Processing at the carboxyl terminus of nascent placental alkaline phosphatase in a cell-free system: evidence for specific cleavage of a signal peptide.
Alkaline phosphatase is anchored to the plasma membrane by a carboxyl-terminal phosphatidylinositol glycan moiety. To investigate the biosynthesis of mature alkaline phosphatase, nascent human placental alkaline phosphatase was expressed in a cell-free system and used as substrate for in vitro processing by microsomal extracts. By monitoring the processed product with three site-directed antibodies, it was shown that microsomal extracts from CHO cells that contain other recognized processing activities also remove the carboxyl-terminal signal peptide from the preproenzyme in an apparently selective manner. This peptidase-like cleavage may be brought about by the action of a specific transamidase acting on the nascent protein in the absence of an appropriate phosphatidylinositol glycan cosubstrate.
Bailey
C A
CA
Roche Institute of Molecular Biology, Nutley, NJ 07110.
Gerber
L
L
Howard
A D
AD
Udenfriend
S
S
D000469:Alkaline Phosphatase / Q000235:genetics*; D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000201:enzymology; D002474:Cell-Free System; D005260:Female; D006801:Humans; D007425:Intracellular Membranes / Q000201:enzymology; D007700:Kinetics; D008861:Microsomes / Q000201:enzymology; D010920:Placenta / Q000201:enzymology*; D011247:Pregnancy; D011499:Protein Processing, Post-Translational; D021382:Protein Sorting Signals / Q000378:metabolism*; D011817:Rabbits; D012156:Reticulocytes / Q000378:metabolism
D021382:Protein Sorting Signals; D000469:Alkaline Phosphatase