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Sub-cellular Biochemistry 2020This chapter reviews how allosteric (heterotrophic) effectors and natural mutations impact hemoglobin (Hb) primary physiological function of oxygen binding and... (Review)
Review
This chapter reviews how allosteric (heterotrophic) effectors and natural mutations impact hemoglobin (Hb) primary physiological function of oxygen binding and transport. First, an introduction about the structure of Hb is provided, including the ensemble of tense and relaxed Hb states and the dynamic equilibrium of Hb multistate. This is followed by a brief review of Hb variants with altered Hb structure and oxygen binding properties. Finally, a review of different endogenous and exogenous allosteric effectors of Hb is presented with particular emphasis on the atomic interactions of synthetic ligands with altered allosteric function of Hb that could potentially be harnessed for the treatment of diseases.
Topics: Allosteric Regulation; Hematologic Diseases; Hemoglobins; Humans; Ligands; Oxygen
PubMed: 32189307
DOI: 10.1007/978-3-030-41769-7_14 -
Cold Spring Harbor Perspectives in... Mar 2013Diseases affecting hemoglobin synthesis and function are extremely common worldwide. More than 1000 naturally occurring human hemoglobin variants with single amino acid... (Review)
Review
Diseases affecting hemoglobin synthesis and function are extremely common worldwide. More than 1000 naturally occurring human hemoglobin variants with single amino acid substitutions throughout the molecule have been discovered, mainly through their clinical and/or laboratory manifestations. These variants alter hemoglobin structure and biochemical properties with physiological effects ranging from insignificant to severe. Studies of these mutations in patients and in the laboratory have produced a wealth of information on hemoglobin biochemistry and biology with significant implications for hematology practice. More generally, landmark studies of hemoglobin performed over the past 60 years have established important paradigms for the disciplines of structural biology, genetics, biochemistry, and medicine. Here we review the major classes of hemoglobin variants, emphasizing general concepts and illustrative examples.
Topics: Hemoglobinopathies; Hemoglobins; Hemoglobins, Abnormal; Humans; Methemoglobin; Mutation; Oxygen
PubMed: 23388674
DOI: 10.1101/cshperspect.a011858 -
Singapore Medical Journal Aug 2010Glycated haemoglobins are haemoglobins with an attached sugar moiety. They constitute the HbA1 fraction of the adult haemoglobin HbA. HbA1c is the predominant fraction... (Review)
Review
Glycated haemoglobins are haemoglobins with an attached sugar moiety. They constitute the HbA1 fraction of the adult haemoglobin HbA. HbA1c is the predominant fraction of HbA1 and gives an estimate of the blood sugar levels of an individual over the last three months. It has been observed that an HbA1c value of less than seven percent reduces the microvascular complications in diabetic patients. However, HbA1c is not affected by blood sugar levels alone. Apart from blood sugar, there are other factors that affect HbA1c. This article reviews in detail the structure, formation, methods of measurement, factors affecting HbA1c levels and their clinical significance.
