1
|
Morita Y, Takada R, Saito A, Komatsu T. Genetically and chemically tuned haemoglobin-albumin trimers with superior O 2 transport efficiency. Chem Commun (Camb) 2021; 57:9144-9147. [PMID: 34498647 DOI: 10.1039/d1cc03684j] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Haemoglobin (Hb)-albumin (HSA) trimers were synthesized using five distinct Hb variants in which the structures were genetically and chemically tuned as an artificial O2 carrier and used as a red blood cell (RBC) substitute. The trimers were found to have moderately low O2 affinity (p50 = 23-34 Torr, 37 °C) and high co-operativity, yielding a maximum O2 transport efficiency 1.8-fold higher than that of human RBCs.
Collapse
Affiliation(s)
- Yoshitsugu Morita
- Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan.
| | - Ryoya Takada
- Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan.
| | - Asuka Saito
- Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan.
| | - Teruyuki Komatsu
- Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan.
| |
Collapse
|
2
|
Mañú Pereira MDM, Ropero P, Loureiro C, Vives Corrons JL. Low affinity hemoglobinopathy (Hb Vigo) due to a new mutation of beta globin gene (c200 A>T; Lys>Ile). A cause of rare anemia misdiagnosis. Am J Hematol 2017; 92:E38-E40. [PMID: 28066926 DOI: 10.1002/ajh.24649] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Revised: 01/05/2017] [Accepted: 01/05/2017] [Indexed: 11/07/2022]
|
3
|
Shadrina MS, Peslherbe GH, English AM. O2 and Water Migration Pathways between the Solvent and Heme Pockets of Hemoglobin with Open and Closed Conformations of the Distal HisE7. Biochemistry 2015; 54:5279-89. [PMID: 26226401 DOI: 10.1021/acs.biochem.5b00369] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Hemoglobin transports O2 by binding the gas at its four hemes. Hydrogen bonding between the distal histidine (HisE7) and heme-bound O2 significantly increases the affinity of human hemoglobin (HbA) for this ligand. HisE7 is also proposed to regulate the release of O2 to the solvent via a transient E7 channel. To reveal the O2 escape routes controlled by HisE7 and to evaluate its role in gating heme access, we compare simulations of O2 diffusion from the distal heme pockets of the T and R states of HbA performed with HisE7 in its open (protonated) and closed (neutral) conformations. Irrespective of HisE7's conformation, we observe the same four or five escape routes leading directly from the α- or β-distal heme pockets to the solvent. Only 21-53% of O2 escapes occur via these routes, with the remainder escaping through routes that encompass multiple internal cavities in HbA. The conformation of the distal HisE7 controls the escape of O2 from the heme by altering the distal pocket architecture in a pH-dependent manner, not by gating the E7 channel. Removal of the HisE7 side chain in the GlyE7 variant exposes the distal pockets to the solvent, and the percentage of O2 escapes to the solvent directly from the α- or β-distal pockets of the mutant increases to 70-88%. In contrast to O2, the dominant water route from the bulk solvent is gated by HisE7 because protonation and opening of this residue dramatically increase the rate of influx of water into the empty distal heme pockets. The occupancy of the distal heme site by a water molecule, which functions as an additional nonprotein barrier to binding of the ligand to the heme, is also controlled by HisE7. Overall, analysis of gas and water diffusion routes in the subunits of HbA and its GlyE7 variant sheds light on the contribution of distal HisE7 in controlling polar and nonpolar ligand movement between the solvent and the hemes.
