title: Interaction of wild-type signal sequences and their charged variants with model and natural membranes.
abstract: The interaction of synthetic peptides corresponding to wild-type signal sequences, and their mutants having charged amino acids in the hydrophobic region, with model and natural membranes has been studied. At high peptide concentrations, i.e. low lipid/peptide ratios, the signal peptides cause release of carboxyfluorescein (CF) from model membranes with lipid compositions corresponding to those of translocation-competent as well as translocation-incompetent membranes. Interestingly, mutant sequences, which were non-functional in vivo, caused considerable release of CF compared with the wild-type sequences. Both wild-type and mutant signal sequences perturb model membranes even at lipid/peptide ratios of 1000:1, as indicated by the activities of phospholipases A2, C and D. These studies indicate that such mutant signals are non-functional not because of their inability to interact with membranes, but due to defective targeting to the membrane. The signal peptides inhibit phospholipase C activity in microsomes, uncouple oxidative phosphorylation in mitochondria and increase K+ efflux from erythrocytes, and one of the mutant sequences is a potent degranulator of the mast cells. Both wild-type and mutant signal sequences have the ability to perturb vesicles of various lipid compositions. With respect to natural membranes, the peptides do not show any bias towards translocation-competent membranes.
authors.affiliation: Centre for Cellular and Molecular Biology, Hyderabad, India.
authors.forename: N M
authors.initials: NM
authors.lastname: Rao
authors.forename: R
authors.initials: R
authors.lastname: Nagaraj
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism*; D004912:Erythrocytes / Q000378:metabolism; D005452:Fluoresceins / Q000378:metabolism*; D008407:Mast Cells / Q000378:metabolism; D008567:Membranes, Artificial; D008862:Microsomes, Liver / Q000378:metabolism; D008930:Mitochondria, Liver / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D010739:Phospholipase D / Q000378:metabolism; D010741:Phospholipases A / Q000378:metabolism; D011188:Potassium / Q000097:blood; D021382:Protein Sorting Signals / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D010738:Type C Phospholipases / Q000378:metabolism
chemical_list: D005452:Fluoresceins; D008567:Membranes, Artificial; D021382:Protein Sorting Signals; C024098:6-carboxyfluorescein; D010741:Phospholipases A; D010738:Type C Phospholipases; D010739:Phospholipase D; D011188:Potassium