Human Carboxyhemoglobin at 2.2 Å Resolution: Structure and Solvent Comparisons of R-State, R2-State and T-State Hemoglobins

Abstract

Abstract1.

The Allosteric Properties of Hemoglobin: Insights from Natural and Site Directed Mutants

“…the distal His and the residue downstream one turn of the helix) impinge over the heme, too far away to make direct contact with it, but close enough to interact with the bound ligand. In Mb and the α chains of Hb (but not in the β) His E7 establishes a H-bond with bound oxygen [72,18], that has a bond angle of 120° to 160° in hemoproteins and in heme model compounds [73,18] and forces CO to a similar bent position [19,74,75], in spite of the fact that in heme model compounds CO adopts a linear geometry, normal to the porphyrin plane. Moreover His E7 increases the polarity of the heme pocket, again favouring O 2 over CO. Because of these reasons, His E7 is thought to be crucial to ligand discrimination, and it has been suggested that in its absence poisoning from endogenously produced CO would have lethal consequences.…”

Mechanisms of Homogeneous Nucleation of Polymers of Sickle Cell Anemia Hemoglobin in Deoxy State

“…However, dynamic light-scattering characterization of Hb solutions prepared following procedures identical with those used here showed a single species of a size between 5 nm and 6 nm, 66 compatible with the 5.5 nm known for hemoglobin. 67,68 The high limit of the detection range of these determinations is above 1 mm. In view of the high sensitivity of light-scattering to larger species (e.g.…”

1.25 Å Resolution Crystal Structures of Human Haemoglobin in the Oxy, Deoxy and Carbonmonoxy Forms

“…19 A similar angle was found in COHb refined to 2.2 ) using human Hb, which transpired to be a mutant at the surface. 20 Spectroscopic studies have not supported the idea of a bent geometry, and strongly suggest the ligand pushes the distal residues aside to adopt its preferred conformation. One difficulty with the crystallographic refinements is that the ligand oxygen atom is largely unconstrained by its one chemical bond, and in the absence of very high resolution data the model must be restrained carefully using prior information.…”