Collapse
Affiliation(s)
- Maria S Shadrina
- Department of Chemistry and Biochemistry, Centre for Research in Molecular Modeling and PROTEO, Concordia University , Montreal, Quebec H4B 1R6, Canada
| | - Gilles H Peslherbe
- Department of Chemistry and Biochemistry, Centre for Research in Molecular Modeling and PROTEO, Concordia University , Montreal, Quebec H4B 1R6, Canada
| | - Ann M English
- Department of Chemistry and Biochemistry, Centre for Research in Molecular Modeling and PROTEO, Concordia University , Montreal, Quebec H4B 1R6, Canada
| |
Collapse
|
4
|
Yang Q, Yu F, Sun L, Zhang Q, Lin M, Geng X, Sun X, Li J, Liu Y. Identification of amino acid residues involved in hemin binding inPorphyromonas gingivalishemagglutinin 2. Mol Oral Microbiol 2015; 30:337-46. [PMID: 25833325 DOI: 10.1111/omi.12097] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/06/2015] [Indexed: 12/01/2022]
Affiliation(s)
- Q.B. Yang
- Beijing Institute for Dental Research; Beijing Stomatological Hospital and School of Stomatology; Capital Medical University; Beijing China
| | - F.Y. Yu
- Beijing Institute for Dental Research; Beijing Stomatological Hospital and School of Stomatology; Capital Medical University; Beijing China
| | - L. Sun
- Beijing Institute for Dental Research; Beijing Stomatological Hospital and School of Stomatology; Capital Medical University; Beijing China
| | - Q.X. Zhang
- Beijing Institute for Dental Research; Beijing Stomatological Hospital and School of Stomatology; Capital Medical University; Beijing China
| | - M. Lin
- Beijing Institute for Dental Research; Beijing Stomatological Hospital and School of Stomatology; Capital Medical University; Beijing China
| | - X.Y. Geng
- Beijing Institute for Dental Research; Beijing Stomatological Hospital and School of Stomatology; Capital Medical University; Beijing China
| | - X.N. Sun
- Beijing Institute for Dental Research; Beijing Stomatological Hospital and School of Stomatology; Capital Medical University; Beijing China
| | - J.L. Li
- Beijing Institute for Dental Research; Beijing Stomatological Hospital and School of Stomatology; Capital Medical University; Beijing China
| | - Y. Liu
- Beijing Institute for Dental Research; Beijing Stomatological Hospital and School of Stomatology; Capital Medical University; Beijing China
| |
Collapse
|
5
|
Miele AE, Bellelli A, Brunori M. Hemoglobin Allostery: New Views on Old Players. J Mol Biol 2013; 425:1515-26. [DOI: 10.1016/j.jmb.2012.12.018] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Revised: 12/18/2012] [Accepted: 12/20/2012] [Indexed: 11/30/2022]
|
6
|
Jia Y, Wood F, Buehler PW, Alayash AI. Haptoglobin preferentially binds β but not α subunits cross-linked hemoglobin tetramers with minimal effects on ligand and redox reactions. PLoS One 2013; 8:e59841. [PMID: 23555800 PMCID: PMC3612097 DOI: 10.1371/journal.pone.0059841] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2012] [Accepted: 02/20/2013] [Indexed: 11/29/2022] Open
Abstract
Human hemoglobin (Hb) and haptoglobin (Hp) exhibit an extremely high affinity for each other, and the dissociation of Hb tetramers into dimers is generally believed to be a prerequisite for complex formation. We have investigated Hp interactions with native Hb, αα, and ββ cross-linked Hb (ααXLHb and ββXLHb, respectively), and rapid kinetics of Hb ligand binding as well as the redox reactivity in the presence of and absence of Hp. The quaternary conformation of ββ subunit cross-linking results in a higher binding affinity than that of αα subunit cross-linked Hb. However, ββ cross-linked Hb exhibits a four fold slower association rate constant than the reaction rate of unmodified Hb with Hp. The Hp contact regions in the Hb dimer interfaces appear to be more readily exposed in ββXLHb than ααXLHb. In addition, apart from the functional changes caused by chemical modifications, Hp binding does not induce appreciable effects on the ligand binding and redox reactions of ββXLHb. Our findings may therefore be relevant to the design of safer Hb-based oxygen therapeutics by utilizing this preferential binding of ββXLHb to Hp. This may ultimately provide a safe oxidative inactivation and clearance pathway for chemically modified Hbs in circulation.
