[17] Circular dichroism spectra of hemoglobins

Geraci, Giuseppe; Parkhurst, Lawrence J.

doi:10.1016/0076-6879(81)76127-5

Cited by 53 publications

(41 citation statements)

References 36 publications

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“…4). Above 300 nm, the optical activity of the heme results from short and long distance interactions of the heme with the protein matrix, specifically attributed by theoretical calculations to a coupled oscillator interaction between the heme transitions and those of the surrounding aromatic side chains (53,54). This interpretation is consistent with the altered microenvironments of the aromatic amino acids of these ␤6 mutants, as indicated by the fluorescence and UVRR spectroscopic results.…”

Section: Discussionsupporting

confidence: 76%

Solution-active Structural Alterations in Liganded Hemoglobins C (β6 Glu → Lys) and S (β6 Glu → Val)

Hirsch¹,

Juszczak²,

Fataliev³

et al. 1999

Journal of Biological Chemistry

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Based upon existing crystallographic evidence, HbS, HbC, and HbA have essentially the same molecular structure. However, important areas of the molecule are not well defined crystallographically (e.g. the N-terminal nonhelical portion of the ␣ and ␤ chains), and conformational constraints differ in solution and in the crystalline state. Over the years, our laboratory and others have provided evidence of conformational changes in HbS and, more recently, in HbC.We now present data based upon allosteric perturbation monitored by front-face fluorescence, ultraviolet resonance Raman spectroscopy, circular dichroism, and oxygen equilibrium studies that confirm and significantly expand previous findings suggesting solution-active structural differences in liganded forms of HbS and HbC distal to the site of mutation and involving the 2,3-diphosphoglycerate binding pocket. The liganded forms of these hemoglobins are of significant interest because HbC crystallizes in the erythrocyte in the oxy form, and oxy HbS exhibits increased mechanical precipitability and a high propensity to oxidize. Specific findings are as follows: 1) differences in the intrinsic fluorescence indicate that the Trp microenvironments are more hydrophobic for HbS > HbC > HbA, 2) ultraviolet resonance Raman spectroscopy detects alterations in Tyr hydrogen bonding, in Trp hydrophobicity at the ␣ 1 ␤ 2 interface (␤37), and in the A-helix (␣14/␤15) of both chains, 3) displacement by inositol hexaphosphate of the Hb-bound 8-hydroxy-1,3,6-pyrenetrisulfonate (the fluorescent 2,3-diphosphoglycerate analog) follows the order HbA > HbS > HbC, and 4) oxygen equilibria measurements indicate a differential allosteric effect by inositol hexaphosphate for HbC ϳ HbS > HbA.Naturally occurring ␤6 hemoglobin mutants aggregate into defined structures in the erythrocyte. Sickle cell hemoglobin (HbS, ␤6 Glu 3 Val) forms polymers in the deoxy state, whereas HbC (␤6 Glu 3 Lys) forms crystals in the oxy liganded state. A complete understanding of the mechanisms giving rise to deoxy HbS polymers and oxy HbC crystals remains to be elucidated. In the last few years, our laboratory has pursued questions related to mechanisms involved in the ligand-specific, induced crystallization of HbC, starting with site-specific probing of the R-state tetrameric structure of HbC (1, 2). Here, we extend the studies to include a comparison of the R-state of HbS. The R-state of HbS is of particular relevance because oxy HbS exhibits unusual properties compared with HbA, such as mechanical precipitability (3-5), greater unfolding at an airwater interface (6, 7), and increased autooxidation (8 -10).According to existing crystallographic evidence, HbS, HbC, and HbA have essentially the same molecular structure. However, this ignores the following: 1) important areas of the molecule are not well defined crystallographically (e.g. the N-terminal nonhelical portion of the ␣ and ␤ chains), and 2) crystals might constrain conformation compared with that in solution.Spectroscopic and biochemical findin...

