tachyplesin-peptide--tachypleus-tridentatus and dimethyl-sulfate

In view of the cationic amphipathic structure of tachyplesin I and antiparallel beta-sheet as a general DNA binding motif, DNA binding of the antimicrobial peptide has been examined. Several footprinting-like techniques using DNase I protection, dimethyl sulfate protection, and bleomycin- (BLM-) induced DNA cleavage were applied in this study. Some distinct footprints with DNase I are detected, and also the sequence-specific cleavage mode of the BLM-Fe(II) complex clearly is altered in the presence of tachyplesin I. In addition, methylation of the N-7 residue of guanine situated in the DNA major groove is not entirely inhibited (or activated) by tachyplesin I. The results suggest that tachyplesin I interacts with the minor groove of DNA duplex. Disappearance of the footprints by dithiothreitol-treated tachyplesin I and Ala-tachyplesin strongly suggests a significant contribution of secondary structure containing an antiparallel beta-sheet to the DNA binding of tachyplesin I. This is the first report on DNA interaction with a small peptide which contains a unique antiparallel beta-sheet structure. The mechanism for antimicrobial action of tachyplesin I has also been inferred.

Topics: Amino Acid Sequence; Anti-Infective Agents; Antimicrobial Cationic Peptides; Base Sequence; Binding Sites; Bleomycin; Circular Dichroism; Deoxyribonuclease I; Dithiothreitol; DNA; DNA-Binding Proteins; Molecular Sequence Data; Peptides; Peptides, Cyclic; Protein Conformation; Structure-Activity Relationship; Sulfuric Acid Esters