Collapse
Affiliation(s)
- Yiping Jia
- Laboratory of Biochemistry and Vascular Biology, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland, United States of America.
| | | | | | | |
Collapse
|
7
|
Banerjee S, Jia Y, Siburt CJP, Abraham B, Wood F, Bonaventura C, Henkens R, Crumbliss AL, Alayash AI. Haptoglobin alters oxygenation and oxidation of hemoglobin and decreases propagation of peroxide-induced oxidative reactions. Free Radic Biol Med 2012; 53:1317-26. [PMID: 22841869 DOI: 10.1016/j.freeradbiomed.2012.07.023] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2012] [Revised: 07/17/2012] [Accepted: 07/19/2012] [Indexed: 01/18/2023]
Abstract
We compared oxygenation and anaerobic oxidation reactions of a purified complex of human hemoglobin (Hb) and haptoglobin (Hb-Hp) to those of uncomplexed Hb. Under equilibrium conditions, Hb-Hp exhibited active-site heterogeneity and noncooperative, high-affinity O(2) binding (n(1/2)=0.88, P(1/2)=0.33 mm Hg in inorganic phosphate buffer at pH 7 and 25 °C). Rapid-reaction kinetics also exhibited active-site heterogeneity, with a slower process of O(2) dissociation and a faster process of CO binding relative to uncomplexed Hb. Deoxygenated Hb-Hp had significantly reduced absorption at the λ(max) of 430 nm relative to uncomplexed Hb, as occurs for isolated Hb subunits that lack T-state stabilization. Under comparable experimental conditions, the redox potential (E(1/2)) of Hb-Hp was found to be +54 mV, showing that it is much more easily oxidized than uncomplexed Hb (E(1/2)=+125 mV). The Nernst plots for Hb-Hp oxidation showed no cooperativity and slopes less than unity indicated active-site heterogeneity. The redox potential of Hb-Hp was unchanged by pH over the range of 6.4-8.3. Exposure of Hb-Hp to excess hydrogen peroxide (H(2)O(2)) produced ferryl heme, which was found to be more kinetically inert in the Hb-Hp complex than in uncomplexed Hb. The negative shift in the redox potential of Hb-Hp and its stabilized ferryl state may be central elements in the protection against Hb-induced oxidative damage afforded by formation of the Hb-Hp complex.
Collapse
Affiliation(s)
- Sambuddha Banerjee
- Chemistry Department, French Family Science Center, Box 90346, Duke University, Durham, NC 27708-0346, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
8
|
Roche CJ, Dantsker D, Alayash AI, Friedman JM. Enhanced nitrite reductase activity associated with the haptoglobin complexed hemoglobin dimer: functional and antioxidative implications. Nitric Oxide 2012; 27:32-9. [PMID: 22521791 DOI: 10.1016/j.niox.2012.04.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2012] [Revised: 03/29/2012] [Accepted: 04/11/2012] [Indexed: 10/28/2022]
Abstract
The presence of acellular hemoglobin (Hb) within the circulation is generally viewed as a pathological state that can result in toxic consequences. Haptoglobin (Hp), a globular protein found in the plasma, binds with high avidity the αβ dimers derived from the dissociation of Hb tetramer and thus helps clear free Hb. More recently there have been compelling indications that the redox properties of the Hp bound dimer (Hb-Hp) may play a more active role in controlling toxicity by limiting the potential tissue damage caused by propagation of the free-radicals generated within the heme containing globin chains. The present study further examines the potential protective effect of Hp through its impact on the production of nitric oxide (NO) from nitrite through nitrite reductase activity of the Hp bound αβ Hb dimer. The presented results show that the Hb dimer in the Hb-Hp complex has oxygen binding, CO recombination and spectroscopic properties consistent with an Hb species having properties similar to but not exactly the same as the R quaternary state of the Hb tetramer. Consistent with these observations is the finding that the initial nitrite reductase rate for Hb-Hp is approximately ten times that of HbA under the same conditions. These results in conjunction with the earlier redox properties of the Hb-Hp are discussed in terms of limiting the pathophysiological consequences of acellular Hb in the circulation.
