Structures of the carbohydrate moiety of ovalbumin glycopeptide III and the difference in specificity of endo-beta-N-acetylglucosaminidases CII and H

Investigation by 360-MHz 1H-nuclear-magnetic-resonance spectroscopy and methylation analysis of the single glycan chain of chicken ovotransferrin

The primary structure of two glycopeptides obtained by pronase digestion of chicken ovotransferrin has been investigated by 360-MHz proton nuclear magnetic resonance (NMR) spectroscopy and methylation analysis. The two glycopeptides differ in amino acid composition but contain the same carbohydrate moiety, viz: (formula: see text). Using the NMR data of some reference compounds the chemical shifts of the anomeric protons and mannose H-2 protons could be predicted with an accuracy of 0.01 ppm.

Studies of the diphtheria toxin receptor on Chinese hamster cells

Concanavalin A, wheat germ agglutinin and the ovalbumin glycopeptide are all inhibitors of the cytotoxic effect of diphtheria toxin on Chinese hamster cells. Ovalbumin glycopeptide loses its inhibitory property after treatment with beta-N-acetylglucosaminidase. This demonstrates the importance of the glycopeptide structure for the mechanism of inhibition. The glycopeptide may be a toxin cell-surface receptor analogue. Diphtheria toxin-resistant mutants were isolated in order to search for cells that might have an altered toxin receptor. One mutant was 10- to 15-fold more resistant to diphtheria toxin than wild-type cells when protein synthesis was measured as a function of toxin concentration. However, when protein synthesis was measured as a function of time at a high toxin concentration, the time before onset of inhibition was identical in the mutant and wild-type cells. We present evidence indicating that the resistance of this mutant can be accounted for by a decreased affinity of toxin for a cell-surface receptor.