A group from University of Chittagong, Bangladesh (containing this blog admin), etc. has reported about R-type lectin, Perinereis nuntia lectin (PnL), isolated from Marine Annelids.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8399747/
Previously, authors isolated PnL, a d-galactose-binding lectin of the R-type lectin family from Perinereis sp.
R-type lectins are derived from the ricin B-chain, a protein toxin consisting of AB subunits, in castor bean seeds. They usually have the three-leaf clover-like β-trefoil fold with Gln-X-Trp (Q-X-W) sequences in each subdomain. Why annelids have R-type lectins, and what physiological functions R-type lectins in annelids have are still uinclear. It would be the first step to identify locations where RnL is expressed.
Overall, PnL was found in extracellular locations after secretion from specific cells at the epidermis, setae, oblique muscle, acicula, nerve cord, and nephridium.
Interestingly, the localization pattern of the Gal/GalNAc-containing glycans was found to be almost identical to the distribution of PnL.
This co-localization is so interesting for blog admin, because the phytotoxin ricin is galactose-specific and clearly targets animal cells. What PnL is really doing?