Figure 1.

Nemertide structure, sources, and sequences. (A) Solution NMR structure of nemertide α 1 (PDB id 6ENA). The three disulfide bonds at the core of the molecule are numbered (in Roman numerals) and marked in yellow. Numerals mark the loops. (B) Schematic phylogenetic tree of α nemertide expressing species identified on the transcriptomic level. The tree is redrawn from Ament-Velásques et al. 2016.¹² *: No α nemertide was found in L. viridis. (C) Top: consensus α nemertide sequence with the variable positions marked as numbers. Roman numerals mark cysteines, and the ICK disulfide connectivity (I–IV, II–V, III–VI) is displayed with black bars. Loop number in numerals; number of residues in parentheses. Bottom: Sequence alignment of nemertides, including the truncated α-8. P*: hydroxyproline (Hyp). With the exception of 1 and 2, the α nemertides have so far been identified only in transcriptomic data from the marine Lineideae family of nemertean worms (genus: Lineus: 4 sp., Ramphogordius: 1 sp., and a partial sequence in Riseriellus: 1 sp.) The partial contig of 8 from the R. occultus transcriptome was omitted from this study since the full C-terminal sequence was unknown.