Collapse
Affiliation(s)
- Camille J Roche
- Department of Physiology and Biophysics, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | | | | | | |
Collapse
|
9
|
Esquerra RM, Jensen RA, Bhaskaran S, Pillsbury ML, Mendoza JL, Lintner BW, Kliger DS, Goldbeck RA. The pH dependence of heme pocket hydration and ligand rebinding kinetics in photodissociated carbonmonoxymyoglobin. J Biol Chem 2008; 283:14165-75. [PMID: 18359768 DOI: 10.1074/jbc.m709710200] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We monitored the occupancy of a functionally important non-coordinated water molecule in the distal heme pocket of sperm whale myoglobin over the pH range 4.3-9.4. Water occupancy was assessed by using time-resolved spectroscopy to detect the perturbation of the heme visible band absorption spectrum caused by water entry after CO photodissociation ( Goldbeck, R. A., Bhaskaran, S., Ortega, C., Mendoza, J. L., Olson, J. S., Soman, J., Kliger, D. S., and Esquerra, R. M. (2006) Proc. Natl. Acad. Sci. U. S. A. 103, 1254-1259 ). We found that the water occupancy observed during the time interval between ligand photolysis and diffusive recombination decreased by nearly 20% as the pH was lowered below 6. This decrease accounted for most of the concomitant increase in the observed CO bimolecular recombination rate constant, as the lower water occupancy presented a smaller kinetic barrier to CO entry into the pocket at lower pH. These results were consistent with a model in which the distal histidine, which stabilizes the water molecule within the distal pocket by accepting a hydrogen bond, tends to swing out of the pocket upon protonation and destabilize the water occupancy at low pH. Extrapolation of this model to lower pH suggests that the additional increase in ligand association rate constant observed previously in stopped-flow studies at pH 3 may also be due in part to reduced distal water occupancy concomitant with further His64 protonation and coupled protein conformational change.
Collapse
Affiliation(s)
- Raymond M Esquerra
- Department of Chemistry and Biochemistry, San Francisco State University, San Francisco, California 94132, USA.
| | | | | | | | | | | | | | | |
Collapse
|
10
|
Structure and function of sheep hemoglobin Chios: A novel allele at the HBBB locus with two Lys-->Arg substitutions at positions beta66(E10) and beta144(HC1). COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY D-GENOMICS & PROTEOMICS 2007; 2:84-90. [PMID: 20483281 DOI: 10.1016/j.cbd.2007.01.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2006] [Revised: 01/02/2007] [Accepted: 01/02/2007] [Indexed: 11/22/2022]
Abstract
A novel hemoglobin variant was observed in pure sheep (Ovis aries) breeds of the island of Chios (Greece), Egypt and Hungary. This silent variant was identified by gel electrophoresis and RP-HPLC of dissociated globin chains. Two Arg for Lys substitutions were detected, by means of MALDI TOF electrospray mass spectrometric analysis for the intact globins, at positions beta66(E10) and beta144(HC1) of a globin chain having the sequence of the beta(B) chain. Sequencing of the beta-globin gene confirmed the variant gene as being an allele of the HBBB locus having the AAG-->AGG and the AAA-->AGA mutations at codons 66 and 144, respectively, both corresponding to the Lys-->Arg substitution. The intrinsic oxygen affinity of the variant Hb (logP(50)=0.79 at pH 7.0) was found to be intermediate between that of the sheep Hb B (logP(50)=0.92) and that of Cypriot mouflon (O. a. ophion) Hb (logP(50)=0.53), the latter having only the Lys-->Arg change at beta144, whereas nearly no differences were observed in the presence of the Cl(-) physiological effector. Result supports the indication that Arg at beta144 enhances the role of the ligand in decreasing oxygen affinity, this effect being partially counteracted when Arg is at beta66. Data also shows that the Lys-->Arg change at beta66 is responsible for 1.49 fold reduction in the intrinsic oxygen affinity. This hitherto undescribed variant increases to seven the number of alleles at the sheep HBBB locus. Following the nomenclature used for human Hb variants, the new allele was termed as the Hb Chios or [beta(B)66(E10) Lys-->Arg, 144(HC1)Lys-->Arg], whereas the proposed genetic nomenclature of the locus is HBBK.
