A new hemoglobin variant altering the alpha 1 beta 2 contact: Hb Chemilly alpha 2 beta 2 99(G1)Asp leads to Val

The contribution of hepatic glycogen to lipogenesis was studied in isolated, intact rat hepatocytes. To establish its importance as a substrate for lipogenesis, the glycogen of isolated hepatocytes was prelabelled with 14C from glucose. Evidence is presented that neither glucose nor glycogen constitute major sources of carbon for de novo synthesis of fatty acids and that less than 1% of glycogen is converted into fatty acids.     

Clinicohematologic effects of hemoglobin Altdorf (alpha 2 beta 2 135 Ala replaced by Pro)

Hb Altdorf alpha 2 beta 2 135 Ala leads to Pro is an unstable variant occurring near Lecce in Italy. The abnormal hemoglobin does not separate from Hb A in the electrophoresis. In vitro a marked Heinz body formation is produced with phenylhydrazin. In heterozygous individuals an almost compensated hemolysis and a slight splenomegaly are found. Hemolysis can be aggravated by exogenous factors. A rather severe hemolysis was induced by a viral infection in a 3 years old girl.     

Glycerated hemoglobin, alpha 2A beta 2(82) (EF6) N epsilon-glyceryllysine. A new post-translational modification occurring in erythrocyte bisphosphoglyceromutase deficiency

A new minor Hb fraction initially designated Hbx, has been found in the hemolysate of an erythremic patient that we have previously described with a complete erythrocyte bisphosphoglycerate mutase (EC 5.4.2.4) deficiency. Hbx (3.5% of the total) was detected by isoelectric focusing and exhibited electrophoretic and chromatographic properties similar to those of several variants of the Hb central cavity. By density fractionation of red cells, it was demonstrated that Hbx was an aging hemoglobin as in the case of glycated Hb A1c. Functional studies revealed a low oxygen affinity and almost complete inhibition of the allosteric effect of the organic phosphate effectors. Structural studies demonstrated an absence of tryptic cleavage between the peptides beta T9 and beta T10 suggesting the presence of an adduct on Lys beta 82 or on a neighboring residue. Fast atom bombardment mass spectrometry and a specific enzymatic assay with glyoxylate reductase demonstrated that the beta 82 adduct was a glycerate moiety. It was concluded that Hbx was a glycerylated Hb, alpha 2A beta 2(82) (EF6) N epsilon-glyceryllysine, to our knowledge the first example of glycerylated protein. The mechanism of formation of glyceryl Hb, which was found in the four studied subjects with a bisphosphoglyceromutase deficiency, remains to be determined.     

Hemoglobin Fannin-Lubbock [alpha2 beta 2 119 (GH2) Gly replaced by Asp]. A new hemoglobin variant at the alpha1 beta 1 contact.

Hemoglobin Fannin-Lubbock was found in a 9-year-old Mexican-American female. The abnormal hemoglobin was detected as a fast-moving variant by electrophoresis on cellulose acetate at pH 8.4. Structural analysis indicated a substitution in the beta-chain of aspartic acid for glycine at position 119, a position involved in the alpha1beta1 contact of the hemoglobin tetramer. This contact between unlike chains is larger and undergoes a smaller shift during the process of oxygenation and deoxygenation that the alpha1beta2 contact (Perutz, M.F., Muirhead, H., Cox, J.M. and Goaman, L.C.G. (1968) Nature 219, 131-139). Mutations in this contact tend to cause slight or no changes in functional behavior. Apart from a mild anemia, the propositus did not exhibit any obvious clinical symptoms.     

A new abnormal human hemoglobin: Hb Prato (alpha 2 31 (B12) Arg leads to Ser beta 2).

An abnormal human hemoglobin was found in a hemolysate from a 5-year-old healthy child living in Prato (Tuscany, Italy). Strutctural studies demonstrated a previously unreported amino acid substitution, alpha 31 (B12) Arg leads to Ser (this is an alpha 1 beta 1 contact). The new variant has been named Hb Prato. It was unstable in isopropanol and heat-denaturation tests, but has normal functional properties, with respect to whole blood studies. Family studies indicated that the variant had been inherited from the mother, a 39-year-old woman of Sicilian extraction. Hb Prato occurs at 20 and 28% in hemolysates from the boy and woman, respectively.     

