title: Amino-terminal basic residues of Src mediate membrane binding through electrostatic interaction with acidic phospholipids.
abstract: Membrane targeting of pp60src (Src) is mediated by its myristoylated amino terminus. We demonstrate that, in addition to myristate, six basic residues in the amino terminus are essential for high-affinity binding to the lipid bilayer via electrostatic interaction with acidic phospholipids. Specifically, c-Src was shown to bind 2500-fold more strongly to vesicles composed of the physiological ratio of 2:1 phosphatidylcholine (PC)/phosphatidylserine (PS) than to neutral PC bilayer vesicles. The apparent Kd for binding of c-Src to the PC/PS bilayer was 6 x 10(-7) M. This interaction is sufficiently strong to account for c-Src membrane targeting. Mutants of c-Src in which the amino-terminal basic residues were replaced by neutral asparagine residues exhibited binding isotherms approaching that of wild-type binding to neutral bilayers (apparent Kd of 2 x 10(-3) M). The transforming v-Src and activated c-Src (Y527F) proteins also bound more strongly to PC/PS bilayers (apparent Kd of approximately 1 x 10(-5) M) than to neutral PC bilayers. In vivo experiments with Src mutants confirmed the role of positive charge in mediating membrane binding and cellular transformation.
authors.affiliation: Cell Biology and Genetics Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10021.
authors.forename: C T
authors.initials: CT
authors.lastname: Sigal
authors.forename: W
authors.initials: W
authors.lastname: Zhou
authors.forename: C A
authors.initials: CA
authors.lastname: Buser
authors.forename: S
authors.initials: S
authors.lastname: McLaughlin
authors.forename: M D
authors.initials: MD
authors.lastname: Resh
mesh_terms: D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D004563:Electrochemistry; D007700:Kinetics; D008051:Lipid Bilayers; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009842:Oligopeptides / Q000138:chemical synthesis / Q000494:pharmacology; D015688:Oncogene Protein pp60(v-src) / Q000737:chemistry* / Q000378:metabolism*; D010743:Phospholipids / Q000737:chemistry / Q000378:metabolism*; D017354:Point Mutation; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013329:Structure-Activity Relationship; D014162:Transfection
chemical_list: D008051:Lipid Bilayers; D009842:Oligopeptides; D010743:Phospholipids; D011994:Recombinant Proteins; D015688:Oncogene Protein pp60(v-src); D016392:Proto-Oncogene Proteins pp60(c-src)