Antibacterial activities and conformations of synthetic alpha-defensin HNP-1 and analogs with one, two and three disulfide bridges.
Structure and biological activities of synthetic peptides corresponding to human alpha-defensin HNP-1, AC1YC2RIPAC3IAGERRYGTC4IYQGRLWAFC5C6 with the S-S connectivities: C1-C6, C2-C4, C3-C5, and its variants with one, two and three disulfide bridges were investigated. Oxidation of synthetic, reduced HNP-1 yielded a peptide with S-S connectivities C1-C3, C2-C4 and C5-C6, and not with the S-S linkages as in naturally occurring HNP-1. Selective protection of cysteine sulfhydryls was necessary for the formation of S-S bridges as in native HNP-1. Likewise, oxidation of peptide encompassing the segment from C2 to C5, resulted in the S-S linkages C2-C3 and C4-C5 instead of the expected linkage C2-C4 and C3-C5. Antibacterial activities were observed for all peptides, irrespective of how the S-S bridges were linked. Linear peptides without S-S bridges were inactive. Circular dichroism (CD) spectra suggest that peptides constrained by one and two S-S bridges do not form rigid beta-sheet structures in an aqueous environment. The spectrum of HNP-1 in an aqueous environment suggests the presence of a beta-hairpin conformation. In the presence of lipid vesicles, the S-S constrained peptides tend to adopt a beta-structure. Although the S-S connectivities observed in HNP-1 may be necessary for other physiological activities, such as chemotaxis, they are clearly not essential for antibacterial activity.
Mandal
M
M
Centre for Cellular and Molecular Biology, Hyderabad, India.
Nagaraj
R
R
D000595:Amino Acid Sequence; D000818:Animals; D002942:Circular Dichroism; D003553:Cystine / Q000032:analysis*; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects*; D006801:Humans; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology* / Q000633:toxicity; D011487:Protein Conformation; D011550:Pseudomonas aeruginosa / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D012995:Solubility; D013154:Spleen / Q000166:cytology; D013211:Staphylococcus aureus / Q000187:drug effects*; D013329:Structure-Activity Relationship; D013601:T-Lymphocytes / Q000187:drug effects; D014867:Water; D023084:alpha-Defensins / Q000737:chemistry / Q000494:pharmacology* / Q000633:toxicity
D010446:Peptide Fragments; D023084:alpha-Defensins; C406413:human neutrophil peptide 1; D014867:Water; D003553:Cystine; D004121:Dimethyl Sulfoxide