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DOI: 10.1055/s-0030-1264475
New cystine knot peptides from a marine sponge Asteropus sp.
Four novel peptides 1–4 were isolated from a marine sponge Asteropus sp., collected off the coast of Geoje Island, Korea. The primary structures of the peptides were determined by automated Edman degradation and corroborated by MALDI-TOF MS spectrometry. Six Cys residues in each peptide formed three intramolecular disulfide bonds and arranged in the pattern -C-C-CC-C-C-, which characterizes the cystine knot peptides similar to some conotoxins and spider toxins. The solution structures of the peptides by 1D and 2D NMR revealed the N-terminus of each peptide to be blocked by a pyroglutamic acid. Unlike the common cystine knot peptides, each peptide exhibited highly negative charge, which might contribute to different biological functions. Peptide 1 exhibited moderate suppressive effects on NO production at the concentration of 100µM without significant cytotoxicity against the cells. In the neuraminidase inhibition assay, 1 showed mild activity with IC50 value of 181.69µM.
a Sequence identity compared to ABU8–1 |
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Peptide |
Sequence |
Isoelectric point |
Charge |
Identity (%)a |
ABU8–1 |
pEGCAFEGESCNVQFYPCCPGLGLTCIPGNPDGTCYYL |
3.33 |
–4 |
100 |
ABU8–2 |
pEGCAFEGESCNVEFYPCCPGLGLTCIPGNPDGTCYYL |
3.26 |
–5 |
97 |
ABU8–3 |
pEDCPGEGEQCDVEFNPCCPPLTCIPGDPYGICYII |
3.09 |
–7 |
59 |
ABU8-a |
pEGCAGPGEECIVGFYDCCPGYRCYPGDPGGICY |
3.64 |
–4 |
60 |