Novel gamma-carboxyglutamic acid-containing peptides from the venom of Conus textile
Författare
Summary, in English
The cone snail is the only invertebrate system in which the vitamin K-dependent carboxylase (or gamma-carboxylase) and its product gamma-carboxyglutamic acid (Gla) have been identified. It remains the sole source of structural information of invertebrate gamma-carboxylase substrates. Four novel Gla-containing peptides were purified from the venom of Conus textile and characterized using biochemical methods and mass spectrometry. The peptides Gla(1)-TxVI, Gla(2)-TxVI/A, Gla(2)-TxVI/B and Gla(3)-TxVI each have six Cys residues and belong to the O-superfamily of conotoxins. All four conopeptides contain 4-trans-hydroxyproline and the unusual amino acid 6-L >-bromotryptophan. Gla(2)-TxVI/A and Gla(2)-TxVI/B are isoforms with an amidated C-terminus that differ at positions +1 and +13. Three isoforms of Gla(3)-TxVI were observed that differ at position +7: Gla(3)-TxVI, Glu7-Gla(3)-TxVI and Asp7-Gla(3)-TxVI. The cDNAs encoding the precursors of the four peptides were cloned. The predicted signal sequences (amino acids -46 to -27) were nearly identical and highly hydrophobic. The predicted propeptide region (-20 to -1) that contains the gamma-carboxylation recognition site (gamma-CRS) is very similar in Gla(2)-TxVI/A, Gla(2)-TxVI/B and Gla(3)-TxVI, but is more divergent for Gla(1)-TxVI. Kinetic studies utilizing the Conus gamma-carboxylase and synthetic peptide substrates localized the gamma-CRS of Gla(1)-TxVI to the region -14 to -1 of the polypeptide precursor: the K-m was reduced from 1.8 mM for Gla (1)-TxVI lacking a propeptide to 24 mu M when a 14-residue propeptide was attached to the substrate. Similarly, addition of an 18-residue propeptide to Gla(2)-TxVI/B reduced the K-m value tenfold.
Avdelning/ar
Publiceringsår
2006
Språk
Engelska
Sidor
2779-2788
Publikation/Tidskrift/Serie
The FEBS Journal
Volym
273
Issue
12
Länkar
Dokumenttyp
Artikel i tidskrift
Förlag
Wiley-Blackwell
Ämne
- Biochemistry and Molecular Biology
Nyckelord
- vitamin K
- propeptide
- Conus textile
- gamma-carboxyglutamic acid
- conotoxin
Status
Published
Forskningsgrupp
- Clinical Chemistry, Malmö
ISBN/ISSN/Övrigt
- ISSN: 1742-464X