期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1978
卷号：75
期号：2
页码：715-719
DOI：10.1073/pnas.75.2.715
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Translation in vitro of the mRNA coding for the vesicular stomatitis virus membrane glycoprotein G in a membrane-free ribosomal extract from HeLa cells allowed the synthesis of only the unglycosylated protein G1 (molecular weight, 63,000). Addition of stripped crude microsomal membranes from HeLa cells resulted in the conversion of G1 to the glycosylated protein G2 (molecular weight, 67,000). The G2 protein synthesized by the reconstructed microsomal membrane/ribosome system was found to be segregated inside the microsomal membrane vesicles and was thus protected from the proteolytic action of trypsin and chymotrypsin. Stripped membranes were required at an early stage of protein synthesis for the synthesized protein to be inserted into the membrane vesicles and to be glycosilated. The segregated protein G2, however, was not completely protected from proteolytic digestion, showing that a portion of the polypeptide chain of about 3000 daltons was present on the cytoplasmic side of the membrane vesicle. Our data thus suggest that, unlike the secretory proteins, the membrane glycoproteins are not completely discharged across the microsomal membranes.
