Fig. 5. Derepression of SAM’s inhibitory effect by over-expression of tRNAfMet.
a The genetic organization of the met operon locus in the recombinant strain Xcc 8004-3F. A 3xFLAG-tag and a stop codon (TAA) were inserted between XC1251 and XC1252 to monitor the expression of XC1251. b Western blot detection of XC1251-3F in strain Xcc 8004-3F carrying different plasmids. The culture was grown in MMX alone (SAM−) or MMX supplemented with 2.5 µM SAM (SAM+). pBBad: an expression vector; p4335, p4339, and p4339M: the recombinant pBBad expressing tRNAMet1, tRNAfMet, and tRNAfMet mutant (73U74A → 73A74U) that lost the binding ability with SAM-IXcc, respectively. RNA polymerase β sub-unit (RpoB) protein was used as a control. c Plot of GUS activities produced by the reporter strain 8004/pWT-SD− carrying the series of plasmids in b in response to SAM. The culture was grown in MMX alone (SAM−) or MMX supplemented with 250 µM SAM (SAM+). Data are presented as mean values ± SD from three biologically independent samples. Different letters above the columns represent the significant difference at P < 0.05 by Student’s two-tailed t-test. Columns marked with the same letter are not significantly different from one another. Representatives of colorimetric samples for each condition were also included in the graph. Source data are provided as a Source Data file.