FIG 5.

Y57A Cj1386 can be reconstituted with hemin and displays 1:1 hemin-binding stoichiometry. (A) Absorption spectra of Cj1386^Y57A when titrated with hemin at 1 μM increments against 10 μM apo-Cj1386^Y57A in 100 mM NaCl, 20 mM Tris, pH 7.4. Arrows represent the direction of increased absorbance readings upon hemin addition. (B and C) Differential absorption spectra of Cj1386^Y57A at Soret peaks at 372 nm and 412 nm. The dashed line represents the concentration of Cj1386^Y57A and hemin that yield a 1:1 heme-to-Cj1386^Y57A binding ratio. Error bars represent the standard errors as determined from hemin titration from 2 independent protein purifications.