Primer extension assays. Primer extension assays were performed for znuC, znuA and ykgM, by using RNA isolated from the exponential-phase of both WT and Δzur grown in TMH medium with 5 mM of Zn2+. An oligonucleotide primer complementary to the RNA transcript of each gene was designed from a suitable position. The primer extension products were analyzed with 6% acrylamide sequencing gel. Lanes C, T, A and G represented the Sanger sequencing reactions. On the right side, DNA sequences were shown from the bottom (5') to the top (3'), and the transcription start sites were underlined.