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：5
页码：2338-2342
DOI：10.1073/pnas.75.5.2338
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：mRNA from rat mammary glands 13-15 days post partum was translated in a wheat germ cell-free system either in the absence or in the presence of ribosome-denuded membranes prepared from isolated rough microsomes of dog pancreas. Newly synthesized -lactalbumin was identified by immunoprecipitation with a monospecific rabbit antiserum against rat -lactalbumin and was characterized by partial amino-terminal sequence determination and by lectin affinity chromatography. In the absence of membranes a presumably unglycosylated form of -lactalbumin was synthesized that bound neither to concanavalin A-Sepharose nor to Ricinus communis lectin-agarose and that contained an amino-terminal signal peptide region comprising 19 amino acid residues. In the presence of membranes a processed form was synthesized that lacked the signal peptide portion and that had an amino-terminal sequence identical to that of mature -lactalbumin. Furthermore, this processed form was found to be segregated, presumably within the microsomal vesicles, because it was resistant to post-translational proteolysis. It was also found to be glycosylated, and because it bound to concanavalin A-Sepharose, from which it could be eluted specifically by -methyl mannoside, but not to R. communis lectin-agarose, it was presumably core-glycosylated. Processing, segregation, and core glycosylation were observed to proceed only when membranes were present during translation and not when they were added after translation.
关键词：rat mammary mRNA ; immunoprecipitation of α-lactalbumin ; dog pancreas microsomal membranes ; lectin chromatography ; radiosequencing