Collapse
|
11
|
Friess U, Beck A, Kohne E, Lehmann R, Koch S, Haring HU, Schmuelling RM, Schleicher E. Novel hemoglobin variant [beta66(E10) Lys-->Asn], with decreased oxygen affinity, causes falsely low hemoglobin A1c values by HPLC. Clin Chem 2003; 49:1412-5. [PMID: 12881463 DOI: 10.1373/49.8.1412] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Ulrich Friess
- Department of Medicine IV (Endocrinology, Metabolism, and Clinical Chemistry), University of Tuebingen, Otfried-Mueller-Strasse 10, D-72076 Tuebingen, Germany.
| | | | | | | | | | | | | | | |
Collapse
|
12
|
Taboy CH, Faulkner KM, Kraiter D, Bonaventura C, Crumbliss AL. Concentration-dependent effects of anions on the anaerobic oxidation of hemoglobin and myoglobin. J Biol Chem 2000; 275:39048-54. [PMID: 10984477 DOI: 10.1074/jbc.m004547200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The redox potentials of hemoglobin and myoglobin and the shapes of their anaerobic oxidation curves are sensitive indicators of globin alterations surrounding the active site. This report documents concentration-dependent effects of anions on the ease of anaerobic oxidation of representative hemoglobins and myoglobins. Hemoglobin (Hb) oxidation curves reflect the cooperative transition from the T state of deoxyHb to the more readily oxidized R-like conformation of metHb. Shifts in the oxidation curves for Hb A(0) as Cl(-) concentrations are increased to 0.2 m at pH 7.1 indicate preferential anion binding to the T state and destabilization of the R-like state of metHb, leading to reduced cooperativity in the oxidation process. A dramatic reversal of trend occurs above 0.2 m Cl(-) as anions bind to lower affinity sites and shift the conformational equilibrium toward the R state. This pattern has been observed for various hemoglobins with a variety of small anions. Steric rather than electronic effects are invoked to explain the fact that no comparable reversal of oxygen affinity is observed under identical conditions. Evidence is presented to show that increases in hydrophilicity in the distal heme pocket can decrease oxygen affinity via steric hindrance effects while increasing the ease of anaerobic oxidation.
Collapse
Affiliation(s)
- C H Taboy
- Department of Chemistry, Duke University, Durham, North Carolina 27708-0346, USA
| | | | | | | | | |
Collapse
|
13
|
Baudin-Creuza V, Vasseur-Godbillon C, Griffon N, Kister J, Kiger L, Poyart C, Marden MC, Pagnier J. Additive effects of beta chain mutations in low oxygen affinity hemoglobin betaF41Y,K66T. J Biol Chem 1999; 274:25550-4. [PMID: 10464287 DOI: 10.1074/jbc.274.36.25550] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In order to decrease significantly the oxygen affinity of human hemoglobin, we have associated the mutation betaF41Y with another point mutation also known to decrease the oxygen affinity of Hb. We have synthesized a recombinant Hb (rHb) with two mutations in the beta chains: rHb betaF41Y,K66T. In the absence of 2, 3-diphosphoglycerate, additive effects of the mutations are evident, since the doubly mutated Hb exhibits a larger decrease in oxygen affinity than for the individual single mutations. In the presence of 2,3-diphosphoglycerate, the second mutation did not significantly increase the P(50) value relative to the single mutations. However, the kinetics of CO binding still indicate combined effects on the allosteric equilibrium, as evidenced by more of the slow bimolecular phase characteristic of binding to the deoxy conformation. Dimer-tetramer equilibrium studies indicate an increase in stability of the mutants relative to rHb A; the double mutant rHb betaF41Y, K66T at pH 7.5 showed a K(4,2) value of 0.26 microM. Despite the lower oxygen affinity, the single mutant betaF41Y and double mutant betaF41Y,K66T show only a moderate increase of 20% in the autoxidation rate. These mutations are thus of interest in developing a Hb-based blood substitute.
Collapse
Affiliation(s)
- V Baudin-Creuza
- INSERM, Unité 473, 84 rue du Général Leclerc, 94276 Le Kremlin-Bicêtre Cedex, France.
