Fine-tuning the topology of a polytopic membrane protein: role of positively and negatively charged amino acids.
The effects of positively and negatively charged residues on the membrane topology of a model E. coli protein with two transmembrane segments have been studied. We show that addition or removal of as little as a single positively charged lysine residue in one of two critical regions can be sufficient to reverse the transmembrane topology of the molecule from Nout-Cout to Nin-Cin. Negatively charged residues are much less potent and significantly affect the topology only if present in high numbers. Finally, we provide data to suggest that sec-independent and sec-dependent translocation mechanisms differ in their sensitivity to positively charged amino acids.
Nilsson
I
I
Department of Molecular Biology, Karolinska Institute Center for Biotechnology, NOVUM, Huddinge, Sweden.
von Heijne
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G
D000595:Amino Acid Sequence; D000599:Amino Acids, Diamino; D000600:Amino Acids, Dicarboxylic; D002462:Cell Membrane / Q000502:physiology* / Q000648:ultrastructure; D010450:Endopeptidases / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics / Q000648:ultrastructure; D008239:Lysine; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure*; D008969:Molecular Sequence Data; D009154:Mutation; D010957:Plasmids; D011487:Protein Conformation; D012697:Serine Endopeptidases
D000599:Amino Acids, Diamino; D000600:Amino Acids, Dicarboxylic; D008565:Membrane Proteins; D010450:Endopeptidases; D012697:Serine Endopeptidases; C026515:type I signal peptidase; D008239:Lysine