Journal
TOXICON
Volume 51, Issue 2, Pages 218-229Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.toxicon.2007.09.006
Keywords
conotoxin; epimerization; D-amino acid; post-translational modifications; excitatory peptide
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Funding
- NIGMS NIH HHS [GM 48677] Funding Source: Medline
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The considerable diversity of Conus peptides in the I-1-superfamily provides a rare opportunity to define parameters important for the post-translational L- to D-isomerization of amino acids. This subtlest of post-translational modifications is not readily detectable by most techniques, and it would be a considerable advance if one could predict its potential occurrence purely from gene sequences. We previously described three I-1-conotoxins, i-RXIA (formerly designated r11a), r11b and r11c, each containing a D-amino acid at the third position from the C-terminus. In this work, we investigated two novel I-1-superfamily members, r11d and ar11a, which we show have only L-amino acids. Based on these observations and an analysis of cDNA sequences of other group members, we suggest that there is a rule to predict D-amino acids in I-1-superfamily peptides. Two factors are important: the residue to be modified should be three amino acids from the C-terminus of the precursor sequence, and it should be in a suitable sequence context. We apply the rule to other members of the I-1-superfarnily, to determine a priori which are probably modified. (c) 2007 Elsevier Ltd. All rights reserved.
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