Studies on Human Serum Albumin

Human serum albumin (HSA) is very similar to BSA in physical properties (Foster, 1960) and also in the N-F transition near pH 4 (Clark et al., 1962). Therefore, most of the information discussed in Sections I and II will also pertain to HSA. The amino acid sequence of HSA has recently been established (Behrens et al., 1975 Meloun et al., 1975) and shows that the three-domain feature that prevailed in BSA is also evident in the structure of HSA (Fig. 23). However, there were some differences between the data of the two groups. Sequences reported by Meloun et al (1975) included phenylalanine at position 157, which was deleted in the original sequence of Behrens et al. (1975). However, the latter group (Behrens, private communication, 1977) included a phenylalanine at position 157. Other differences occurred in the assignment of acid/amide states of the acidic amino acids and also in the identity of residues at 16 positions. 

It is not apparent whether the differences in the sequence of HSA reported by the two groups were the outcome of microheterogeneity, which was often demonstrated, or whether they were due to experimental errors. At the moment, the only strong evidence for microheterogeneity of albumin as a result of the primary structure comes from the work by Lapresle and Doyen (1975), who showed, by cyanogen bromide cleavage of HSA, that about 16% of the molecules lacked methionine at position 123. 

The effect of chemical modification on the immunochemical reactivity, data for which ane very limited. 

Isolation of immunochemically reactive peptides. A good deal of progress has resulted from this approach. 

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