| Abstract: |
Membrane association is required for cell transformation by pp60v-src (v-Src), the product of the v-src oncogene of Rous sarcoma virus. Previous experiments have identified two NH2-terminal membrane-binding motifs: a myristate (14-carbon acyl chain) attached to the NH2-terminal glycine and three basic residues at positions 5,7, and 9 of Src. We examined the membrane binding of each motif using myristylated (myr-src) and nonmyristylated (nonmyr-src) peptides corresponding to the NH2 terminus of Src. All myristylated peptides partitioned equally well onto electrically neutral phosphatidylcholine vesicles (K1 = 104 M−1). Identical binding has been observed for simple myristylated peptides (e.g., myr-Gly) and arises from the hydrophobic insertion of the myristate into the bilayer. A nonmyristylated peptide corresponding to residues 2-16 of Src [nonmyr-src(2-16), net charge = +5] bound to vesicles containing 33% monovalent acidic phospholipids with K1 = 103 M−1. Penta(lysine) (+5 net charge) exhibits the same binding behavior, which is due to the electrostatic interaction between basic residues and acidic lipids. The corresponding myristylated peptide, myr-src(2-16), binds 3 orders of magnitude more strongly to vesicles containing 33% acidic lipids than to neutral vesicles. The resulting apparent association constant, K1 = 107 M−1, is approximately equal to the product of the partition coefficients for the two individual interactions. This 107 M−1 binding is sufficiently strong to anchor the Src protein to biological membranes. We propose a simple model that explains the observed synergism between the two peptide-membrane interactions. © 1994, American Chemical Society. All rights reserved. |
| Keywords: |
protein binding; structure activity relation; amino acid sequence; molecular sequence data; amino terminal sequence; isotope labeling; models, molecular; amino acids; lipid bilayers; membrane binding; electrophoresis, polyacrylamide gel; gene expression regulation, viral; protein kinase p60; myristylation; coated vesicles; rous sarcoma virus; binding kinetics; oncogene protein pp60(v-src); priority journal; article; support, non-u.s. gov't; support, u.s. gov't, p.h.s.; support, u.s. gov't, non-p.h.s.; myristates; chimeric proteins; sarcoma viruses, avian
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