Haemoglobin lyon (β17–18 (A 14–15) Lys-Val → O)

The human alpha-globin gene. The protein products of the duplicated genes are identical

In order to determine whether any heterogeneity exists in the human alpha-globin chain, i.e. whether the products of the duplicated genes are identical, we have determined the total sequence of 14 alpha-globin chains: seven of these were abnormal, while six were normal chains from the same individuals, with one additional sample which consisted of the alpha chains from a normal control. In the individuals heterozygous for an alpha-chain abnormality, the product of a single alpha-gene could be isolated from that of the three others using the differing physicochemical properties of the mutant haemoglobins. In the special situation of a double heterozygosity for an alpha-chain abnormality, the products of the two mutated genes were separated from each other and from the mixture of the products of the two normal genes. They were then investigated independently, this approach increased the precision of our work. During the course of the present investigation, sequence determinations were mainly performed on large fragments of the chains, which were purified exclusively by gel chromatography. In this way mixtures of products of several genes could be studied, thereby overcoming the risk of losing peptides differing slightly in sequence. Such loss may often occur when using ion-exchange procedures to purify small peptides. Our results show the absence of any heterogeneity at the level of the gene products of the duplicated alpha loci. Thus the human alpha-globin chain has to be considered as homogeneous.

The chemical heterogeneity of human hemoglobin F. Direct evidence for the existence of three types of gamma chain, the G gamma I, A gamma I, and A gamma T chains

Direct evidence is presented for the existence of three types of gamma chain of human hemoglobin F. A modification of a CM-cellulose chromatographic method has allowed the incomplete separation of these gamma chains while high pressure liquid chromatography and fingerprint analyses of tryptic peptides of zones of the isolated gamma chains, and amino acid analyses of isolated peptides were used to identify the chains. These studies have shown that the presence of a glycyl residue in position 136 (G gamma chain) is directly related to that of an isoleucyl residue in position 75 (I gamma chain), thus indicating the existence of an G gamma I chain, and that the presence of an alanyl residue in position 136 (A gamma chain) can be related to that of an isoleucyl residue in position 75, thus suggesting the existence of an A gamma I chain. When the isoleucyl residue at positive 75 is replaced by a threonyl residue, invariably it is related to the alanyl substitution at position 136 (A gamma T chain). These data support indirect evidence from case analyses and family studies which were published before, and indicate that the T gamma chain is an allele of the A gamma which should be renamed the A gamma T chain.

Haemoglobin Saki alpha 2 beta 2 14 Leu-Pro(a11) structure and function

The characterization of haemoglobin Saki alpha 2 beta 2 14 Leu-Pro(a11) is described. This new mutation is unique since it only induces modification of the stability of the molecule. In vitro precipitation of haemoglobin Saki upon heat or in the presence of chemicals is compared to the stability of haemoglobin A and haemoglobin S.