Topics: Blood Glucose; Diabetes Mellitus; Glycated Hemoglobin; Humans
PubMed: 20848057
DOI: No ID Found -
Journal of Medical Genetics Mar 1965
Review
Topics: Genetics, Medical; Hemoglobins; Hemoglobins, Abnormal; Humans
PubMed: 14296925
DOI: 10.1136/jmg.2.1.48 -
Comptes Rendus Biologies Dec 2002Haemoglobins from unicellular organisms, plants or animals, share a common structure, which results from the folding, around the heme group, of a polypeptide chain made... (Review)
Review
Haemoglobins from unicellular organisms, plants or animals, share a common structure, which results from the folding, around the heme group, of a polypeptide chain made from 6-8 helices. Nowadays, deciphering the genome of several species allows one to draw the evolutionary tree of this protein going back to 1800 millions of years, at a time when oxygen began to accumulate in the atmosphere. This permits to follow the evolution of the ancestral gene and of its product. It is likely that, only in complex multicellular species, transport and storage of oxygen became the main physiological function of this molecule. In addition, in unicellular organisms and small invertebrates, it is likely that the main function of this protein was to protect the organism from the toxic effect of O2, CO and NO*. The very high oxygen affinity of these molecules, leading them to act rather as a scavenger as an oxygen carrier, supports this hypothesis. Haemoglobins from microorganisms, which may probably be the closest vestiges to the ancestral molecules, are divided into three families. The first one is made from flavohaemoglobins, a group of chimerical proteins carrying a globin domain and an oxido-reduction FAD-dependant domain. The second corresponds to truncated haemoglobins, which are hexacoordinated with very high oxygen-affinity molecules, 20-40 residues shorter than classical haemoglobins. The third group is made from bacterial haemoglobins such as that of Vitreoscilla. Some specific structural arrangements in the region surrounding the heme are cause of their high oxygen affinity. In plants, two types of haemoglobins are present (non-symbiotic and symbiotic), that arose from duplication of an ancestral vegetal gene. Non-symbiotic haemoglobins, which are probably the oldest, are scarcely distributed within tissues having high energetic consumption. Conversely, symbiotic haemoglobins (also named leghaemoglobins) are present at a high concentration (mM) mostly in the rhizomes of legumes, where they are involved in nitrogen metabolism. In some species, haemoglobin was proposed to be an oxygen sensor bringing to the organism information to adjust metabolism or biosynthesis to the oxygen requirement. Elsewhere haemoglobin may act as final electron acceptors in oxido-reduction pathways. Evolution of haemoglobin in invertebrates followed a large variety of scenarios. Some surprising functions as sulphide acquisition in invertebrates living near hydrothermal vents, or a role in the phototrophism of worm need to be mentioned. In invertebrates, the size of haemoglobin varies from monomers to giant molecules associating up to 144 subunits, while in vertebrates it is always a tetramer. In some species, several haemoglobins, with completely different structure and function, may coexist. This demonstrates how hazardous may be to extrapolate the function of a protein from only structural data.
Topics: Animals; Bacteria; Evolution, Molecular; Globins; Hemeproteins; Hemoglobins; Humans; Models, Molecular; Oxygen; Phycocyanin; Plants; Protein Folding
PubMed: 12520866
DOI: 10.1016/s1631-0691(02)01537-8 -
Antioxidants & Redox Signaling Jun 2013In the last several years, significant work has been done studying hemoglobin (Hb) oxidative reactions and clearance mechanisms using both in vitro and in vivo model...
In the last several years, significant work has been done studying hemoglobin (Hb) oxidative reactions and clearance mechanisms using both in vitro and in vivo model systems. One active research area involves the study of molecular chaperones and other proteins that are thought to mitigate the toxicity of acellular Hb. For example, the plasma protein haptoglobin (Hp) and the pre-erythroid protein alpha-hemoglobin-stabilizing protein (AHSP) bind to acellular Hb and alpha-subunits of Hb, respectively, to reduce these adverse effects. Moreover, there has been significant work studying hemopexin and alpha-1 microglobulin, both of which are thought to be involved with hemin degradation. These studies have coincided with the timely publication of the first crystal structure of the Hb-Hp complex. In constructing this Forum, we have invited a number of researchers in the area of Hb and myoglobin (Mb) redox biochemistry, as well as those who have contributed fundamentally to our knowledge of Hp function. Our goal has been to update this critically important research area, because we believe that it will ultimately impact the practice of transfusion medicine in a number of important ways.