| | | | | | | | | | | | | | | |
Collapse
|
14
|
Bonaventura C, Bonaventura J, Shih DT, Iben ET, Friedman J. Altered ligand rebinding kinetics due to distal-side effects in hemoglobin chico (Lysbeta66(E10) --> thr). J Biol Chem 1999; 274:8686-93. [PMID: 10085107 DOI: 10.1074/jbc.274.13.8686] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Hb Chico is an unusual human hemoglobin variant that has lowered oxygen affinity, but unaltered cooperativity and anion sensitivity. Previous studies showed these features to be associated with distal-side heme pocket alterations that confer increased structural rigidity on the molecule and that increase water content in the beta-chain heme pocket. We report here that the extent of nanosecond geminate rebinding of oxygen to the variant and its isolated beta-chains is appreciably decreased. Structural alterations in this variant decrease its oxygen recombination rates without significantly altering rates of migration out of the heme pocket. Data analysis indicates that one or more barriers that impede rebinding of oxygen from docking sites in the heme pocket are increased, with less consequence for CO rebinding. Resonance Raman spectra show no significant alterations in spectral regions sensitive to interactions between the heme iron and the proximal histidine residue, confirming that the functional differences in the variant are due to distal-side heme pocket alterations. These effects are discussed in the context of a schematic representation of heme pocket wells and barriers that could aid the design of novel hemoglobins with altered ligand affinity without loss of the normal allosteric responses that facilitate unloading of oxygen to respiring tissues.
Collapse
Affiliation(s)
- C Bonaventura
- Duke University Marine/Freshwater Biomedical Center, School of the Environment Marine Laboratory, Beaufort, North Carolina 28516, USA.
| | | | | | | | | |
Collapse
|
15
|
Griffon N, Baudin V, Dieryck W, Dumoulin A, Pagnier J, Poyart C, Marden MC. Tetramer-dimer equilibrium of oxyhemoglobin mutants determined from auto-oxidation rates. Protein Sci 1998; 7:673-80. [PMID: 9541399 PMCID: PMC2143954 DOI: 10.1002/pro.5560070316] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
One of the main difficulties with blood substitutes based on hemoglobin (Hb) solutions is the auto-oxidation of the hemes, a problem aggravated by the dimerization of Hb tetramers. We have employed a method to study the oxyHb tetramer-dimer equilibrium based on the rate of auto-oxidation as a function of protein concentration. The 16-fold difference in dimer and tetramer auto-oxidation rates (in 20 mM phosphate buffer at pH 7.0, 37 degrees C) was exploited to determine the fraction dimer. The results show a transition of the auto-oxidation rate from low to high protein concentrations, allowing the determination of the tetramer-dimer dissociation coefficient K4,2 = [Dimer] 2/[Tetramer]. A 14-fold increase in K4,2 was observed for addition of 10 mM of the allosteric effector inositol hexaphosphate (IHP). Recombinant hemoglobins (rHb) were genetically engineered to obtain Hb with a lower oxygen affinity than native Hb (Hb A). The rHb alpha2beta2 [(C7) F41Y/(G4) N102Y] shows a fivefold increase in K4,2 at pH 7.0, 37 degrees C. An atmosphere of pure oxygen is necessary in this case to insure fully oxygenated Hb. When this condition is satisfied, this method provides an efficient technique to characterize both the tetramer-dimer equilibrium and the auto-oxidation rates of various oxyHb. For low oxygen affinity Hb equilibrated under air, the presence of deoxy subunits accelerates the auto-oxidation. Although a full analysis is complicated, the auto-oxidation studies for air equilibrated samples are more relevant to the development of a blood substitute based on Hb solutions. The double mutants, rHb alpha2beta2 [(C7) F41Y/(G4) N102A] and rHb alpha2beta2 [(C7) F41Y/(E10) K66T], show a lower oxygen affinity and a higher rate of oxidation than Hb A. Simulations of the auto-oxidation rate versus Hb concentration indicate that very high protein concentrations are required to observe the tetramer auto-oxidation rate. Because the dimers oxidize much more rapidly, even a small fraction dimer will influence the observed oxidation rate.
