Tachyplesin

Tachyplesin I (TPI) is an antimicrobial polypeptide originally detected in Japanese Horse Shoe Crab.

The antimicrobial activity of peptides is closely related to the composition of the pathogen membrane. Bacteria and fungi have negatively charged membranes, and the interaction of is mediated in large part by electrostatic interactions^[1] (you can see the Hydrophobic and Polar amino acids). It shows high affinity for lipopolysaccharides (LPS) of gram-negative bacteria, thus neutralizing its effects. It has also been reported to inhibit the growth of gram positive bacteria, fungui and viruses.

Structural highlights

The aminoacid sequence of the TPI is H-Lys-Trp-Cys-Phe-Arg-Val-Cys-Tyr-Arg-Gly-Ile-Cys-Tyr-Arg-Arg-Cys-Arg-NH₂ with between Cys³-Cys¹⁶ and Cys⁷-Cys¹², and its C-terminus is amidated.

Image:Scheme.jpg

Besides, there exists H-bond and aromatic ring stacking interactions which helps stabilizing the hairpin loop structure of the peptide.

There are three linear derivatives: , TPF4 and TPA4. Since linear tachyplesin analogues do not show preferential affinity for LPS, the hairpin properties of the peptide seems to be important for recognition of lipopolysaccharides and its biological activities. TPI undergoes confirmation change in . The backbone of the polypeptide becomes more rigid and twisted in presence of LPS, than in the , making it more stable.

Importance

The activity of Tachyplesin I is derived from its ability to permeabilize the cell membranes of pathogens.^[1]

Relevance

Mode of action

TPI can bind to LPS and also has ability to permeabilize the cell membrane of pathogens. Docking model suggests strong affinity to LPS gained by interaction between cationic residues of TPI with phosphate group and sachharides of LPS. Furthermore, interaction between hydrophobic residues of TPI with acyl chains of LPS strengthens the TPI/LPS interaction.

Function

This is a sample scene created with SAT to by Group, and another to make of the protein. You can make your own scenes on SAT starting from scratch or loading and editing one of these sample scenes.