Studies of the interaction between heme oxygenase - 1 and human HBP

Abstract

The presented work aimed to examine for the first time the interaction between heme oxygenase -1 (HO-1) and heme bound human HBP (hHBP). The protein hHBP is thought to be a heme binding protein involved in heme transport during heme metabolism in cells, although the exact function is unknown. Heme binds with a mM Kd. Therefore if hHBP is being used to transport heme, a partner needs to be present to accept the heme ring. Unpublished results have shown that HO-1 is present when hHBP is knocked down in hepatic cell moodels, therefore HO-1 could be possible partner for hHBP. Both proteins were overexpressed in a bacterial host system. HO-1 was grown in non isotopically labeled media while hHBP was grown in M9 media with 15N, labeling. hHBP was purified using affinity chromatography while anion exchange chromatography was used for HO-1. To initially study the binding of heme to HO-1 UV-vis spectroscopy was used with the heme absorbance at 405nm being followed. Binding was observed as expected. Heme tritration with HO-1, hHBP and mixtures of hHBP/HO-1 were carried out to follow the fate of the heme molecule. NMR spectroscopy was also used to see if HO-1 could remove heme from heme-bound hHBP. The results indicate that HO-1 cannot in fact remove heme from hHBP.