Two new hemoglobin variants with deletion

“…Chain electrophoresis was carried out in urea-mercaptoethanol (Schneider, 1974b) and after dissociation with PCMB by the procedure of Bucci and Fronticelli (1965). The proportion of Hb F was determined by the alkali denaturation method of Betke et al (1959) and the heat stability test was performed according to Wajcman et al (1973).…”

Section: Methodsmentioning

confidence: 99%

Hemoglobin vancouver [α2β2 73(E17) Asp→ Tyr]: Its structure and function

et al. 1976

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Hemoglobin Vancouver is a new abnormal hemoglobin with an amino acid substitution of the normal aspartyl residue 73 of the beta chain by a tyrosyl residue. It was discovered in a man of Chinese descent in association with beta thalassemia. It was subsequently detected in a sister in association with normal Hb A. The oxygen affinity of the abnormal hemoglobin is decreased but its subunit interaction is normal. The Bohr effect may be slightly increased. This is the fourth abnormal hemoglobin to be found with a substitution at beta73. The others are Hb C-Harlem (alpha2beta2 6Glu replaced by Val and 73 Asp replaced by Asn), Hb Korle-Bu (alpha2beta2 73Asp replaced by Asn), and Hb Mobile (alpha2beta2 73Asp replaced by Val). Although Hb Mobile was found in the present studies to have a decreased affinity for oxygen, Hbs C-Harlem and Korle-Bu have been reported to be normal. These observations of functional differences for variants of beta73 added to earlier observations of the role of the normal beta73 residue to the aggregation of sickle deoxyhemoglobin indicate that this position of the molecule may be important in intra as well as intermolecular interactions.

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“…Although chains elongated at the carboxyl terminus have been described (14)(15)(16)(17), Hb-Grady is the first example of elongation by insertion of residues somewhere between the termini. Seven variants are known in which one to five residues are deleted (18)(19)(20)(21)(22)(23). Such a deletion might arise by a simple loss of base pairs from a chromosome or chromatid or it might arise by intragenic unequal crossing-over involving two chromatids.…”

Section: Discussionmentioning

confidence: 99%

Hemoglobin Grady: The First Example of a Variant with Elongated Chains Due to an Insertion of Residues

Huisman

Wilson

Gravely

et al. 1974

Proc. Natl. Acad. Sci. U.S.A.

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A black 25-year-old woman and her father have a fast-moving a chain variant in an amount of 8% (the father) and 18% (the daughter). Structural data indicate that this chain has been elongated by the addition of three amino-acid residues to give the sequence: -Pro-(114)-Ala(115)-Glu(116)-Phe(117)-Thr(118)-Glu-Phe-ThrPro(119)-Ala(120)-. The underlying genetic alteration responsible for hemoglobin Grady appears, therefore, to be a tandem duplication of nine base pairs which may have arisen by a process of mismatched intragenic crossing over. Functional and physicochemical properties of the variant are not greatly altered, and hematological data are normal.Comparative phylogenetic studies of sequences of many proteins suggest that intragenic duplications have played an important role in the evolution of structural genes and proteins. The evidence for such duplications has been reviewed elsewhere (1). We report here the first case of tandem repetition of a short sequence of amino-acid residues occurring in the a chain of a human hemoglobin (Hb). The variant, termed Hb-Grady, was observed in a 25-year-old black woman and her father. It has an increased electrophoretic mobility at alkaline pH, and subsequent structural analyses showed that its a chains were elongated with three amino-acid residues because the sequence Glu-Phe-Thr in positions 116-118 was repeated. Since this variant has been detected thus far in only two members of one family, it may be assumed that the tandem intragenic duplication is of recent origin. The nature of the duplication is such as to suggest that it may have arisen by unequal crossing-over. EXPERIMENTALSource of Blood. Samples from the propositus and from five relatives were collected in EDTA and analyzed in Atlanta or shipped by air to Augusta, Ga.Identification Procedures. Solutions of Hb were prepared by mixing one volume of washed erythrocytes with one volume of distilled water and 0.5 volume of carbontetrachloride. Debris was removed by centrifugation. Initial identification of the Hb types was made by cellulose acetate electrophoresis in Tris-EDTA-borate buffer (pH 8.4) (2), and by starch gel electrophoresis with the Tris-EDTA-borate discontinuous buffer system, pH 9.0 (3). Alkali-resistant Hb was measured by the method of Betke et al. (4). Chromatographic analyses made use of columns of DEAE-Sephadex (5, 6) or DEAEcellulose (7).Isolation of Hb Variant and Abnormal Chain. The variant was isolated bv chromatography on DEAE-Sephadex (5, 6). Hb-Grady was contaminated with the normally occurring minor Hb-A1, but was used without further purification because the abnormal a chain of Hb-Grady was readily separated from the the normal a chain of Hb-A1 on 1.7 X 15-cm columns of carboxymethylcellulose (8).Digestion of the a Chain. The chain was digested with trypsin for 4 hr at room temperature in a pH stat at pH 9.0 with addition of enzyme at zero and at 1 hr in an enzyme: protein ratio of 1: 100. The pH was lowered to 6.5, and the insoluble core was isolated by centrifugation. The pH...

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Two new hemoglobin variants with deletion

Cited by 44 publications

References 27 publications

Aspects of Molecular Evolution

Aspects of Molecular Evolution

Hemoglobin vancouver [α2β2 73(E17) Asp→ Tyr]: Its structure and function

Hemoglobin Grady: The First Example of a Variant with Elongated Chains Due to an Insertion of Residues

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