The pK of Specific Groups of Proteins

Hill, Robert J.; Davis, Rosemary W.

doi:10.1016/s0021-9258(18)96009-6

Cited by 63 publications

(3 citation statements)

References 12 publications

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“…This apparently clear-cut situation prompted us to search for the extent of alkylation of the al valines and 8146 histidines in samples of hemoglobin alkylated either in the liganded or in the deoxy form. Investigations of Perutz et al (1980), Ohe & Kajita (1980), Gurd (Garner et al, 1963;Morrow et al, 1976;Matthew et al, 1977), and Hill & Davis (1967) indicated that these amino acid residues are Bohr effect groups.…”

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Anion Bohr effect of human hemoglobin

Bucci¹,

Fronticelli²

1985

Biochemistry

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The pH dependence of oxygen affinity of hemoglobin (Bohr effect) is due to ligand-linked pK shifts of ionizable groups. Attempt to identify these groups has produced controversial data and interpretations. In a further attempt to clarify the situation, we noticed that hemoglobin alkylated in its liganded form lost the Bohr effect while hemoglobin alkylated in its unliganded form showed the presence of a practically unmodified Bohr effect. In spite of this difference, analyses of the extent of alkylation of the two compounds failed to identify the presence of specific preferential alkylations. In particular, the alpha 1 valines and beta 146 histidines appeared to be alkylated to the same extent in the two proteins. Focusing our attention on the effect of the anions on the functional properties of hemoglobin, we measured the Bohr effect of untreated hemoglobin in buffers made with HEPES [N-(2-hydroxyethyl)piperazine-N'-2-ethanesulfonic acid], MES [2-(N-morpholino)ethanesulfonic acid], and MOPS [3-(N-morpholino)propanesulfonic acid], which being zwitterions do not need addition of chlorides or other anions for reaching the desired pH. The shape acquired by the Bohr effect curves, either as pH dependence of oxygen affinity or as pH dependence of protons exchanged with the solution, was irreconcilable with that of the Bohr effect curves in usual buffers. This indicated the relevance of solvent components in determining the functional properties of hemoglobin. A new thermodynamic model is proposed for the Bohr effect that includes the interaction of hemoglobin with solvent components. The classic proton Bohr effect is a special case of the new theory.

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Anion Bohr effect of human hemoglobin

Bucci¹,

Fronticelli²

1985

Biochemistry

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“…Since the solution was kept saturated with PhSCN, the reaction followed firstorder kinetics. The resulting first-order kinetic constants were treated according to the method of Hill and Davis (1967) as shown in Figure 1. From the slope of the resulting line the pXa of the amino group was calculated as 7.83, in good agreement with the value of 7.85 determined by direct titration at 40°.…”

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confidence: 99%

“…If the pifa value for the glycine amine were 8.2, then it would have the same pH independent rate constant as the phenylalanine amine with a p of 7.45. A study of the rate of reaction of these two groups as a function of pH in a fashion similar to that performed on Ala-Val in this work or on the a chain of hemoglobin by Hill and Davis (1967) might resolve this question but has not yet been attempted. (2) An alternate explanation for the anomalous reaction rate of GlyA1 is that the a-amine is inaccessible to the reagent, either because of tertiary structure within the monomer unit or because of aggregation of monomers (quaternary structure).…”

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confidence: 99%