biosynthesis. We describe the nucleotide sequence ofthe argR gene, including its control region, and show that formation of the repressor is autoregulated. The argR control region contains two promoters, one of which overlaps the operator site and, as with other ar genes, consists of two adjacent palindromic sequences ("ARG boxes"). The arginine repressor protein and an arginine repressor-l-galactosidase fusion protein were purified, and the amino acid sequence of the N-terminal end of the repressor protein portion of the fusion protein was determined. Antibodies prepared against the fusion protein react with the repressor. The repressor is precipitable by L-arginine, which facilitates its purification. The native repressor is a hexamer with a molecular weight of 98,000; its monomeric subunit has a molecular weight of 16,500. To verify its properties postulated from genetic studies, we show that in the presence of L-argmine, repressor inhibits transcription of argF and binds to the ARG boxes of arBF and argR.
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