Characterization and localization of an iron-binding 18-kDa glycopeptide isolated from the N-terminal half of humanlactotransferrin

Abstract

Mild treatment of iron-saturated human lactotransferrin by trypsin at pH 8.2 cleaves the molecule into a N-tryptic ( M r ≈ 30 000) and a C-tryptic ( M r ≈ 50 000) fragment, which have been isolated. Each of them carries a glycan moiety and keeps the property to bind reversibly one Fe 3+. The N-tryptic fragment has been submitted to a second tryptic digestion which led to an iron-binding glycopeptide fragment with a molecular weight of about 18 500. This fragment, the smallest iron-binding peptide isolated up to now from a transferrin, includes the ND2 domain of human lactotransferrin.