W. Chen et al., COTRANSLATIONAL FOLDING AND CALNEXIN BINDING DURING GLYCOPROTEIN-SYNTHESIS, Proceedings of the National Academy of Sciences of the United Statesof America, 92(14), 1995, pp. 6229-6233
To analyze cotranslational folding of influenza hemagglutinin in the e
ndoplasmic reticulum of live cells, we used short pulses of radiolabel
ing followed by immunoprecipitation and analysis with a two-dimensiona
l SDS/polyacrylamide gel system which was nonreducing in the first dim
ension and reducing in the second, It separated nascent glycopolypepti
des of different length and oxidation state. Evidence was obtained for
cotranslational disulfide formation, generation of conformational epi
topes, N-linked glycosylation, and oligosaccharide-dependent binding o
f calnexin, a membrane-bound chaperone that binds to incompletely fold
ed glycoproteins via partially glucose-trimmed oligosaccharides, When
glycosylation or oligosaccharide trimming was inhibited, the folding p
athway was perturbed, suggesting a role for N-linked oligosaccharides
and calnexin during translation of hemagglutinin.