Hemoglobin hydrophobic pocket

Figure 3.14 Sickle-cell hemoglobin molecules polymerize due to the hydrophobic patch introduced by the mutation Glu 6 to Val in the P chain. The diagram (a) illustrates how this hydrophobic patch (green interacts with a hydrophobic pocket (red) in a second hemoglobin molecule, whose hydrophobic patch interacts with the pocket in a third molecule, and so on. Electron micrographs of sickle-cell hemoglobin fibers are shown in cross-section in (b) and along the fibers in (c). [(b) and (c) from J.T. Finch et al., Proc. Natl. Acad. Set. USA 70 718-722, 1973.)...

All successful myoglobin and hemoglobin model compounds provide steric bulk on the distal side of the porphyrin ring with a hydrophobic pocket for complexation of dioxygen as well as a bulky alkyl imidazole proximal ligand... 

The heme pocket. The helices of hemoglobin (and myoglobin) form a hydrophobic pocket for the heme and provide an environment where the iron atom reversibly binds oxygen. The chemical structure of heme is shown in figure 5.10 and is described in atomic detail in chapters 10 and 14. (Illustration copyright by Irving Geis. Reprinted by permission.)... 

Structure of hemoglobin S (HbS) polymer. The valine at the j66 position of the deoxy-HbS fits into the hydrophobic pocket formed by leucine and phenylalanine at jS85 and j688 of an adjacent chain. Since each chain has an acceptor pocket and a donor valine, the HbS polymer has a double-stranded, half-staggered structure. [Reproduced with permission from S. Charache, Advances in the understanding of sickle cell anemia. Hasp. Pract. 21(2), 173 (1986). J. E. Zupko, illustrator.]... 

Globin The globular proteins that are the polypeptide components of myoglobin and hemoglobin. They contain a hydrophobic pocket that holds the heme prosthetic group. 

Heme in hemoglobin/myoglobin relatively deep inside a hydrophobic pocket. At Fe(II) one axial position is more strongly and the other axial position more weakly coordinated by a Lewis base of an amino acid residue. The weak axially coordinated side is free for reversible binding of O2 (see Section 2.3.1). 

Hemoglobins share a common molecular architecture, composed of a polypeptide backbone and an iron porphyrin, as illustrated in Fig. 1. Molecular oxygen binds to the Fe at the center of the planar heme b (Fe protoporphyrin IX). The polypeptide adopts the globin fold constructed primarily from a-helices, customarily labeled with the letters A-H. The heme group binds tightly to a hydrophobic pocket formed primarily from the E- and F-helices. and a bond between the heme Fe and the e-nitrogen of a histidine in the F-helix (His F8) provides the only covalent link between the polypeptide and the heme. 

Imately 65 X 55 X 50 It Is composed of four polypeptide chains each resembling quite closely the myoglobin chain The three dimensional structure of the subunits Is held together by weak noncovalent bonds The polar amino acid side chains are In contact with the solvent, and the nonpolar residues are located In the Interior of the molecule or In regions which form the contacts between chains The heme group Is located In a pocket In each chain residues In contact with heme are Invariable ( e are the same In different mammalian hemoglobins) and the bonds between heme and chain are hydrophobic Interactions Contacts between like chains (a-a are... 

In hemoglobin and myoglobin the globin protein protects the ferroheme, which is tucked into a hydrophobic crevice of the protein, known as the heme pocket . 

Fig. 7.11. Myoglobin and hemoglobin. Myoglobin consists of a single polypeptide chain, which is similar in structure to the a and P subunits of hemoglobin. In all of the subunits, heme is tightly bound in a hydrophobic binding pocket. The proximal histidine extends down from a helix to bind to the Fe atom. The oxygen binds between the distal histidine and the heme. Panel C displays the quaternary structure of hemoglobin (From Frescht A. Structure and Mechanism in Protein Science. New York WH Freeman and Company, 1999. Used with permission.)...

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