Carbon monoxide complex of cytochrome b(5) at acidic pH

CO complex of cyt b(5) generated at acidic pH is investigated by absorption , resonance Raman (RR), and far UV CD measurements. The Soret maximum wavel ength blue-shifted to 420 nm with other absorption bands observed around 54 0 and 570 nm for reduced cyt b(5) upon interaction with CO at acidic pH (pH 3.1-3.5), Under this condition, the iron-carbon stretching RR band was obs erved at 529 cm(-1) (520 cm(-1) for (CO)-O-18), which indicated formation o f a heme-CO adduct with a histidine as an axial ligand. Heme dissociated fr om the reduced cyt b(5) protein at pH similar to3.5, whereas its rate decre ased under CO atmosphere compared with N-2 atmosphere, due to formation of a heme-CO adduct with a histidine as an axial ligand. (C) 2001 Academic Pre ss.