The tryptic peptide composition of the beta chains of hemoglobins A and B of the domestic cat (Felis catus)

Summary

The tryptic peptides from theβ ^A andβ ^B chains of cat hemoglobins A and B have been isolated and the amino acid compositions determined. Differences between the two chains were found in two peptides,βT-1 (Gly→Ser) andβT-14 (Asn→Ser and Lys→Arg). The Gly→Ser and Lys→Arg substitutions are placed atβ-1 andβ-144 respectively from earlier work, and the third substitution, Asn→Ser atβ-139 is suggested from this work. In addition, the presence of a blocked amino terminus inβ ^B has been confirmed. Tentative sequences constructed by homology with knownβ-chain structures suggest the occurrence of substitutions atα ₁ β ₁ contacts inβ ^A andβ ^B that may be functionally significant. There are at least 18 differences in amino acid composition between catβ ^A and dogβ-chains and 22 differences between catβ ^A and normal adult humanβ-chains.