title: A bifunctional sea anemone peptide with Kunitz type protease and potassium channel inhibiting properties.
abstract: Sea anemone venom is a known source of interesting bioactive compounds, including peptide toxins which are invaluable tools for studying structure and function of voltage-gated potassium channels. APEKTx1 is a novel peptide isolated from the sea anemone Anthopleura elegantissima, containing 63 amino acids cross-linked by 3 disulfide bridges. Sequence alignment reveals that APEKTx1 is a new member of the type 2 sea anemone peptides targeting voltage-gated potassium channels (K(V)s), which also include the kalicludines from Anemonia sulcata. Similar to the kalicludines, APEKTx1 shares structural homology with both the basic pancreatic trypsin inhibitor (BPTI), a very potent Kunitz-type protease inhibitor, and dendrotoxins which are powerful blockers of voltage-gated potassium channels. In this study, APEKTx1 has been subjected to a screening on a wide range of 23 ion channels expressed in Xenopus laevis oocytes: 13 cloned voltage-gated potassium channels (K(V)1.1-K(V)1.6, K(V)1.1 triple mutant, K(V)2.1, K(V)3.1, K(V)4.2, K(V)4.3, hERG, the insect channel Shaker IR), 2 cloned hyperpolarization-activated cyclic nucleotide-sensitive cation non-selective channels (HCN1 and HCN2) and 8 cloned voltage-gated sodium channels (Na(V)1.2-Na(V)1.8 and the insect channel DmNa(V)1). Our data show that APEKTx1 selectively blocks K(V)1.1 channels in a very potent manner with an IC(50) value of 0.9nM. Furthermore, we compared the trypsin inhibitory activity of this toxin with BPTI. APEKTx1 inhibits trypsin with a dissociation constant of 124nM. In conclusion, this study demonstrates that APEKTx1 has the unique feature to combine the dual functionality of a potent and selective blocker of K(V)1.1 channels with that of a competitive inhibitor of trypsin.
authors.affiliation: Laboratory of Toxicology, University of Leuven (K.U. Leuven), Campus Gasthuisberg O&N2, Herestraat, Belgium. jan.tytgat@pharm.kuleuven.be
authors.forename: Steve
authors.initials: S
authors.lastname: Peigneur
authors.forename: Bert
authors.initials: B
authors.lastname: Billen
authors.forename: Rita
authors.initials: R
authors.lastname: Derua
authors.forename: Etienne
authors.initials: E
authors.lastname: Waelkens
authors.forename: Sarah
authors.initials: S
authors.lastname: Debaveye
authors.forename: László
authors.initials: L
authors.lastname: Béress
authors.forename: Jan
authors.initials: J
authors.lastname: Tytgat
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D003064:Cnidarian Venoms / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D008969:Molecular Sequence Data; D009865:Oocytes / Q000187:drug effects / Q000502:physiology; D010455:Peptides / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D026902:Potassium Channel Blockers / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D024642:Potassium Channels, Voltage-Gated / Q000037:antagonists & inhibitors*; D011480:Protease Inhibitors / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D012615:Sea Anemones / Q000502:physiology*; D016415:Sequence Alignment; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods; D014981:Xenopus
chemical_list: C559902:APEKTx1 peptide, Anthopleura elegantissima; D003064:Cnidarian Venoms; D010455:Peptides; D026902:Potassium Channel Blockers; D024642:Potassium Channels, Voltage-Gated; D011480:Protease Inhibitors