A new hemoglobin variant. HB Yatsushiro alpha 2 A beta 2 60 Val replaced by Leu

This study was performed to establish the structural abnormality of a new hemoglobin variant discover-d in a Japanese patient with angina pectoris. The hybridization of the separated hemoglobin with canine hemoglobin revealed a beta-chain anomaly. Peptide betaTp-6 was found to be abnormally located on the peptide map of tryptic digests of the S-carboxymethylated beta-chain from the variant hemoglobin. A structural study on the abnormal betaTp-6 revealed that the variant hemoglobin differs from hemoglobin A by substitution of leucine for valine at residue 60 of the beta-chain. This new variant hemoglobin is designated as hemoglobin Yatsushiro after the name of the city where the propositus lived. The patient is hematologically healthy and his clinical history has nothing to do with this abnormal hemoglobin.     

Structure and function of Hb Saint-Jacques (alpha 2 beta 2 140 (H18) Ala----Thr): a new high-oxygen-affinity variant with altered bisphosphoglycerate binding

A low P50 value in a fresh red blood cell suspension was discovered in a polycythemic patient (Hb 19 g X dl-1). Routine acid and alkaline electrophoreses of the hemolysate were identical to normal hemolysate. Isoelectrofocusing (pH gradient 6-8) did not reveal any abnormal band whether performed with the fully liganded or deoxygenated samples. Precise analyses of the oxygen dissociation curves of the propositus' red cells demonstrated a biphasic Hill plot, a normal Bohr effect and low interaction with 2,3-bisphosphoglycerate (2,3-DPG). Studies on the unfractionated hemolysate confirmed these observations and the inhibition of the effect of organic phosphates. Structural studies were carried out on the mixture of beta A + beta X chains and revealed the presence of two beta Tp14 peptides. Sequencing the abnormal beta Tp14 peptide showed the substitution Ala----Thr of the beta 140 (H18) residue. This new variant was named Hb Saint-Jacques. Examination of the three dimensional model of HbAo indicates that the substitution beta 140 (H18) Ala----Thr induces van der Waals interactions with the nearby lysine-82 (EF6) and leucine-81 (EF5) and a displacement of the EF corner of the beta chains. This is likely to change the normal position of the lysine-82 (EF6), a major anionic binding site in the central cavity between the two beta chains. Functional studies confirm the interpretation of a steric hindrance inhibiting the binding of large organic phosphates to Hb Saint-Jacques.     

Hb Doha or alpha 2 beta 2[X-N-Met-1(NA1)Val----Glu]; a new beta-chain abnormal hemoglobin observed in a Qatari female

Structural analysis of a fast-moving hemoglobin variant, present in three members of a Qatari family, identified a Val----Glu substitution at position 1 (NA1) of the beta-chain. The introduction of this glutamic acid residue prevents the removal of the initiator methionine, thus extending the N-terminus by one residue to Met-Glu-His-Leu-Thr-. The methionine residue is blocked by an as yet not completely identified molecule. The presence of the variant in a heterozygote does not have clinical consequences.     

Effect of FS (alpha 2 gamma beta s) hybrid hemoglobin on Hb S nucleation and aggregation

