Hb - a of the N-terminal amino group of the alpha-chains....

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Oxy Hb The central cavity between the four subunits is shown in black. This cavity is filled with water. Image is from the x-ray coordinates from the Protein Data Bank at the NIH, viewed with the program Chime .
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1-subunit (yellow) and 1-subunit (red) of Hb. Note how the two globular proteins interdigitate at numerous points. Image is from the x-ray coordinates from the Protein Data Bank at the NIH, viewed with the program Chime .
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Salt bridges in deoxyhemoglobin. In class we have repeatedly mentioned that there are about 13 salt bridges (+/- bonds) in deoxy Hb. The diagram below indicates where 8 of those are (see dashed lines below). Notice that the majority of them are between subunits. Also drawn is where the allosteric effector, chloride ion, binds. Cl increases the pK
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Unformatted text preview: a of the N-terminal amino group of the alpha-chains. These two N-termini together account for about 30% of the H + portion of the Bohr effect. The majority (approximately 40%) of the H + Bohr effect occurs at the C terminal histidine (his146) of the beta-chains. The other 30% of the H + Bohr effect occurs at several other residues on hemoglobin. Cl creates additional salt bridges, favoring the T form of hemoglobin. Chloride would be considered a negative heterotropic allosteric effector. 2 Asp His + NH 3 + C O O F G 1 H C 3 Arg + Asp 1 Lys + COO N H 3 + HC3 H9 C5 Cl Cl L y s + 2 Asp Arg + NH 3 + C O O C 5 H 9 H C 3 His + Asp 1 COO N H 3 + HC3 FG1 Nelson and Cox, Lehninger Principles of Biochemistry...
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Hb - a of the N-terminal amino group of the alpha-chains....

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