title: Binding of prenylated and polybasic peptides to membranes: affinities and intervesicle exchange.
abstract: The small GTP-binding protein G25K and the protein K-Ras 4B contain prenyl groups (geranylgeranyl and farnesyl, respectively) that are thioether linked to a C-terminal cysteine which is methylated on its alpha-carboxyl group. These proteins, like many other prenyl proteins, also have a string of basic residues near their C-termini. A series of prenylated peptides based on the C-terminal sequences of human brain G25K and human K-Ras 4B were synthesized and analyzed for their membrane binding affinities. G25K peptides containing an N-terminal N-acetyltryptophan group were studied because their binding to membranes containing a trace of dansylated phospholipid could be detected by fluorescence resonance energy transfer. The G25K peptide lacking a prenyl group and a C-terminal methyl ester did not detectably bind to vesicles, and binding was enhanced by more than 500-fold if the peptide was geranylgeranylated. For the farnesylated peptide, methylation of the C-terminus increased membrane affinity by at least 60-fold if the vesicles contained phosphatidylserine and by 3-fold if they lacked this acidic lipid. The geranylgeranylated and methylated G25K peptide remains irreversibly attached to vesicles over several minutes only if the vesicles contain phosphatidylserine, whereas the corresponding nonmethylated or farnesylated and methylated peptides dissociate rapidly (less than a few seconds) from neutral or anionic vesicles. Farnesylation of the nonmethylated K-Ras 4B peptide enhances its affinity to vesicles containing acidic phospholipids (phosphatidylglycerol or phosphatidylserine) by 70-fold, and methylation leads to an additional dramatic (150-fold) increase in membrane affinity.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Chemistry, University of Washington, Seattle 98195, USA.
authors.forename: F
authors.initials: F
authors.lastname: Ghomashchi
authors.forename: X
authors.initials: X
authors.lastname: Zhang
authors.forename: L
authors.initials: L
authors.lastname: Liu
authors.forename: M H
authors.initials: MH
authors.lastname: Gelb
mesh_terms: D000595:Amino Acid Sequence; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D002942:Circular Dichroism; D004563:Electrochemistry; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D008081:Liposomes; D008567:Membranes, Artificial; D008969:Molecular Sequence Data; D015394:Molecular Structure; D010455:Peptides / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D017368:Protein Prenylation; D013816:Thermodynamics; D020764:cdc42 GTP-Binding Protein; D018631:ras Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D018797:Cell Cycle Proteins; D008081:Liposomes; D008567:Membranes, Artificial; D010455:Peptides; D019204:GTP-Binding Proteins; D020764:cdc42 GTP-Binding Protein; D018631:ras Proteins