Asymmetrical cross-linked FS (alpha 2 gamma beta s) hybrid hemoglobin (Hb FS-fumarate) was prepared by reacting mixtures of hemoglobins F and S with double-headed aspirin, bis(3,5-dibromosalicyl) fumarate. When the molar ratio of hemoglobin to the cross-linking agent was 1 to 2 in a 1:1 FS mixture, the relative ratio of the products, cross-linked hemoglobins F (Hb F-fumarate), FS (HB FS-fumarate), and S (Hb S-fumarate), was 1.0:2.6:2.0, in contrast to a 1:2:1 ratio of cross-linked hemoglobins A, AS, and S in a 1:1 AS mixture. These results suggest that the fumaryl group reacts differently with Hb F, Hb FS and Hb S, and that the difference could be attributed to the difference in the structure in the vicinity of the EF6 Lys of non alpha-chains. The oxygen-binding properties of Hb F-fumarate, Hb FS-fumarate, and Hb S-fumarate were similar, except that the n-value of Hb F-fumarate was slightly lower than n-values of Hb S-fumarate and Hb FS-fumarate. Kinetic studies on aggregation showed that the addition of Hb FS-fumarate to unmodified Hb S did not affect the delay time prior to aggregation, but did increase the total turbidity. Electrophoretic and densitometric scanning analysis of the aggregate phase of this mixture showed the fraction of Hb FS-fumarate to be 19%. Hb F-fumarate's effect on the delay time is concentration-dependent; the greater the concentration of Hb F-fumarate, the longer the delay time. The turbidity after aggregation of the mixture of Hb S and Hb F-fumarate was much less than that of Hb S and Hb FS-fumarate. However, the fraction of Hb F-fumarate in the aggregate phase was 19%, which is similar to that of Hb FS-fumarate. These data suggest that Hb F and FS hybrid hemoglobin cannot participate in nuclei formation, but can participate in aggregation after sufficient amounts of nuclei are formed from Hb S, and that increased levels of Hb F do not have an inhibitory effect on the formation of nuclei but on the growth of aggregates.     

Hemoglobin Fort Gordon or alpha2beta2145 Tyr replaced by Asp, a new high-oxygen-affinity hemoglobin variant.

Hemoglobin Fort Gordon, alpha2beta2145 Tyr replaced by Asp (HC2), has been observed in a 20-year-old black male with compensatory erythrocytosis. The variant was readily identified by electrophoresis and chromatography, and comprised about 30% of the red cell hemoglobin. The substitution was identified through analyses of tryptic peptides of various digests of the isolated beta chain. The oxygen affinity of whole blood was increased; two components were observed one of which had a greatly increased affinity for oxygen and a markedly reduced subunit cooperativity. It appears that the Tyr replaced by Asp substitution resembles the Tyr replaced by His substitution in hemoglobin Bethesda (Bunn, H. F. et al. (1972) J. Clin. Invest. 51, 2299-2309; Olson, J. S. and Gibson, G. H. (1972) J Biol. Chem. 247, 3662-3670; Adamson et al. (1972) J. Clin. Invest. 51, 2883-2888) in that both inhibit the quarternary change of the oxy to the deoxy conformation, resulting in greatly altered functional properties. Studies of a few members of the family were negative.     

First case of a single heterozygote of an abnormal hemoglobin,Hb Stanmore, [beta111(G13)Val-->Ala

We describe a hemoglobin beta-chain mutant detected incidentally in an unusual profile of glycated hemoglobin (HbA1c) measured by ion-exchange HPLC. Analysis of intact globin by electrospray ionization mass spectrometry (ESI-MS) and peptide analysis by on-line HPLC-ESI-MS-MS revealed the substitution, [beta111(G13)Val-->Ala], which was confirmed by DNA analysis. This was the second case of Hb Stanmore. As the first case combined beta(0)-thalassemia, and the family study in that case showed no case of Hb Stanmore without combined thalassemia, the case presented here is the first case of single heterozygote, and the first Japanese case. Hb Stanmore is isoelectrophoretically silent with only mild clinical symptoms, although stability by isopropanol test was positive.     

Hemoglobin Roseau-Pointe a Pitre alpha 2 beta 2(90) (F6) Glu----Gly: a new hemoglobin variant with slight instability and low oxygen affinity

A Dominican neonate carrying a new abnormal hemoglobin, hemoglobin Roseau Pointe-à-Pitre alpha 2 beta 2(90)(F6) Glu----Gly, was detected in Guadeloupe during application of a cord blood screening program. This variant behaved in isoelectrofocusing as an Hb D, and displayed instability and low whole blood oxygen affinity. In the affected family it was present, either isolated, or in association with a beta+ thalassemia trait.     

