CHARACTERIZATION OF THE CHICKEN TELOKIN HETEROGENEITY BY TIME-OF-FLIGHT MASS-SPECTROMETRY

Chicken gizzard telokin was purified to apparent homogeneity by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This preparation yielded upon mass spectrometry analysis seven mass peaks spanning from 15 858 to 17 100 Da, Anion exchange-high performance liquid chromatog raphy of the purified telokin revealed a high diversity of telokin mol ecules. By combining protein chemistry to chromatography and mass spec trometry, the telokin heterogeneity was analyzed. Three acetylated N-t ermini were found, AMI, MIS, and SGR. Cyanogen bromide cleavage of tel okin yielded six different C-terminal peptides corresponding to the re moval of one to six C-terminal glutamyl residues from the protein sequ ence deduced from the cDNA, Phosphorylation of telokin was detected, t hus increasing the heterogeneity of the telokin preparation. In additi on, peptide sequencing has shown that telokin contained either an aspa rtyl or a glutamyl residue at position 27, probably resulting from chi cken polymorphism.