Antimicrobial peptides, isolated from horseshoe crab hemocytes, tachyplesin II, and polyphemusins I and II. Chemical structures and biological activity.

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  • Miyata Toshiyuki
    Department of Biology, Faculty of Science Graduate School of Medical Science, Kyushu University
  • Tokunaga Fuminori
    Department of Molecular Biology, Graduate School of Medical Science, Kyushu University
  • Yoneya Takashi
    Department of Biology, Faculty of Science Graduate School of Medical Science, Kyushu University
  • Yoshikawa Katsuhiro
    Department of Biology, Faculty of Science Graduate School of Medical Science, Kyushu University
  • Iwanaga Sadaaki
    Department of Biology, Faculty of Science Graduate School of Medical Science, Kyushu University|Department of Molecular Biology, Graduate School of Medical Science, Kyushu University
  • Niwa Makoto
    Department of Bacteriology, Osaka City University Medical School
  • Takao Toshifumi
    Institute for Protein Research, Osaka University
  • Shimonishi Yasutsugu
    Institute for Protein Research, Osaka University

抄録

Tachyplesin is an antimicrobial peptide recently found in the acid extract of hemocytes from the Japanese horseshoe crab (Tachypleus tridentatus)[Nakamura, T. et al.(1988) J. Biol. Chem. 263, 16709-16713]. In our continuing studies on the peptide, we have found an isopeptide, tachyplesin II, and also polyphemusins I and II in hemocytes of the American horseshoe crab (Limulus polyphemus). The complete primary structures of these peptides, which are very similar to that of the previously isolated peptide, now named tachyplesin I, were determined to be as follows:<BR>Polyphemusin I NH2-R-R-W-C-F-R-V-C-Y-R-G-F-C-Y-R-K-C-R-CONH2<BR>Polyphemusin II NH2-R-R-W-C-F-R-V-C-Y-K-G-F-C-Y-R-K-C-R-CONH2<BR>Tachyplesin II NH2-R-W-C-F-R-V-C-Y-R-G-I- C-Y-R-K-C-R-CONH2<BR>The isopeptide, tachyplesin II, consists of 17 residues with a COOH-terminal arginine α-amide. On the other hand, both polyphemusins I and II were found to contain 18 residues due to an additional Arg residue at the NH, -terminal end as well as a COOH-terminal arginine α-amide. The disulfide linkages for polyphemusin I consisted of two bridges between Cys-4 and Cys-17 and between Cys-8 and Cys-13, which was identical to in the case of tachyplesin I. Moreover, all of these peptides inhibited the growth of not only Gramnegative and-positive bacteria but also fungi, such as Candida albicans M9. Furthermore, complex formation between these peptides and bacterial lipopolysaccharides was also observed in a double diffusion test. These results suggest that tachyplesins and polyphemusins are probably located in the hemocyte membrane, where they act on antimicrobial peptides as a self-defense mechanism in the horseshoe crab against invading microorganisms.

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