IHIC Variants List

Hemoglobin Nouakchott [alpha 114(GH2)Pro----Leu]: a new hemoglobin variant displaying an unusual increase in hydrophobicity

The most striking fact in Hb Nouakchott [alpha 114(GH2)Pro----Leu] is the highly increased hydrophobicity of the abnormal chain. In comparison to other variants carrying the same amino-acid substitution, but at another position, the involvement of the environmental domains in the expression of the hydrophobicity is shown. Even though the substitution concerned a proline residue, it was without consequences on the oxygen binding and the stability of the molecule.

Structure-function of Hb Marseille-Long Island [alpha 2 beta 2 N-methionyl-2(NA2) His----Pro]

Suspensions of red cells containing Hb Marseille-Long Island showed decreased oxygen affinity and low interaction with 2,3-diphosphoglycerate. Oxygen equilibrium studies of the purified component confirmed these abnormalities. Oxidation rate measurements of carbonmonoxy-Hb Marseille and carbonmonoxy-Hb A by ferricyanide showed an increased rate for the former, suggesting an increased dissociation constant for carbon monoxide. Nuclear Magnetic Resonance spectra in the high field region revealed small changes in the proximal region of the heme pocket. These results indicated that the mutation causes a perturbation at a distance from the mutation site.

Thermal stability and cross-linking of Hb New York [beta 113(G15)Val----Glu]

Hb New York [beta 113(G15)Val----Glu] has been cross-linked with bis (3,5-dibromosalicyl) fumarate, a reagent known to cross-link Lys 82 beta 1 and Lys 82 beta 2. Thermal denaturations of met Hb New York and its derivative have been compared to those of the corresponding Hb A samples. The structural transitions, observed as absorbance changes at 418 nm, were at 40.2 degrees C for Hb New York, 42.2 degrees C for Hb A, 53.7 degrees C for cross-linked Hb New York, and 56.2 degrees C for cross-linked Hb A. Transitions observed at 280 nm were approximately 2 degrees C higher. Thus, a single inter-subunit cross-link can stabilize an abnormal hemoglobin. A model of Hb New York in which Glu beta 113 forms a salt bridge to His beta 117 can explain the small changes in both the stability and the electrophoretic mobility of this protein.