1hbb: Difference between revisions

==Overview==

The mutation site in hemoglobin Rothschild (37 beta Trp----Arg) is located, in the "hinge region" of the alpha 1 beta 2 interface, a region that is, critical for normal hemoglobin function. The mutation results in greatly, reduced cooperativity and an oxygen affinity similar to that of hemoglobin, A [Gacon, G., Belkhodja, O., Wajcman, H., & Labie, D. (1977) FEBS Lett., 82, 243-246]. Crystal were grown under "low-salt" conditions [100 mM Cl-, in 10 mM phosphate buffer at pH 7.0 with poly(ethylene glycol) as a, precipitating agent]. The crystal structure of deoxyhemoglobin Rothschild, and the isomorphous crystal structure of deoxyhemoglobin A were refined at, resolutions of 2.0 and 1.9 A, respectively. The mutation-induced, structural changes were partitioned into components of (1) tetramer, rotation, (2) quaternary structure rearrangement, and (3) deformations of, tertiary structure. The quaternary change involves a 1 degree rotation of, the alpha subunit about the "switch region" of the alpha 1 beta 2, interface. The tertiary changes are confined to residues at the alpha 1, beta 2 interface, with the largest shifts (approximately 0.4 A) located, across the interface from the mutation site at the alpha subunit FG, corner-G helix boundary. Most surprising was the identification of a, mutation-generated anion-binding site in the alpha 1 beta 2 interface., Chloride binds at this site as a counterion for Arg 37 beta. The, requirement of a counterion implies that the solution properties of, hemoglobin Rothschild, in particular the dimer-tetramer equilibrium, should be very dependent upon the concentration and type of anions, present.

==About this Structure==

[[Category: oxygen transport]]