The NeuAc(α-2,6)-Gal/GalNAc-binding lectin from elderberry (Sambucus nigra) bark, a type-2 ribosome-inactivating protein with an unusual specificity and structure

Abstract

The cDNA encoding the NeuAc(α-2,6)Gal/GalNAc binding lectin from elderberry (Sambucus nigra) bark (SNAI) was isolated from a cDNA library constructed with mRNA from the bark. Sequence analysis of this lectin cDNA revealed a striking similarity to the previously sequenced type-2 ribosome-inactivating proteins from Ricinus communis and Abrus precatorius. Molecular modelling of SNAI further indicated that its structure closely resembles that of ricin. Since SNAI strongly inhibits cell-free protein synthesis in a rabbit reticulocyte lysale it presumably is a type-2 ribosome-inactivating protein. However, SNAI differs from all previously described type-2 ribosome-inactivating proteins by its specificity towards NeuAc(α-2,6)Gal/GalNAc and its unusual molecular structure.