Topogenic signals in integral membrane proteins.
Integral membrane proteins are characterized by long apolar segments that cross the lipid bilayer. Polar domains flanking these apolar segments have a more balanced amino acid composition, typical for soluble proteins. We show that the apolar segments from three different kinds of membrane-assembly signals do not differ significantly in amino acid content, but that the inside/outside location of the polar domains correlates strongly with their content of arginyl and lysyl residues, not only for bacterial inner-membrane proteins, but also for eukaryotic.proteins from the endoplasmic reticulum, the plasma membrane, the inner mitochondrial membrane, and the chloroplast thylakoid membrane. A positive-inside rule thus seems to apply universally to all integral membrane proteins, with apolar regions targeting for membrane integration and charged residues providing the topological information.
D000596:Amino Acids / Q000032:analysis*; D001120:Arginine / Q000032:analysis; D005057:Eukaryotic Cells / Q000032:analysis; D008051:Lipid Bilayers; D008239:Lysine / Q000032:analysis; D008565:Membrane Proteins / Q000032:analysis*; D011387:Prokaryotic Cells / Q000032:analysis
D000596:Amino Acids; D008051:Lipid Bilayers; D008565:Membrane Proteins; D001120:Arginine; D008239:Lysine