Collapse
Affiliation(s)
- N Griffon
- Institut National de la Santé et de la Recherche Médicale, Unité 473, Hôpital de Bicêtre, Le Kremlin-Bicêtre, France
| | | | | | | | | | | | | |
Collapse
|
16
|
Pechik I, Ji X, Fidelis K, Karavitis M, Moult J, Brinigar WS, Fronticelli C, Gilliland GL. Crystallographic, molecular modeling, and biophysical characterization of the valine beta 67 (E11)-->threonine variant of hemoglobin. Biochemistry 1996; 35:1935-45. [PMID: 8639677 DOI: 10.1021/bi9519967] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The crystal structure of the mutant deoxyhemoglobin in which the beta-globin Val67(E11) has been replaced with threonine [Fronticelli et al. (1993) Biochemistry 32, 1235-1242] has been determined at 2.2 A resolution. Prior to the crystal structure determination, molecular modeling indicated that the Thr67(E11) side chain hydroxyl group in the distal beta-heme pocket forms a hydrogen bond with the backbone carbonyl of His63(E7) and is within hydrogen-bonding distance of the N delta of His63(E7). The mutant crystal structure indicates only small changes in conformation in the vicinity of the E11 mutation confirming the molecular modeling predictions. Comparison of the structures of the mutant beta-subunits and recombinant porcine myoglobin with the identical mutation [Cameron et al. (1993) Biochemistry 32, 13061-13070] indicates similar conformations of residues in the distal heme pocket, but there is no water molecule associated with either of the threonines of the beta-subunits. The introduction of threonine into the distal heme pocket, despite having only small perturbations in the local structure, has a marked affect on the interaction with ligands. In the oxy derivative there is a 2-fold decrease in O2 affinity [Fronticelli et al. (1993) Biochemistry 32, 1235-1242], and the rate of autoxidation is increased by 2 orders of magnitude. In the CO derivative the IR spectrum shows modifications with respect to that of normal human hemoglobin, suggesting the presence of multiple CO conformers. In the nitrosyl derivative an interaction with the O gamma atom of Thr67(E11) is probably responsible for the 10-fold increase in the rate of NO release from the beta-subunits. In the aquomet derivative there is a 6-fold decrease in the rate of hemin dissociation suggesting an interaction of the Fe-coordinated water with the O gamma of Thr67(E11).
Collapse
Affiliation(s)
- I Pechik
- Center for Advanced Research in Biotechnology, University of Maryland Biotechnology Institute, Rockville 20850, USA
| | | | | | | | | | | | | | | |
Collapse
|
17
|
Mathews AJ, Olson JS. Assignment of rate constants for O2 and CO binding to alpha and beta subunits within R- and T-state human hemoglobin. Methods Enzymol 1994; 232:363-86. [PMID: 8057869 DOI: 10.1016/0076-6879(94)32055-1] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
|
18
|
Fronticelli C, Brinigar WS, Olson JS, Bucci E, Gryczynski Z, O'Donnell JK, Kowalczyk J. Recombinant human hemoglobin: modification of the polarity of the beta-heme pocket by a valine67(E11)-->threonine mutation. Biochemistry 1993; 32:1235-42. [PMID: 8448134 DOI: 10.1021/bi00056a006] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Using the mutagenesis and a gene expression system previously described [Fronticelli et al. (1991) J. Protein Chem. 10, 495-501], we have replaced Val67E11 in the distal heme pocket of the beta-chains of hemoglobin with Thr. The valine to threonine substitution is isosteric and only modifies the polarity of the beta-heme environment. The absorption and CD spectra of the resultant mutant hemoglobin were essentially the same as that of wild-type protein, indicating that the mutation did not cause any large conformational changes and that a water molecule was not coordinated to the ferrous iron atom. Equilibrium measurements of oxygen binding to the mutant indicate a 2-fold decrease in overall affinity relative to native or wild-type human hemoglobin. Thermodynamic analyses of O2 binding curves, based either on the sequential Adair model or on the MWC two-state model, indicated that the overall decrease of O2 affinity in the system was due to a lower association equilibrium constant for the intermediates of oxygenation, particularly those involved at the third ligation step. The functional characteristics of the mutant hemoglobin in either the T- or R-state were not modified greatly by the mutation; however, the Bohr effect and sensitivity to C1- were increased, suggesting a role of the intermediates of oxygenation in the modulation of these parameters.(ABSTRACT TRUNCATED AT 250 WORDS)
Collapse
Affiliation(s)
- C Fronticelli
- Department of Biological Chemistry, University of Maryland Medical School, Baltimore 21201
| | | | | | | | | | | | | |
Collapse
|