Figure 5
Role of translation in mRNA stability. Beta-galactosidase expression of M. smegmatis mc2155 transformed with the different plasmids, derived from pMYS694 (in the legend to Fig. 4A), by inserting M. smegmatis katG DNA regions of different length, downstream of the sigA promoter. All the plasmids carry the same region from 437 to the start codon of katG (coordinate 499, see Fig. 1), and differ for the length of the following open reading frame: pMYS690 and pMYS727 carry the same DNA region, but the katG translation start codon TTG has been substituted in pMYS727 with a CCG codon; pMYS720 is mutated in the start codon of katG (TTG to TAA codon); pMYS723 and pMYS744 carry 11 and 19 codons of katG, respectively. Strain mc2155 was transformed with the plasmids and beta-galactosidase expression was measured, as described in Methods. Average beta-galactosidase activity in Miller Units of three to eight different replicas ± standard deviation is reported. The average relative increment in beta-galactosidase activity is also indicated. The amount of lacZ transcript was evaluated by quantitative RT-PCR. N.T. = not tested.