Cleavage without anchor addition accompanies the processing of a nascent protein to its glycosylphosphatidylinositol-anchored form.
Rough microsomal membranes from most mammalian cells, in the presence of a translation system, process nascent proteins with appropriate COOH-terminal signal peptides to their mature glycosylphosphatidylinositol (GPI)-linked forms. The present study, using preprominiplacental alkaline phosphatase as substrate, shows that as much as 10% of the mature product is cleaved correctly but is not linked to GPI. Some of the factors that influence the relative proportions of GPI linked to free mini-placental alkaline phosphatase are the amounts of GPI in the cells and the amino acid substituent at the omega site of the nascent protein. A mechanism for explaining cleavage both with and without GPI addition is presented, which supports a transamidase type of enzyme as the catalyst.
Maxwell
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Roche Institute of Molecular Biology, Roche Research Center, Nutley, NJ 07110-1199.
Ramalingam
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Gerber
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LD
Udenfriend
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D000469:Alkaline Phosphatase / Q000378:metabolism*; D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D017261:Glycosylphosphatidylinositols / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D066298:In Vitro Techniques; D008861:Microsomes / Q000378:metabolism; D008970:Molecular Weight; D010920:Placenta / Q000201:enzymology; D014176:Protein Biosynthesis; D011499:Protein Processing, Post-Translational; D011506:Proteins / Q000378:metabolism*
D017261:Glycosylphosphatidylinositols; D011506:Proteins; C055324:phospholipase A2-activating protein; D000469:Alkaline Phosphatase