Peptide name : Citropin modified peptide-18

Source/Organism : Amphibian skin secretions

Linear/Cyclic : Linear

Chirality : L

Peptide length: 16

C-terminal modification: Linear

N-terminal modification : Amidation

Non-natural peptide information: None

Assay type : Sulforhodamine B assay

Assay time : Not found

Activity : IC50 : >10 µM

Cell line : Liver tumor celline

Cancer type : Liver cancer

Other activity : Anti-microbial activity

Amino acid composition bar chart :

Molecular mass : 1754.2135 Dalton

Aliphatic index : 1.706

Instability index : 34.5625

Hydrophobicity (GRAVY) : 1.2625

Isoelectric point : 12

Charge (pH 7) : 3.7581

Aromaticity : 0.062

Molar extinction coefficient (cysteine, cystine): (0, 0)

Hydrophobic/hydrophilic ratio : 3

hydrophobic moment : -0.118

Missing amino acid : C,W,H,Q,T,P,M,E,S,D,Y,N

Most occurring amino acid : A

Most occurring amino acid frequency : 3

Least occurring amino acid : G

Least occurring amino acid frequency : 1

Secondary structure fraction (Helix, Turn, Sheet): (0.4, 0.0, 0.5)

SMILES Notation: CC[C@H](C)[C@H](NC(=O)[C@@H](NC(=O)[C@H](C)NC(=O)[C@H](C)NC(=O)[C@@H](NC(=O)[C@H](CCCCN)NC(=O)[C@H](CCCCN)NC(=O)[C@@H](NC(=O)[C@@H](NC(=O)[C@H](C)NC(=O)[C@H](Cc1ccccc1)NC(=O)[C@H](CC(C)C)NC(=O)CN)C(C)C)[C@@H](C)CC)C(C)C)C(C)C)C(=O)N[C@@H](CCCNC(=N)N)C(=O)N[C@@H](CCCNC(=N)N)C(=O)N[C@@H](CC(C)C)C(=O)O

1 : Doyle J, et al. nNOS inhibition, antimicrobial and anticancer activity of the amphibian skin peptide, citropin 1.1 and synthetic modifications. The solution structure of a modified citropin 1.1. Eur J Biochem. 2003; 270:1141-53. doi: 10.1046/j.1432-1033.2003.03462.x

2 : Wong H, et al. The solution structure and activity of caerin 1.1, an antimicrobial peptide from the Australian green tree frog, Litoria splendida. Eur J Biochem. 1997; 247:545-57. doi: 10.1111/j.1432-1033.1997.00545.x

Paper title : nNOS inhibition, antimicrobial and anticancer activity of the amphibian skin peptide, citropin 1.1 and synthetic modifications. The solution structure of a modified citropin 1.1.

Doi : https://doi.org/10.1046/j.1432-1033.2003.03462.x

Abstract : A large number of bioactive peptides have been isolated from amphibian skin secretions. These peptides have a variety of actions including antibiotic and anticancer activities and the inhibition of neuronal nitric oxide synthase. We have investigated the structure-activity relationship of citropin 1.1, a broad-spectrum antibiotic and anticancer agent that also causes inhibition of neuronal nitric oxide synthase, by making a number of synthetically modified analogues. Citropin 1.1 has been shown previously to form an amphipathic alpha-helix in aqueous trifluoroethanol. The results of the structure-activity studies indicate the terminal residues are important for bacterial activity and increasing the overall positive charge, while maintaining an amphipathic distribution of residues, increases activity against Gram-negative organisms. Anticancer activity generally mirrors antibiotic activity suggesting a common mechanism of action. The N-terminal residues are important for inhibition of neuronal nitric oxide synthase, as is an overall positive charge greater than three. The structure of one of the more active synthetic modifications (A4K14-citropin 1.1) was determined in aqueous trifluoroethanol, showing that this peptide also forms an amphipathic alpha-helix.

Paper title : The solution structure and activity of caerin 1.1, an antimicrobial peptide from the Australian green tree frog, Litoria splendida.

Doi : https://doi.org/10.1111/j.1432-1033.1997.00545.x

Abstract : Caerin 1.1 is one of the major antimicrobial peptides isolated from the skin of the Australian green tree frog, Litoria splendida. Two-dimensional 1H-1H and 1H-13C NMR spectroscopy in trifluoroethanol/H2O (50:50, by vol.) have been used to assign the 1H and 13C-NMR spectra of this 25-amino-acid peptide. From an examination of these data, and using distance geometry and molecular dynamics calculations, the solution conformation of caerin 1.1 has been determined. The peptide adopts two well-defined helices from Leu2 to Lys11 and from Val17 to His24 separated by a region of less-defined helicity and greater flexibility. Overall, the peptide has a distinct amphipathic charge distribution. The solution structure of caerin 1.1 is compared with activity data against a variety of micro-organisms for the parent peptide and some naturally occurring and synthetic variants of caerin 1.1. The structural and activity data are consistent with caerin 1.1 interacting with membranes in a similar manner to other antimicrobial peptides, i.e. via a carpet-like mechanism whereby the individual peptides aggregate in a helical manner and orient themselves parallel to the membrane in a sheet-like arrangement [Shai, Y. (1995) Trends Biochem. Sci. 20, 460-464].