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

Journal article

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 K(D) 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.

Authors: Hansson, K; Ma, X; Eliasson, L; Czerwiec, E; Furie, B

• Publication status: Published
• Journal: Journal of biological chemistry
• Volume: 279
• Issue: 31
• Pages: 32453-32463
• Publication date: 2004-07-01
• DOI: 10.1074/jbc.m313825200
• EISSN: 1083-351X
• ISSN: 0021-9258
• Language: English
• Keywords: Protein Structure, Tertiary; 1-Carboxyglutamic Acid; Dose-Response Relationship, Drug; Animals; Disulfides; Snails; DNA, Complementary; Peptide Biosynthesis; Chromatography, High Pressure Liquid; Base Sequence; Mollusk Venoms; Cations; Time Factors; Molecular Sequence Data; Sequence Homology, Amino Acid; Kinetics; Calcium Channels; Tryptophan; Protein Processing, Post-Translational; Peptides; Peptides, Cyclic; Electrophysiology; Spectrometry, Mass, Electrospray Ionization; Calcium; Protein Binding; Spectrometry, Fluorescence; Hydrolysis; Amino Acid Sequence; Ions