Table 2. Ratios of mRNA levels for methionine biosynthetic genes under different conditions of S or N availability.

	S or N source
	Glutathione	S downshift	S upshift	Arginine	N downshift	N upshift
Average met*	2.35	2.47	0.54	0.91	0.58	2.12
metE	0.27	0.23	1.06	0.59	0.17	3.54

Values were determined relative to those on sulfate or ammonium as the S or N source, respectively, or relative to those before shift. Growth conditions were as described (1). For S shifts, samples were taken 30 min after shift. For N shifts, samples were taken 10 and 30 min after shift, and values were averaged. Effects were larger 10 min after shift, particularly for upshifts.

^*Average values for metA, B, C, F, K, and L