Legumin encoding sequences from the redwood family (Taxodiaceae) reveal precursors lacking the conserved Asn-Gly processing site.
We have cloned and sequenced two different cDNAs encoding legumins from Japanese red cedar (Cryptomeria japonica, Taxodiaceae). The derived amino acid sequences show between 34% and 55% identity when compared with legumins from angiosperms and from Pinaceae, respectively. The predicted precursors are unusual in that they contain potential glycosylation signals, and we have found the corresponding beta-polypeptides actually to be glycosylated. As most outstanding feature one of the precursors is lacking the Asn-Gly processing site which has been assumed to be highly conserved in legumin gene evolution. Legumin encoding sequences amplified from genomic DNA suggest that these unusual precursors are widespread if not ubiquitous in the Taxodiaceae family. From previous reports on legumin precursors with divergent processing sites, on the proteases involved in legumin precursor processing and from the results presented here it is concluded that the Asn-Gly processing site has been acquired rather than conserved during legumin gene evolution.