Topics: Animals; Hemoglobins; Humans; Oxidation-Reduction
PubMed: 23330885
DOI: 10.1089/ars.2013.5195 -
Experimental Physiology Jan 2008Myoglobin and haemoglobin, the respiratory pigments of mammals and some molluscs, annelids and arthropods, belong to an ancient superfamily of haem-associated globin... (Review)
Review
Myoglobin and haemoglobin, the respiratory pigments of mammals and some molluscs, annelids and arthropods, belong to an ancient superfamily of haem-associated globin proteins. Members of this family share common structural and spectral features. They also share some general functional characteristics, such as the ability to bind ligands, e.g. O2, CO and NO, at the iron atom and to undergo redox changes. These properties are used in vivo to perform a wide range of biochemical and physiological roles. While it is acknowledged that the major role of haemoglobin is to bind oxygen reversibly and deliver it to the tissues, this is not its only function, while the often-stated role of myoglobin as an oxygen storage protein is possibly a misconception. Furthermore, haemoglobin and myoglobin express enzymic activities that are important to their function, e.g. NO dioxygenase activity or peroxidatic activity that may be partly responsible for pathophysiology following haemorrhage. Evidence for these functions is described, and the discussion extended to include proteins that have recently been discovered and that are expressed at low levels within the cell. These proteins are hexaco-ordinate, unlike haemoglobin and myoglobin, and are widely distributed throughout the animal kingdom (e.g. neuroglobins and cytoglobins). They may have specialist roles in oxygen delivery to particular sites within the cell but may also perform roles associated with O2 sensing and signalling and in responses to stress, e.g. protection from reactive oxygen and nitrogen species. Haemoglobins are also widespread in plants and bacteria and may serve similar protective functions.
Topics: Animals; Enzymes; Heme; Hemoglobins; Humans; Myoglobin; Oxygen; Protein Binding
PubMed: 17981931
DOI: 10.1113/expphysiol.2007.039735 -
IUBMB Life May 2022Hemoglobin oxidation due to oxidative stress and disease conditions leads to the generation of ROS (reactive oxygen species) and membrane attachment of hemoglobin...
Hemoglobin oxidation due to oxidative stress and disease conditions leads to the generation of ROS (reactive oxygen species) and membrane attachment of hemoglobin in-vivo, where its redox activity leads to peroxidative damage of membrane lipids and proteins. Spectrin, the major component of the red blood cell (RBC) membrane skeleton, is known to interact with hemoglobin and, here this interaction is shown to increase hemoglobin peroxidase activity in the presence of reducing substrate ABTS (2', 2'-Azino-Bis-3-Ethylbenzothiazoline-6-Sulfonic Acid). It is also shown that in the absence of reducing substrate, spectrin forms covalently cross-linked aggregates with hemoglobin which display no peroxidase activity. This may have implications in the clearance of ROS and limiting peroxidative damage. Spectrin is found to modulate the peroxidase activity of different hemoglobin variants like A, E, and S, and of isolated globin chains from each of these variants. This may be of importance in disease states like sickle cell disease and HbE-β-thalassemia, where increased oxidative damage and free globin subunits are present due to the defects inherent in the hemoglobin variants associated with these diseases. This hypothesis is corroborated by lipid peroxidation experiments. The modulatory role of spectrin is shown to extend to other heme proteins, namely catalase and cytochrome-c. Experiments with free heme and Raman spectroscopy of heme proteins in the presence of spectrin show that structural alterations occur in the heme moiety of the heme proteins on spectrin binding, which may be the structural basis of increased enzyme activity.
Topics: Antioxidants; Catalase; Heme; Hemeproteins; Hemoglobins; Peroxidase; Peroxidases; Reactive Oxygen Species; Spectrin
PubMed: 35184374
DOI: 10.1002/iub.2607 -
Endocrinology, Diabetes & Metabolism Oct 2021A high haemoglobin glycation index (HGI) is associated with greater risk for hypoglycaemia and chronic vascular disease. Standardizing how the HGI is calculated would...
AIMS
A high haemoglobin glycation index (HGI) is associated with greater risk for hypoglycaemia and chronic vascular disease. Standardizing how the HGI is calculated would normalize results between research studies and hospital laboratories and facilitate the clinical use of HGI for assessing risk.