The Hb A variant (beta73 Asp-->Leu) disrupts Hb S polymerization by a novel mechanism

Polymerization of a 1:1 mixture of hemoglobin S (Hb S) and the artificial mutant HbAbeta73Leu produces a dramatic morphological change in the polymer domains in 1.0 M phosphate buffer that are a characteristic feature of polymer formation. Instead of feathery domains with quasi 2-fold symmetry that characterize polymerization of Hb S and all previously known mixtures such as Hb A/S and Hb F/S mixtures, these domains are compact structures of quasi-spherical symmetry. Solubility of Hb S/Abeta73Leu mixtures was similar to that of Hb S/F mixtures. Kinetics of polymerization indicated that homogeneous nucleation rates of Hb S/Abeta73Leu mixtures were the same as those of Hb S/F mixtures, while exponential polymer growth (B) of Hb S/Abeta73Leu mixtures were about three times slower than those of Hb S/F mixtures. Differential interference contrast (DIC) image analysis also showed that fibers in the mixture appear to elongate between three and five times more slowly than in equivalent Hb S/F mixtures by direct measurements of exponential growth of mass of polymer in a domain. We propose that these results of Hb S/Abeta73Leu mixtures arise from a non-productive binding of the hybrid species of this mixture to the end of the growing polymer. This "cap" prohibits growth of polymers, but by nature is temporary, so that the net effect is a lowered growth rate of polymers. Such a cap is consistent with known features of the structure of the Hb S polymer. Domains would be more spherulitic because slower growth provides more opportunity for fiber bending to spread domains from their initial 2-fold symmetry. Moreover, since monomer depletion proceeds more slowly in this mixture, more homogeneous nucleation events occur, and the resulting gel has a far more granular character than normally seen in mixtures of non-polymerizing hemoglobins with Hb S. This mixture is likely to be less stiff than polymerized mixtures of other hybrids such as Hb S with HbF, potentially providing a novel approach to therapy.     

Hb J-Antakya or alpha 2 beta (2)65(E9)Lys----Met in a Turkish family and Hb complutense or alpha 2 beta (2)127(H5)Gln----Glu in a Spanish family; correction of a previously published identification

Almost 10 years ago we reported in this journal the characterization of Hb Hacettepe or alpha 2 beta (2)127(H5)Gln----Glu. Unfortunately, we have to conclude that the original characterization of this Turkish variant was in error. The corrected data are presented in this short communication. The variant (alpha 2 beta (2)65(E9)Lys----Met) was (re)named Hb J-Antakya, after the city where the family resides. An abnormal Hb, observed in a Spanish family and named Hb Complutense, had the beta 127 Gln----Glu substitution, erroneously assigned to the Turkish variant.     

Stable octameric structure of recombinant hemoglobin alpha(2)beta(2)83 Gly-->Cys

We have engineered a recombinant hemoglobin (rHb betaG83C) based on the variant Hb Ta-Li, which oligomerizes through intertetramer disulfide bonds. Size exclusion chromatography and electrospray ionization mass spectrometry show that the rHb betaG83C assembles into an oligomeric structure the size of a dimer of tetramers. The oligomer has carbon monoxide-binding properties similar to those of natural human hemoglobin. Unlike HbA, the oligomer does not participate in dimer exchange. The CO kinetics, auto-oxidation rate, and gel filtration experiments on the oligomeric betaG83C did not show the usual concentration dependence, implying that it does not dissociate easily into smaller species. The octamer could be dissociated by the use of reducing agents. The action of reduced glutathione on oligomeric betaG83C exhibited biphasic kinetics for the loss of the octameric form, with a time constant for the rapid phase of about 2 h at 1 mM glutathione. However, the size of oligomer betaG83C was not modified after incubation with fresh plasma.     

Hemoglobin Izu (Macaca): beta83 (EF 7) Gly leads to Cys. A new hemoglobin variant found in the Japanese monkey (Macaca fuscata).

Recently, Ishimoto, Kuwata and Shotake reported a polymerizing hemoglobin found in Japanese monkey (Macaca fuscata) (J. Anthropol. Soc. Nippon 83, 233-243 (1975)). They separated the variant hemoglobin by gel filtration and from finger print results and from the fact that beta-mercaptoethanol dissociates the polymer deduced the substitution of an amino acid(s) by cysteine in the betaT10 peptide. We have purified the variant hemoglobin by ion-exchange chromatography using carboxymethyl cellulose after the protection of the reactive thiol groups with cystamine, and purified the betaT10 peptide and demonstrated that the usual glycine at beta 83 (EF 7) is substituted in the variant hemoglobin by cysteine.