Structure-function relationships of tachyplesins and their analogues.
Haemocytes of the horseshoe crab (Limulus) contain a new family of arthropodous peptide antibiotics, termed the tachyplesin family. These cationic peptides are composed of 17-18 amino acid residues with a C-terminal arginine alpha-amide. Tachyplesin I takes on a fairly rigid conformation constrained by two disulphide bridges and adopts a conformation consisting of an antiparallel beta-sheet connected by a beta-turn. Isopeptides of tachyplesin I with amino acid replacements, tachyplesins II and III, and polyphemusins I and II have also been found in the haemocytes of the South-East Asian species and Limulus polyphemus. These peptides are present in abundance in the small granules of the haemocytes and inhibit strongly the growth of not only Gram-negative and Gram-positive bacteria but also fungi such as Candida albicans. Tachyplesin exists in the prepro form consisting of 77 residues; this precursor is probably processed by intracellular proteases and an amidation enzyme before incorporation into the small granules of the haemocytes. We examined the mode of action of tachyplesin I on biomembranes, comparing it with that of gramicidin S. Tachyplesin caused an efflux of K+ from Staphylococcus aureus and Escherichia coli cells similar to that caused by gramicidin S. Another antimicrobial substance, anti-LPS factor, has been isolated from haemocytes.
Iwanaga
S
S
Department of Molecular Biology, Graduate School of Medical Science, Kyushu University, Fukuoka, Japan.
Muta
T
T
Shigenaga
T
T
Seki
N
N
Kawano
K
K
Katsu
T
T
Kawabata
S
S
D000595:Amino Acid Sequence; D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry* / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000494:pharmacology*; D006737:Horseshoe Crabs / Q000378:metabolism; D008969:Molecular Sequence Data; D010456:Peptides, Cyclic / Q000737:chemistry* / Q000494:pharmacology*; D013329:Structure-Activity Relationship
D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; D004268:DNA-Binding Proteins; D010456:Peptides, Cyclic; C057636:tachyplesin peptide, Tachypleus tridentatus