Hbs tetramerHemoglobin crystals

Sickle-Cell Hemoglobin (HbS)

    Hemoglobin is a tetrameric protein with two alpha and two beta subunit chains. The standard form is HbA. In the HbS form, replacement of glu by val in the two beta subunits (dark grey) where they contact the alpha subunits [top, left]. Under conditions of reduced oxygen tension in the blood, the modified tetramer undergoes a conformational shift that forms stable crystals [top, right]. Crystal formation result in sickle-shaped red blood cells [below, left].

All text material © 2014 by Steven M. Carr