title: Anomalies in the translocation and processing of glycophorin precursors in murine erythroleukemia cells.
abstract: Analogues of human glycophorins have been identified in many species, including mouse. In murine erythroleukemia cells three mature glycophorins (gp-2, gp-3, 34K) and four putative precursors (21K, 23K, 26K, and 27K) are expressed. Pulse-chase labeling experiments suggest that 21K and 23K are the precursors of the gp-3 doublet of proteins 29K and 30K. Precursor-product relationships were not found for 26K, 27K, 34K, and gp-2. Two experimental approaches, i.e. cell-free translation and subcellular distribution, have identified processing anomalies in the glycophorins. First, signal sequences, if present, are apparently not cleaved upon translocation across the endoplasmic reticulum membrane; second, the 26K and 27K putative precursors are inefficiently translocated. The majority accumulates in the cytosol or associates with the endoplasmic reticulum membrane without acquiring protection against V8 protease. Only a minority (approximately 10%) is properly translocated.
authors.affiliation: Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06510.
authors.forename: J B
authors.initials: JB
authors.lastname: Ulmer
authors.forename: G E
authors.initials: GE
authors.lastname: Palade
mesh_terms: D000818:Animals; D002460:Cell Line; D002999:Clone Cells; D006021:Glycophorins / Q000096:biosynthesis / Q000235:genetics*; D006801:Humans; D007700:Kinetics; D004915:Leukemia, Erythroblastic, Acute; D051379:Mice; D008970:Molecular Weight; D010449:Peptide Mapping; D014176:Protein Biosynthesis; D011499:Protein Processing, Post-Translational; D012333:RNA, Messenger / Q000235:genetics; D012795:Sialoglycoproteins / Q000235:genetics*; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: D006021:Glycophorins; D012333:RNA, Messenger; D012795:Sialoglycoproteins