Table 1. ArgR-regulated ornithine transcarbamylase expression in chemostat grown cultures.

	Feed arginine, mM
Allele	0	1
argRB	1.00 ± 0.02	2.06 ± 0.03
argRK12	1.42 ± 0.14	0.14 ± 0.02
argR38	67.35 ± 0.68	68.71 ± 0.68

Activities per mg of cell protein were determined by standard methods (4-6) and normalized to ArgR^B activities at 0 mM arginine.