MEMBRANE PERMEABILIZATION AND EFFICIENT GENE-TRANSFER BY A PEPTIDE-CONTAINING SEVERAL HISTIDINES

We designed a peptide, H5WYG (GLFHAIAHFIHGGWHGLIHGWYG), that permeabil izes cell membrane at a slightly acidic pH but not at neutral pH. Abso rbance, fluorescence, and circular dichroism spectra showed that H5WYG undergoes a dramatic conformational change between pH 7.0 and 6.0 tha t correlates with the protonation of the histidyl residues. Cell perme abilization studies monitored by flow cytometry on living cells showed that H5WYG permeabilizes the cell membrane with a great efficiency at pH 6.4 but was not active at neutral pH; at pH 6.8, the peptide perme abilized 50% of the cells at 20 degrees C within 10 min. H5WYG increas ed the expression of genes transferred to cells as glycosylated polyly sine-DNA complexes, and the transfection efficiency was not impaired i n the presence of serum. Therefore, this peptide containing several hi stidines that become positively charged when the pH decreased to less than 7.0 is a suitable helper for delivering molecules into the cytoso l upon either permeabilization of the plasma membrane induced by lower ing the extracellular medium to pH 6.4 or permeabilization of the endo somal membrane induced by acidification of endosomes.