title: Homodimeric theta-defensins from rhesus macaque leukocytes: isolation, synthesis, antimicrobial activities, and bacterial binding properties of the cyclic peptides.
abstract: Rhesus theta-defensin 1 (RTD-1) is a unique tridisulfide, cyclic antimicrobial peptide formed by the ligation of two 9-residue sequences derived from heterodimeric splicing of similar 76-amino acid, alpha-defensin-related precursors, termed RTD1a and RTD1b (Tang, Y. Q., Yuan, J., Osapay, G., Osapay, K., Tran, D., Miller, C. J., Ouellette, A. J., and Selsted, M. E. (1999) Science 286, 498-502). The structures of RTD-2 and RTD-3 were predicted to exist if homodimeric splicing of the RTD1a and RTD1b occurs in vivo. Western blotting disclosed the presence of putative theta-defensins, distinct from RTD-1, in leukocyte extracts. Two new theta-defensins, RTD-2 and RTD-3, were purified by reverse-phase high performance liquid chromatography and characterized by amino acid analysis, matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy, and comparison to the synthetic standards. RTD-2 and RTD-3 are the predicted homodimeric splicing products of RTD1b and RTD1a, respectively. The cellular abundances of RTD-1, -2, and -3 were 29:1:2, indicating that there is a preference for the heterodimeric ligation that generates RTD-1. RTD-1, -2, and -3 had similar antimicrobial activities against Staphylococcus aureus, Candida albicans, and Cryptococcus neoformans, whereas the activity of RTD-2 against Escherichia coli was 2-3-fold less than those of RTD-1 and RTD-3. Equal amounts of each theta-defensin bound to E. coli cells, indicating that the differences in antibacterial activities are the result of post-binding processes.
authors.affiliation: Department of Pathology, University of California, Irvine, California 92697, USA.
authors.forename: Dat
authors.initials: D
authors.lastname: Tran
authors.forename: Patti A
authors.initials: PA
authors.lastname: Tran
authors.forename: Yi-Quan
authors.initials: YQ
authors.lastname: Tang
authors.forename: Jun
authors.initials: J
authors.lastname: Yuan
authors.forename: Tim
authors.initials: T
authors.lastname: Cole
authors.forename: Michael E
authors.initials: ME
authors.lastname: Selsted
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000900:Anti-Bacterial Agents / Q000097:blood* / Q000737:chemistry / Q000494:pharmacology; D001665:Binding Sites; D023082:Defensins / Q000097:blood* / Q000737:chemistry / Q000494:pharmacology; D019281:Dimerization; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000502:physiology; D007962:Leukocytes / Q000502:physiology*; D008253:Macaca mulatta; D008969:Molecular Sequence Data; D010456:Peptides, Cyclic / Q000097:blood* / Q000737:chemistry / Q000494:pharmacology; D011485:Protein Binding; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013440:Sulfides / Q000737:chemistry
chemical_list: D000900:Anti-Bacterial Agents; D023082:Defensins; D010456:Peptides, Cyclic; D013440:Sulfides; C447826:rhesus theta defensin-2; C447827:rhesus theta defensin-3