FIG. 1.

Comparison of the abilities of heme and Hb receptors, HemR and HmbR, to use different heme-protein complexes as sources of iron and porphyrin in the E. coli heme biosynthesis mutant IR1532. HemR and HmbR receptors were expressed from low-copy-number plasmids pWKS130 and pWKS30, respectively (49). The expression of HmbR was done in the presence of N. meningitidis tonB exbB exbD genes (47). Bars represent the surface areas of bacterial growth around the discs on NBD plates (error bars show the standard deviations). Discs were soaked with equimolar amounts of heme-containing compounds (except for heme, see Material and Methods). Each measurement was repeated at least three times. Abbreviations: HB, hemoglobin; HPX, human hemopexin; HPT-HB, human haptoglobin-Hb complex; MY-M, skeletal muscle myoglobin; MY-H, heart muscle myoglobin.