Transport of Pyrimidine Nucleosides in Cells of Escherichia coli K 12

Abstract

1 The transport of pyrimidine nucleosides into cells of Escherichia coli has been investigated in mutant strains which cannot metabolize these nucleosides. Such cells transport and concentrate pyrimidine nucleosides several hundred-fold. 2 The transport is inhibited by energy poisons and by sulfhydryl reagents. 3 Pyrimidine nucleosides compete mutually for transport. Adenosine is also a strong competitor while guanosine and inosine are weak competitors. 4 The rate of pyrimidine nucleoside transport is shown to be under control of the cytR and deoR gene products, which are also known to regulate the synthesis of nucleoside-catabolizing enzymes. The transport system is repressed by growth on glucose, as is the synthesis of the enzymes.