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The spread of multidrug resistant bacteria owing to the intensive use of antibiotics is challenging current antibiotic therapies, and making the discovery and evaluation of new antimicrobial agents a high priority. The evaluation of novel peptide sequences of predicted antimicrobial peptides from different sources is valuable approach to identify alternative antibiotic leads. Two strategies were pursued in this study to evaluate novel antimicrobial peptides from the human β‐defensin family (hBD). In the first, a 32‐residue peptide was designed based on the alignment of all available hBD primary structures, while in the second a putative 35‐residue peptide, hBD10, was mined from the gene DEFB110. Both hBDconsensus and hBD10 were chemically synthesized, folded and purified. They showed antimicrobial activity against Escherichia coli, Staphylococcus aureus, and Mycobacterium tuberculosis, but were not hemolytic on human red blood cells. The NMR‐based solution structure of hBDconsensus revealed that it adopts a classical β‐defensin fold and disulfide connectivities. Even though the mass spectrum of hBD10 confirmed the formation of three disulfide bonds, it showed limited dispersion in 1H NMR spectra and structural studies were not pursued. The evaluation of different β‐defensin structures may identify new antimicrobial agents effective against multidrug‐resistant bacterial strains. [ABSTRACT FROM AUTHOR]

Abstract: Rapid progress in transcriptomic and proteomic studies of sea anemones has led to the identification of a large number of new peptide sequences. Some of these peptides have high sequence similarity and identical cysteine frameworks to those of previously reported sequences. One such peptide we have identified from a transcriptomic study of Oulactis sp is OspTx2a, which has a cysteine framework similar to that of ShK (from Stichodactyla helianthus) and BgK (from Bunodosoma granulifera). This peptide was made using solid‐phase peptide synthesis, but, upon oxidative folding, it generated two peptides with identical masses (OspTx2a‐p1 and OspTx2a‐p2) that were distinguishable by high‐performance liquid chromatography. The structures of OspTx2a‐p1 and OspTx2a‐p2 were determined using nuclear magnetic resonance spectroscopy, and voltage‐clamp electrophysiology assays were performed in order to assess the activity against a range of potassium channels. The structures of the two peptides were very similar to each other and to BgK, with the same disulfide bond connectivities, and both had an all‐trans backbone conformation. In functional assays, both OspTx2a‐p1 and OspTx2a‐p2 inhibited KV1.2 and KV1.6 channel currents at low µM concentrations, with similar but not identical IC50 values. Peptides containing a C‐terminal Cys residue are particularly sensitive to racemization at this residue, and the two products obtained for OspTx2a could be a consequence of racemization of the Cys residue at its C‐terminus during synthesis. NMR chemical shift differences between the two products and their structural preferences for a d‐Cys residue were consistent with this interpretation. [ABSTRACT FROM AUTHOR]