Conformation and cooperativity in hemoglobin

Huestis, Wray H.; Raftery, Michael A.

doi:10.1021/bi00680a013

Cited by 42 publications

(11 citation statements)

References 28 publications

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“…The results of nmr experiments on n-butyl isocyanide binding conducted in this laboratory (Huestis and Raftery, 1972c) were consistent with the conclusions drawn from the carbon monoxide binding experiments.…”

Section: H U E S T I S a N D R A F T E R Ysupporting

confidence: 86%

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Characterization of intermediate states in the ligation of hemoglobin

Huestis¹,

Raftery²

1973

Biochemistry

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Section: H U E S T I S a N D R A F T E R Ysupporting

confidence: 86%

“…Human hemoglobin was isolated, purified, and trifluoroacetonylated as previously described (Huestis and Raftery, 1972a).…”

Section: Methodsmentioning

confidence: 99%

Characterization of intermediate states in the ligation of hemoglobin

Huestis¹,

Raftery²

1973

Biochemistry

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“…A plot of the oxygen saturation of the ß chains vs. the total oxygen saturation using the present model is shown in Figure 2. As can be seen from this plot for case E in Table I, the lag of the ß chain ligation is not as dramatic as might initially be supposed from the assumption of extreme heterogeneity in the T state and is of the magnitude found experimentally through fluorine NMR measurements (Huestis & Raftery, 1975). However, the fluorine NMR results may be inconsistent with a more recent proton NMR study (Viggiano & Ho, 1979).…”

Section: Discussionmentioning

confidence: 56%

Allosteric interpretation of the oxygen-binding reaction of human hemoglobin tetramers

Robert²,

Gill³

1987

Biochemistry

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An allosteric model is presented that provides a simple explanation for the low population of triply ligated species, relative to the other species, in the oxygenation of human hemoglobin tetramers as found in high-concentration studies [Gill, S. J., Di Cera, E., Doyle, M. L., Bishop, G. A., & Robert, C. H. (1987) Biochemistry (preceding paper in this issue)]. The model is a quantitative interpretation of the Perutz mechanism [Perutz, M. F. (1970) Nature (London) 228, 726-739] and is based on a number of structural and thermodynamic findings so far reported in the analysis of hemoglobin properties. Human hemoglobin is assumed to exist in two quaternary states: the T or low-affinity state and the R or high-affinity state. An extreme chain heterogeneity in the T state is postulated so that oxygen binds only to the alpha chains. Nearest-neighbor interactions between the alpha chains may lead to cooperativity within the T state. The R state is noncooperative, and both the alpha and beta chains have equal oxygen affinity.

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“…There are well-known structural and functional differences in the protein environments of the heme group in the α- and β-subunits of deoxyhemoglobin, 54a,d, for example, resulting in the heme groups of the α-chains having higher oxygen affinity than those of the β-chains . Therefore, it was of interest to see whether the new method could uncover any unreported differences in the heme structures of the subunits.…”

Section: Resultsmentioning

confidence: 99%

Structural Characterization of Synthetic and Protein-Bound Porphyrins in Terms of the Lowest-Frequency Normal Coordinates of the Macrocycle

1997

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The X-ray crystal structures of synthetic and protein-bound metalloporphyrins are analyzed using a new normal structural decomposition method for classifying and quantifying their out-of-plane and in-plane distortions. These distortions are characterized in terms of equivalent displacements along the normal coordinates of the D 4h -symmetric porphyrin macrocycle (normal deformations) by using a computational procedure developed for this purpose. Often it turns out that the macrocyclic structure is, even in highly distorted porphyrins, accurately represented by displacements along only the lowest-frequency normal coordinates. Accordingly, the macrocyclic structure obtained from just the out-of-plane normal deformations of the saddling (sad, B 2u )-, ruffling (ruf, B 1u )-, doming (dom, A 2u )-, waving [waV(x), waV(y); E g ]-, and propellering (pro, A 1u )-type essentially simulates the out-of-plane distortion of the X-ray crystal structure. Similarly, the observed inplane distortions are decomposed into in-plane normal deformations corresponding to the lowest-frequency vibrational modes including macrocycle stretching in the direction of the meso-carbon atoms (meso-str, B 2g ), stretching in the direction of the nitrogen atoms (N-str, B 1g ), x and y pyrrole translations [trn(x), trn(y); E u ], macrocycle breathing (bre, A 1g ), and pyrrole rotation (rot, A 2g ). The finding that the displacements of the 24 atoms of the macrocycle primarily occur along the lowest-frequency normal coordinates is expected on physical grounds and is verified by structural decomposition of more than 100 synthetic and 150 protein-bound metalloporphyrin X-ray crystal structures. Because of the high resolution of the X-ray crystal structures of synthetic metalloporphyrins, the small displacements for other normal coordinates are also able to be discerned. However, for the heme groups in proteins, only the displacements along the lowest-frequency modes are detectable because of the large uncertainties in the atomic positions. The heme groups in the four X-ray crystal structures of deoxyhemoglobin are used to evaluate the structural decomposition method. We find that the corresponding heme groups in different X-ray crystal structures are similar. Furthermore, the outof-plane distortions for the heme groups in the R-and -chains are found to be inequivalent, that is, the two

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Conformation and cooperativity in hemoglobin

Cited by 42 publications

References 28 publications

Characterization of intermediate states in the ligation of hemoglobin

Characterization of intermediate states in the ligation of hemoglobin

Allosteric interpretation of the oxygen-binding reaction of human hemoglobin tetramers

Structural Characterization of Synthetic and Protein-Bound Porphyrins in Terms of the Lowest-Frequency Normal Coordinates of the Macrocycle

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