Abstract
Brevinins are an important antimicrobial peptide (AMP) family discovered in the skin secretions of Ranidae frogs. The members demonstrate a typical C-terminal ranabox, as well as a diverse range of other structural characteristics. In this study, we identified a novel brevinin-2 peptide from the skin secretion of Sylvirana guentheri, via cloning transcripts, and identifying the expressed mature peptide, in the skin secretion. The confirmed amino acid sequence of the mature peptide was designated brevinin-2GHk (BR2GK). Moreover, as a previous study had demonstrated that the N-terminus of brevinin-2 is responsible for exerting antimicrobial activity, we also designed a series of truncated derivatives of BR2GK. The results show that the truncated derivatives exhibit significantly improved antimicrobial activity and cytotoxicity compared to the parent peptide, except a Pro14 substituted analog. The circular dichroism (CD) analysis of this analog revealed that it did not fold into a helical conformation in the presence of either lipopolysaccharides (LPS) or TFE, indicating that position 14 is involved in the formation of the α-helix. Furthermore, three more analogs with the substitutions of Ala, Lys and Arg at the position 14, respectively, revealed the influence on the membrane disruption potency on bacteria and mammalian cells by the structural changes at this position. Overall, the N-terminal 25-mer truncates demonstrated the potent antimicrobial activity with low cytotoxicity.
Highlights
Amphibian skin secretions act as the first line of defense against microorganisms, where antimicrobial peptides (AMPs) in the skin secretions play an important role [1]
The Brevinins have proved to be a remarkable AMP superfamily that contains a wide range of structural characteristics and which possess potent bioactivities [5,6]
The brevinin-2 subfamily has often been further grouped into subfamilies based on their specific structural characteristics, like the length of amino acid sequence, or the amino acid constitution within the
Summary
Amphibian skin secretions act as the first line of defense against microorganisms, where antimicrobial peptides (AMPs) in the skin secretions play an important role [1]. Amphibian AMPs are derived from ancient defensive genes and have developed to be diverse structures during evolution [1,2,3]. Amphibian skin-derived AMPs have been classified into several families based on structural similarities, such as dermaseptin and phylloseptin from Hylidae frogs, and brevinin, esculentin and temporin from Ranidae frogs [2,3]. Brevinin was discovered in the last century, initially from the skin secretion of Rana brevipoda porsa [4]. The primary structure of brevinin peptides demonstrates a high degree of variation between the family members discovered from different species, most possess a unique disulfate loop structure, “ranabox”, at the C-terminus [5,6]. With the subsequent isolation of brevinin related peptides
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