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Section: Discussionsupporting

confidence: 76%

Solution-active Structural Alterations in Liganded Hemoglobins C (β6 Glu → Lys) and S (β6 Glu → Val)

Hirsch¹,

Juszczak²,

Fataliev³

et al. 1999

Journal of Biological Chemistry

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“…These regions are characterized by bands that have been described previously. 13 The CD spectra of oxygenated HbIV and HbI are very similar, with the same differences in position and ellipticity of the characteristic bands. These spectra resemble the dichroic characteristics of many other oxy-hemoglobins, such as, e.g., HbA and Hbs from the mollusc Scapharca inequivalvis.…”

Section: Resultsmentioning

confidence: 91%

Steady-state fluorescence and circular dichroism of trout hemoglobins I and IV interacting with tributyltin

et al. 1999

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The effect of tributyltin chloride (TBTC) on rainbow trout (Salmo irideus) hemoglo-bin I (HbI) and hemoglobin IV (HbIV) was characterized by the steady-state fluorescence of intrinsic and extrinsic fluorescent probes. The fluorescence emission spectrum (ex 280 nm) is greatly increased in intensity by the presence of the organotin in both proteins. Circular dichroism spectra in the same samples show a small decrease in 222 , a measure correlated with the percentage of the-helical content. Morever, important changes in near-UV, Soret, and visible regions of CD were induced by TBTC. The correlation of data obtained with trout hemoglo-bins (HbI and HbIV) with similar measurements on globins suggests that the presence of heme is necessary for the interaction of the organotin compound with the proteins. Proteins 1999;34:443-452. 1999 Wiley-Liss, Inc.

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“…The 285-nm CD region is sensitive to R/T-specific differences at the ␣1␤2 inter- face, specifically ␤Trp-37 and ␣Tyr-42, whereas the Sôret bands (410 -450) and the 500 -600-nm region reports on changes in the heme environment (76). The R/T-sensitive regions of the CD spectra are superimposable such that there was no discernable difference between HbE and HbA for both the deoxy and CO derivatives (data not shown).…”

Section: Structural Studiesmentioning

confidence: 99%

Structural and Functional Studies Indicating Altered Redox Properties of Hemoglobin E

Roche

Malashkevich

Balazs

et al. 2011

Journal of Biological Chemistry

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Hemoglobin (Hb) E (␤-Glu26Lys) remains an enigma in terms of its contributions to red blood cell (RBC) pathophysiological mechanisms; for example, EE individuals exhibit a mild chronic anemia, and HbE/␤-thalassemia individuals show a range of clinical manifestations, including high morbidity and death, often resulting from cardiac dysfunction.The purpose of this study was to determine and evaluate structural and functional consequences of the HbE mutation that might account for the pathophysiology. Functional studies indicate minimal allosteric consequence to both oxygen and carbon monoxide binding properties of the ferrous derivatives of HbE. In contrast, redoxsensitive reactions are clearly impacted as seen in the following: 1) the ϳ2.5 times decrease in the rate at which HbE catalyzes nitrite reduction to nitric oxide (NO) relative to HbA, and 2) the accelerated rate of reduction of aquometHbE by L-cysteine (L-Cys). Sol-gel encapsulation studies imply a shift toward a higher redox potential for both the T and R HbE structures that can explain the origin of the reduced nitrite reductase activity of deoxyHbE and the accelerated rate of reduction of aquometHbE by cysteine. Deoxy-and CO HbE crystal structures (derived from crystals grown at or near physiological pH) show loss of hydrogen bonds in the microenvironment of ␤Lys-26 and no significant tertiary conformational perturbations at the allosteric transition sites in the R and T states. Together, these data suggest a model in which the HbE mutation, as a consequence of a relative change in redox properties, decreases the overall rate of Hb-mediated production of bioactive NO.

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[17] Circular dichroism spectra of hemoglobins

Cited by 53 publications

References 36 publications

Solution-active Structural Alterations in Liganded Hemoglobins C (β6 Glu → Lys) and S (β6 Glu → Val)

Solution-active Structural Alterations in Liganded Hemoglobins C (β6 Glu → Lys) and S (β6 Glu → Val)

Steady-state fluorescence and circular dichroism of trout hemoglobins I and IV interacting with tributyltin

Structural and Functional Studies Indicating Altered Redox Properties of Hemoglobin E

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