Sea anemone toxins affecting potassium channels.
The great diversity of K(+) channels and their wide distribution in many tissues are associated with important functions in cardiac and neuronal excitability that are now better understood thanks to the discovery of animal toxins. During the past few decades, sea anemones have provided a variety of toxins acting on voltage-sensitive sodium and, more recently, potassium channels. Currently there are three major structural groups of sea anemone K(+) channel (SAK) toxins that have been characterized. Radioligand binding and electrophysiological experiments revealed that each group contains peptides displaying selective activities for different subfamilies of K(+) channels. Short (35-37 amino acids) peptides in the group I display pore blocking effects on Kv1 channels. Molecular interactions of SAK-I toxins, important for activity and binding on Kv1 channels, implicate a spot of three conserved amino acid residues (Ser, Lys, Tyr) surrounded by other less conserved residues. Long (58-59 amino acids) SAK-II peptides display both enzymatic and K(+) channel inhibitory activities. Medium size (42-43 amino acid) SAK-III peptides are gating modifiers which interact either with cardiac HERG or Kv3 channels by altering their voltage-dependent properties. SAK-III toxins bind to the S3C region in the outer vestibule of Kv channels. Sea anemones have proven to be a rich source of pharmacological tools, and some of the SAK toxins are now useful drugs for the diagnosis and treatment of autoimmune diseases.
Diochot
Sylvie
S
Institut de Pharmacologie Moléculaire et Cellulaire, Centre National de la Recherche Scientifi que, Université de Nice-Sophia-Antipolis, 660 Route des Lucioles, Valbonne, 06560, France.
Lazdunski
Michel
M
D000595:Amino Acid Sequence; D000818:Animals; D003064:Cnidarian Venoms / Q000737:chemistry / Q000633:toxicity; D006801:Humans; D008387:Marine Toxins / Q000737:chemistry / Q000633:toxicity*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D011487:Protein Conformation; D012615:Sea Anemones
C072544:BDS II protein, Anemonia sulcata; D003064:Cnidarian Venoms; D008387:Marine Toxins; D015221:Potassium Channels