cDNA molecular cloning and seasonal acumulation of an ebulin 1-related dimeric lectin of dwarf elder (Sambucus ebulus L.) leaves

SEL1d is a dimeric D-galactose and mucin-binding lectin (apparent Mr 68,000) which coexists with the non-toxic type 2 ribosome-inactivating protein (RIP) ebulin 1 in dwarf elder (Sambucus ebulus L.) leaves. To ascertain a potential structural correlation with ebulin 1 molecular cloning of a cDNA coding for SEL1d was performed. SEL1d shared a 76% of identity with the ebulin 1-B chain. Notably, it was found that SEL1d has Tyr present in the high affinity 2gamma sugar-binding domain of ricin which is absent in ebulin 1-B chain and which seems responsible of the low cell and in vivo toxicities of ebulin 1. The concentration of ebulin 1 in leaves decreased along the developmental stage of dwarf elder and almost disappeared in senescence while the content in SEL1d changed in the opposite way. Our results suggest that SEL1d and ebulin 1 play different biological roles in dwarf elder leaves. (C) 2003 Elsevier Science Ltd. All rights reserved.