METHODS
The HGI is the difference between an observed HbA1c and a predicted HbA1c obtained by inserting fasting plasma glucose (FPG) into a regression equation describing the linear relationship between FPG and HbA1c in a reference population. We used data from the 2005-2016 U.S. National Health and Nutrition Examination Survey (NHANES) to identify a reference population of 18,675 diabetes treatment-naïve adults without self-reported diabetes. The reference population regression equation (predicted HbA1c = 0.024 FPG + 3.1) was then used to calculate the HGI and divide participants into low (<-0.150), moderate (-0.150 to <0.150) and high (≥0.150) HGI subgroups. Diabetes status was classified by OGTTs.
RESULTS
As previously reported in multiple studies, a high HGI was associated with black race independent of diabetes status, and with older age, higher BMI and higher CRP in normal and prediabetic but not diabetic participants. The mean HGI was 0.6% higher in self-reported diabetic adults. The HGI was not associated with plasma insulin, HOMA-IR or 2 h OGTT in participants classified as normal, prediabetic or diabetic.
CONCLUSIONS
The regression equation derived from this demographically diverse diabetes treatment-naïve adult NHANES reference population is suitable for standardizing how the HGI is calculated for both clinical use and in research to mechanistically explain population variation in the HGI and why a high HGI is associated with greater risk for chronic vascular disease.
Topics: Adult; Diabetes Mellitus, Type 2; Glucose Tolerance Test; Glycated Hemoglobin; Hemoglobins; Humans; Nutrition Surveys
PubMed: 34558807
DOI: 10.1002/edm2.299 -
Resolvability of free energy changes for oxygen binding and subunit association by human hemoglobin.Biophysical Journal Jul 1989Probability distributions of the free energy changes for oxygen binding, subunit association, and quaternary enhancement by human hemoglobin were obtained from Monte...
Probability distributions of the free energy changes for oxygen binding, subunit association, and quaternary enhancement by human hemoglobin were obtained from Monte Carlo simulations performed on two independent sets of variable protein concentration equilibrium oxygen-binding data. Uncertainties in unliganded and fully liganded dimer to tetramer association free energy changes (0 delta G'2 and 4 delta G'2) were accounted for in the simulations. Distributions of the dimer to tetramer association free energy changes for forming singly and triply liganded tetramers (1 delta G'2 and 3 delta G'2) are well defined and quite symmetric, whereas that for forming doubly liganded tetramers (2 delta G'2) is poorly defined and highly asymmetric. The distribution of the dimer stepwise oxygen-binding free-energy change (delta g'2i) is well defined and quite symmetric as are those of the tetramer stepwise oxygen-binding free-energy changes for binding the first and last oxygens to tetramers (delta g'41 and delta g'44). Distributions of the intermediate tetramer stepwise oxygen-binding free-energy changes (delta g'42 and delta g'43) are poorly defined and highly asymmetric, but are compensatory in that their sum (delta g'4[2 + 3]) is again well defined and nearly symmetric. Distributions of the free energy changes corresponding to the tetramer product Adair oxygen binding constants (delta G'4i) are well defined and quite symmetric for i = 1, 3, 4 but not for i = 2. The distribution of delta g'44 - delta g'2i (the quaternary enhancement free energy change) is relatively narrow, nearly symmetric, and confined to the negative free-energy domain. This suggests that the quaternary enhancement free energy change (a) may be resolved with good confidence from this data and (b) is finite and negative under the conditions of these experiments. Our results also suggest two different four-state combinatorial switch models that provide accurate characterization of hemoglobin's functional behavior.
Topics: Hemoglobins; Humans; Macromolecular Substances; Monte Carlo Method; Oxyhemoglobins; Probability; Protein Binding; Thermodynamics
PubMed: 2752084
DOI: 10.1016/S0006-3495(89)82648-7