Crystal structure of carbonmonoxy sickle hemoglobin in R-state conformation.

ABSTRACT: The fundamental pathophysiology of sickle cell disease is predicated by the polymerization of deoxygenated (T-state) sickle hemoglobin (Hb S) into fibers that distort red blood cells into the characteristic sickle shape. The crystal structure of deoxygenated Hb S (DeoxyHb S) and other studies suggest that the polymer is initiated by a primary interaction between the mutation ?Val6 from one Hb S molecule, and a hydrophobic acceptor pocket formed by the residues ?Ala70, ?Phe85 and ?Leu88 of an adjacent located Hb S molecule. On the contrary, oxygenated or liganded Hb S does not polymerize or incorporate in the polymer. In this paper we present the crystal structure of carbonmonoxy-ligated sickle Hb (COHb S) in the quaternary classical R-state at 1.76Å. The overall structure and the pathological donor and acceptor environments of COHb S are similar to those of the isomorphous CO-ligated R-state normal Hb (COHb A), but differ significantly from DeoxyHb S as expected. More importantly, the packing of COHb S molecules does not show the typical pathological interaction between ?Val6 and the ?Ala70, ?Phe85 and ?Leu88 hydrophobic acceptor pocket observed in DeoxyHb S crystal. The structural analysis of COHb S, COHb A and DeoxyHb S provides atomic level insight into why liganded hemoglobin does not form a polymer.

SUBMITTER: Ghatge MS 

PROVIDER: S-EPMC4859812 | biostudies-literature | 2016 Jun

REPOSITORIES: biostudies-literature