Separation of the tryptic peptides and cyanogen bromide fragments of the human embryonic zeta chains of hemoglobin in Portland I and II by reverse phase high performance liquid chromatography.

Abstract

The amino acid compositions of tryptic peptides and cyanogen bromide fragments of the purified zeta chain of Hb Portland I (zeta 2 gamma 2) and Hb Portland II (zeta 2 beta 2) have been determined. The hemoglobins were obtained from blood from neonates with hydrops fetalis due to homozygous alpha-thalassemia. The globin chains, tryptic peptides and cyanogen bromide fragments were all separated by reverse phase high performance liquid chromatography (HPLC). Several different types of C-18 columns were used with two different developer systems. The tryptic peptides of aminoethylated zeta chain were separated using an ammonium acetate-acetonitrile gradient. An aqueous trifuoroacetic acid-1-propanol developer gradient was used for the separation of cyanogen bromide fragments. Of the seventeen tryptic peptides obtained, two (zeta T10a and zeta T10b) resulted from the unusual cleavage of a Tyr-Ile peptide bond. This was observed even when using TPCK treated trypsin. From this study and results of others, it can be deduced that trypsin will hydrolyze the Tyr-X bond provided either Ala or Ile is bonded to the N-terminal side of Tyr and Ile, Leu, or Gly is bonded to the C-terminal side of the Tyr residue.