Inefficient heme transfer from Shr to apoHtsA. ApoHtsA or apoShp (75 μM) was incubated with 15 μM Shr in 0.1 ml of 20 mM Tris-HCl, pH 8.0, at room temperature for 2 min. Each sample was then loaded onto a 0.1-ml SP Sepharose column and eluted as described in the text. Presented are the normalized spectra of Shr without or with treatment with apoHtsA or apoShp. The normalization was done by setting A280 = 1.0.