The effects of the left-shifting, anti-sickling compound BWl2C (5-(2-formyl-3-hydroxyphenoxy)pentanoic acid) on the oxygen saturation curve of whole chicken blood and the isolated major (AII) and minor (AI) components of chicken hemoglobin have been studied. The results support the postulated major binding mode for BWl2C to human hemoglobin of bridging between the a-chain terminal amino groups in the oxy conformation with an important hydrophobic component contributed mainly by Pro 77a residues. In chicken AI1 (Pro 77a+Ser) BWI2C still left-shifts at high concentrations but its potency is greatly reduced (at least lo-fold). In chicken AI (Pro 77a+Ser and Val la+Met) BWl2C is a right-shifter with a potency comparable to that of 2,3-diphosphoglycerate suggesting that binding at the /I-chain termini in the deoxy conformation is now dominant with a-chain binding no longer significant.
B W12COxygen saturation curve (Chicken blood) Left-shift Hemoglobin Anti-sickling