Publication Date:
2022-05-25
Description:
Author Posting. © The Author(s), 2006. This is the author's version of the work. It is posted here by permission of Blackwell for personal use, not for redistribution. The definitive version was published in FEBS Journal 273 (2006): 2779-2788, doi:10.1111/j.1742-4658.2006.05355_1.x.
Description:
The cone snail is the only invertebrate system in which the vitamin K
dependent carboxylase (or γ-carboxylase) and its product γ-carboxyglutamic
acid (Gla)1 have been identified. It remains the sole source of structural
information of invertebrate γ-carboxylase subtrates. Four novel γ-
carboxyglutamic acid (Gla)1 containing peptides were purified from the
venom of Conus textile and characterized by biochemical methods and mass
spectrometry. The peptides Gla(1)-TxVI, Gla(2)-TxVI/A, Gla(2)-TxVI/B
and Gla(3)-TxVI each have 6 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 γ-carboxylation recognition site (γ-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 γ-carboxylase and synthetic
peptide substrates localized the γ-CRS of Gla(1)-TxVI to the region –14 to
–1 of the polypeptide precursor: the Km was reduced from 1.8 mM for Gla
(1)-TxVI lacking a propeptide to 24 μM when a 14-residue propeptide was
attached to the substrate. Similarly, addition of an 18-residue propeptide to
Gla(2)-TxVI/B reduced the Km 10-fold.
Description:
This work was supported by grants K2001-03X-04487-27A and K2001-
03GX-04487-27, 08647, 13147 from the Swedish Medical Research
Council, the European Union Cono-Euro-Pain (QLK3-CT-2000-00204), the
Swedish Foundation for Strategic Research, the Kock Foundation, the
Påhlsson Foundation and the Foundation of University Hospital, Malmö.
Keywords:
γ-carboxyglutamic acid
;
Vitamin K
;
Conotoxin
;
Conus textile
;
Propeptide
Repository Name:
Woods Hole Open Access Server
Type:
Preprint
Format:
901208 bytes
Format:
application/pdf
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