Thermal Stability and Cross-Linking of HB New York [β113(G15)VAL→GLU]

Abstract

Hb New York [β113(G15)Val→Glu] has been cross-linked with bis (3, 5-dibromosalicyl) fumarate, a reagent known to cross-link Lys 82β₁ and Lys 82β₂. 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°C for Hb New York, 42.2°C for Hb A, 53.7°C for cross-linked Hb New York, and 56.2°C for cross-linked Hb A. Transitions observed at 280 nm were approximately 2°C higher. Thus, a single inter-subunit cross-link can stabilize an abnormal hemoglobin. A model of Hb New York in which Glu β113 forms a salt bridge to His β117 can explain the small changes in both the stability and the electrophoretic mobility of this protein.