FIG. 4.

(A) A schematic representation of mutant HemRs and their phenotypes after expression in the E. coli heme biosynthesis mutant. The testing for growth stimulation was done on LB and NBD plates essentially as described in the legend to Fig. 1. Growth stimulation with four different (DIF.) heme sources, myoglobin (MY), hemoglobin (HB), heme (HM), and HSA (HSA-heme complex, is indicated as follows: +, stimulation of growth; −, no stimulation; ∗ and −/+, very light or small zone of stimulation. HemR^W.T., wild-type HemR. (B) Growth zones of HemR histidine mutants around discs soaked in 10 μl of 10 mM heme (NBD plates). WT, wild type.