Pseudin

Pseudin is a peptide derived from Pseudis paradoxa.^[1] Pseudins have some antimicrobial function.^[2][3]

There are several different forms:

• pseudin-1^[4]
• pseudin-2 -- has been proposed as a treatment for type 2 diabetes.^[5][6]
• pseudin-4^[7]

Pseudin-2

Pseudin-2 is the most abundant version of the pseudins found on the skin of the paradoxical frog.^[8] The primary sequence reads as GLNALKKVFQGIHEAIKLINNHVQ. Its secondary/tertiary structure consists of one cationic amphipathic α-helix.^[8][9]

Antibacterial activity

Pseudin-2 was shown to have potent antibacterial activity, but a lower cytotoxicity.^[8] The cytotoxicity of a peptide can be measured by its effect on human erythrocytes.^[9] It takes a lower concentration of Pseudin-2 to kill bacteria or fungi such as E. coli, S. aureus, and C. albicans than to kill human erythrocytes.^[8] It is hypothesized that Pseudin-2 binding to the cell membrane of the bacteria results in a conformational change in which the peptide forms an α-helical shape, which allows it to perform cell lysis by inserting itself in the hydrophobic portion of the membrane.^[8][9] This mechanism is applicable to similar amphipathic α-helical peptides created by many frog species, although most of these peptides aren't very potent against bacteria.^[10] By increasing the cationicity and amphipathic nature of the molecule, it is possible to create analogues of Pseudin-2 that are even more selective towards bacteria. This is done by substituting leucine residues with lysine residues and glycine residues with proline residues, which results in two shorter α-helices (linked by the substituted proline) that are more attuned to penetrating bacterial cell membranes.^[9]

See also

• Exenatide