The first gamma-carboxyglutamic acid-containing contryphan - A selective L-type calcium ion channel blocker isolated from the venom of conus marmoreus

Summary, in English

Contryphans constitute a group of conopeptides that are known to contain an unusual density of post-translational modifications including tryptophan bromination, amidation of the C-terminal residue, leucine, and tryptophan isomerization, and proline hydroxylation. Here we report the identification and characterization of a new member of this family, glacontryphan-M from the venom of Conus marmoreus. This is the first known example of a contryphan peptide carrying glutamyl residues that have been post-translationally carboxylated to {gamma}-carboxyglutamyl (Gla) residues. The amino acid sequence of glacontryphan-M was determined using automated Edman degradation and electrospray ionization mass spectrometry. The amino acid sequence of the peptide is: Asn-Gla-Ser-Gla-Cys-Pro-D-Trp-His-Pro-Trp-Cys. As with most other contryphans, glacontryphan-M is amidated at the C terminus and maintains the five-residue intercysteine loop. The occurrence of a D-tryptophan residue was confirmed by chemical synthesis and HPLC elution profiles. Using fluorescence spectroscopy we demonstrated that the Gla-containing peptide binds calcium with a KD of 0.63 mM. Cloning of the full-length cDNA encoding glacontryphan-M revealed that the primary translation product carries an N-terminal signal/propeptide sequence that is homologous to earlier reported contryphan signal/propeptide sequences up to 10 amino acids preceding the toxin region. Electrophysiological experiments, carried out on mouse pancreatic B-cells, showed that glacontryphan-M blocks L-type voltage-gated calcium ion channel activity in a calcium-dependent manner. Glacontryphan-M is the first contryphan reported to modulate the activity of L-type calcium ion channels.

• Author: Karin M Hansson; Xiaosong Ma; Lena Eliasson; Eva Czerwiec; Bruce Furie; Barbara C. Furie; Patrik Rorsman; Johan Stenflo
• Department/s: Clinical Chemistry, Malmö; Department of Experimental Medical Science; Diabetes - Islet Cell Exocytosis; Islet cell physiology
• Publishing year: 2004
• Language: English
• Pages: 32453-32463
• Publication/Series: Journal of Biological Chemistry
• Volume: 279
• Issue: 31
• Links: http://dx.doi.org/10.1074/jbc.M313825200
• Document type: Journal article
• Publisher: American Society for Biochemistry and Molecular Biology
• Topic: Medicinal Chemistry; Endocrinology and Diabetes
• Status: Published
• Research group: Clinical Chemistry, Malmö; Diabetes - Islet Cell Exocytosis; Islet cell physiology
• ISBN/ISSN/Other: ISSN: 1083-351X