Structure--activity analysis of buforin II, a histone H2A-derived antimicrobial peptide: The proline hinge is responsible for the cell-penetrating ability of buforin lI

摘要

Buforin II is a 21-aa potent antimicrobial peptide that forms. in a hydrophobic medium, an amphipathic structure consisting of an N-terminal random coil region (residues 1--4), an extended helical region (residues 5--10), a hinge (residue 11), and a C-terminal regular α-helical region (residues 12--21 ). To elucidate the structural features of buforin II that are required for its potent antimicrobial activity, we synthesized a series of N- and C-terminally truncated or amino acid-substituted synthetic buforin ll analogs and exam- ined their antimicrobial activity and mechanism of action. Deletion of the N-terminal random coil region increased the antibacterial attivity ≈2-fold, but further N-terminal truncation yielded peptide analogs with progressively decreasing activity. Removal of four amino acids from the C-terminal end of buforin ll resulted in a complete loss of antimicrobial activity. The substitution of leucine for the proline hinge decreased significantly the antimicrobial activity. Confocal fluorescence microscopic studies showed that buforin II analogs with a proline hinge penetrated the cell mem- brane without permeabilization and accumulated in the cytoplasm. However, removal of the proline hinge abrogated the ability of the peptide to enter cells. and buforin II analogs without a proline hinge localized on the cell surface, permeabilizing the cell mem- brane. In addition, the cell-penetrating efficiency of buforin ll and its truncated analogs, which depended on the alfa-helical content of the peptides, correlated linearly with their antimicrobial potency. Our results demonstrate clearly that the proline hinge is respon- sible for the cell-penetrating ability of buforin ll, and the cell- penetrating efficiency determines the antimicrobial potency of the peptide.