title: Tuning the insertion properties of pHLIP.
abstract: The pH (low) insertion peptide (pHLIP) has exceptional characteristics: at neutral pH it is an unstructured monomer in solution or when bound to lipid bilayer surfaces, and it inserts across a lipid bilayer as a monomeric alpha-helix at acidic pH. The peptide targets acidic tissues in vivo and may be useful in cancer biology for delivery of imaging or therapeutic molecules to acidic tumors. To find ways to vary its useful properties, we have designed and analyzed pHLIP sequence variants. We find that each of the Asp residues in the transmembrane segment is critical for solubility and pH-dependent membrane insertion of the peptide. Changing both of the Asp residues in the transmembrane segment to Glu, inserting an additional Asp into the transmembrane segment, or replacing either of the Asp residues with Ala leads to aggregation and/or loss of pH-dependent membrane insertion of the peptide. However, variants with either of the Asp residues changed to Glu remained soluble in an aqueous environment and inserted into the membrane at acidic pH with a higher pK(app) of membrane insertion.
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8114, USA.
authors.forename: Monika
authors.initials: M
authors.lastname: Musial-Siwek
authors.forename: Alexander
authors.initials: A
authors.lastname: Karabadzhak
authors.forename: Oleg A
authors.initials: OA
authors.lastname: Andreev
authors.forename: Yana K
authors.initials: YK
authors.lastname: Reshetnyak
authors.forename: Donald M
authors.initials: DM
authors.lastname: Engelman
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000737:chemistry*; D016503:Drug Delivery Systems; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008565:Membrane Proteins / Q000737:chemistry* / Q000494:pharmacology; D009369:Neoplasms / Q000188:drug therapy / Q000473:pathology; D017433:Protein Structure, Secondary
chemical_list: D008565:Membrane Proteins; C533201:pHLIP protein