Clues for discovering a new biological function of Vitreoscilla hemoglobin in organisms: potential sulfide receptor and storage.

The interaction between H2 S and Vitreoscilla hemoglobin (VHb) has been studied by UV-Vis and Resonance Raman spectroscopes to confirm the binding between the ligand and the protein. Kinetic constants, kon = 1.2 × 10(5) m(-1) ·s(-1) and koff = 2.5 × 10(-4) ·s(-1) , have been determined and compared with those for mammalian hemoglobins. Density Functional Theory study supports the binding of H2 S by modeling the configurations of HOMO dispersions. We hypothesized that VHb is involved in H2 S reception and storage. Different from Lucina pectinata HbI, a typical H2 S-binding hemoglobin, VHb, exhibits unusual properties on H2 S reactivity such as steric constraints playing an important role in modulating H2 S entry. A distinct mechanism of VHb interaction with H2 S is supported by studies of variant forms of VHb.