Co-and post-translational events in the biogenesis of pig small intestinal aminopeptidase N
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The biogenesis of pig small intestinal aminopeptidase N (EC 3. 4. 11. 2) was studied by cell-free translation of intestinal mRNA and by labelling of organ cultured intestinal explants. In cell-free translation, the primary mRNA translation product of aminopeptidase N was a polypeptide of Mr 115,000. When translation was performed in the presence of dog pancreatic microsomes, a Mr 140,000 polypeptide was also observed. A polypeptide of Mr 115,000 was seen for the enzyme, purified from tunicamycin exposed explants. This result suggests that aminopeptidase N is co-translationally inserted into the membrane without cleavage of the signal. Pulse-chase labelling of explants gave the following results: 1. Immediately after a 10 min pulse with [35S] methionine, aminopeptidase N was detected in the Ca2+-precipitated membrane fraction. 2. The earliest detectable form of the enzyme, a polypeptide of Mr 140,000, was "high mannose" glycosylated as judged by its sensitivity to endoglycosidase H. After 40 min of chase, a re-glycosylation, yielding the mature form of Mr 166,000, occurred. 3. Aminopeptidase N was expressed at the microvillar membrane after 60-90 min of chase. Monensin inhibited the conversion from high mannose to complex glycosylation and the appearance of the enzyme in the microvillar membrane, indicating a role of the Golgi complex in these processes. Colchicine prevented aminopeptidase N from reaching the microvillar membrane, suggesting the involvement of microtubules in the transport.
Original language | English |
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Journal | Tokai Journal of Experimental and Clinical Medicine |
Volume | 7 Suppl |
Pages (from-to) | 135-40 |
Number of pages | 5 |
ISSN | 0385-0005 |
Publication status | Published - 1982 |
Bibliographical note
Keywords: Aminopeptidases; Animals; Antigens, CD13; Cell Membrane; Electrophoresis, Polyacrylamide Gel; Intestine, Small; Molecular Weight; Protein Biosynthesis; Protein Processing, Post-Translational; RNA, Messenger; Swine
ID: 13063873