A membrane-anchored form but not the secretory form of human chorionic gonadotropin-alpha chain acquires polylactosaminoglycan - PubMed (original) (raw)

. 1988 Apr 15;263(11):5314-8.

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A membrane-anchored form but not the secretory form of human chorionic gonadotropin-alpha chain acquires polylactosaminoglycan

M Fukuda et al. J Biol Chem. 1988.

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Abstract

Large polylactosaminoglycans have only been observed linked to membrane proteins. To determine if membrane anchoring of a secretory protein might lead to the addition of polylactosaminoglycan, we have examined the carbohydrate structure on a membrane-anchored form of human chorionic gonadotropin-alpha subunit. This protein was generated by fusing the DNA encoding the human chorionic gonadotropin-alpha subunit to the DNA encoding the membrane-spanning and cytoplasmic domains of the vesicular stomatitis virus glycoprotein. DNAs encoding this hybrid form and the secretory form of human chorionic gonadotropin-alpha were expressed in monkey COS-1 cells using an SV40-based vector. We show here that the parent secretory glycoprotein contains typical Asn-linked complex-type oligosaccharides while the membrane-bound form contains large, heterogenous polylactosaminoglycans. We conclude that membrane anchoring increases the accessibility of the N-linked glycans to the enzymes involved in polylactosamine addition. The inhibitor 1-deoxymannojirimycin blocks addition of the polylactosaminoglycan.

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