1. Bioevaluation of Ranatuerin-2Pb from the Frog Skin Secretion of Rana pipiens and its Truncated Analogues
Xiaowei Zhou, Daning Shi, Ruimin Zhong, Zhuming Ye, Chengbang Ma, Mei Zhou, Xinping Xi, Lei Wang, Tianbao Chen, Hang Fai Kwok Biomolecules. 2019 Jun 25;9(6):249. doi: 10.3390/biom9060249.
Antimicrobial peptides (AMPs) are considered as a promising agent to overcome the drug-resistance of bacteria. Large numbers of AMPs have been identified from the skin secretion of Rana pipiens, including brevinins, ranatuerins, temporins and esculentins. In this study, the cDNA precursor of a broad-spectrum antimicrobial peptide, ranatuerin-2Pb, was cloned and identified. Additionally, two truncated analogues, RPa and RPb, were synthesised to investigate the structure-activity relationship of ranatuerin-2Pb. RPa lost antimicrobial activity against Candida albicans, MRSA, Enterococcus faecalis and Pseudomonas aeruginosa, while RPb retained its broad-spectrum antimicrobial activity. Additionally, ranatuerin-2Pb, RPa and RPb demonstrated inhibition and eradication effects against Staphylococcusaureus biofilm. RPb showed a rapid bacterial killing manner via membrane permeabilization without damaging the cell membrane of erythrocytes. Moreover, RPb decreased the mortality of S. aureus infected Galleria mellonella larvae. Collectively, our results suggested that RPb may pave a novel way for natural antimicrobial drug design.
2. Antimicrobial properties of the frog skin peptide, ranatuerin-1 and its [Lys-8]-substituted analog
Agnes Sonnevend, Floyd C Knoop, Mahrendra Patel, Tibor Pál, Ana Maria Soto, J Michael Conlon Peptides. 2004 Jan;25(1):29-36. doi: 10.1016/j.peptides.2003.11.011.
The predicted conformation of ranatuerin-1 (SMLSVLKNLG(10)KVGLGFVACK(20)INK QC), an antimicrobial peptide first isolated from the skin of the bullfrog Rana catesbeiana, comprises three structural domains: alpha-helix (residues 1-8), beta-sheet (residues 11-16) and beta-turn (residues 20-25). Circular dichroism studies confirm significant alpha-helical character in 50% trifluoroethanol. Replacement of Cys-19 and Cys-25 by serine resulted only in decreased antimicrobial potency but deletion of either the cyclic heptapeptide region [residues (19-25)] or the N-terminal domain [residues (1-8)] produced inactive analogs. Substitution of the glycine residues in the central domain of the [Ser-19, Ser-25] analog by lysine produced inactive peptides despite increased alpha-helical content and cationicity. The substitution Asn-8-->Lys gave a ranatuerin-1 analog with increased alpha-helicity and cationicity and increased potency against a range of Gram-positive and Gram-negative bacteria and against C. albicans but only a small increase (21%) in hemolytic activity. In contrast, increasing alpha-helicity and hydrophobicity by the substitution Asn-22-->Ala resulted in a 3.5-fold increase in hemolytic activity. Effects on antimicrobial potencies of substitutions of neutral amino acids at positions 4, 18, 22, and 24 by lysine were less marked. Strains of pathogenic E. coli from different groups showed varying degrees of sensitivity to ranatuerin-1 (MIC between 5 and 40 microM) but [Lys-8] ranatuerin-1 showed increased potency (between 2- and 8-fold; P < 0.01) against all strains. The data demonstrate that [Lys-8] ranatuerin-1 shows potential as a candidate for drug development.
3. Ranatuerin 1T: an antimicrobial peptide isolated from the skin of the frog, Rana temporaria
J Goraya, F C Knoop, J M Conlon Peptides. 1999;20(2):159-63. doi: 10.1016/s0196-9781(98)00174-0.
A peptide, termed ranatuerin 1T, with growth-inhibiting activity toward Staphylococcus aureus, was isolated from an extract of the skin of the European brown frog, Rana temporaria. The primary structure of the peptide was established as: GLLSGLKKVG10 KHVAKNVAVS20LMDSLKCKIS30GDC. In common with other anti-microbial peptides from Ranid frogs, (e.g., ranalexin, ranatuerins, gaegurins, brevinins, esculetins, rugosins), ranatuerin IT contains an intramolecular disulfide bridge forming a heptapeptide ring but there is little structural similarity outside this cyclic region. The minimum inhibitory concentration (MIC) of ranatuerin 1T was 120 microM against the Gram-positive bacterium S. aureus and 40 microM against the Gram-negative bacterium Escherichia coli, but the peptide was not active against the yeast Candida albicans.
