Topology of eukaryotic type II membrane proteins: importance of N-terminal positively charged residues flanking the hydrophobic domain.
We have tested the role of different charged residues flanking the sides of the signal/anchor (S/A) domain of a eukaryotic type II (N(cyt)C(exo)) integral membrane protein in determining its topology. The removal of positively charged residues on the N-terminal side of the S/A yields proteins with an inverted topology, while the addition of positively charged residues to only the C-terminal side has very little effect on orientation. Expression of chimeric proteins composed of domains from a type II protein (HN) and the oppositely oriented membrane protein M2 indicates that the HN N-terminal domain is sufficient to confer a type II topology and that the M2 N-terminal ectodomain can direct a type II topology when modified by adding positively charged residues. These data suggest that eukaryotic membrane protein topology is governed by the presence or absence of an N-terminal signal for retention in the cytoplasm that is composed in part of positive charges.
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Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, Illinois 60208-3500.
Lamb
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D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D004279:DNA, Viral / Q000235:genetics; D006031:Glycosylation; D015707:HN Protein / Q000235:genetics* / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D008861:Microsomes / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010957:Plasmids; D011487:Protein Conformation; D012190:Retroviridae / Q000235:genetics*; D014162:Transfection; D014616:Vaccinia virus / Q000235:genetics
D004279:DNA, Viral; D015707:HN Protein; D008562:Membrane Glycoproteins