Lectin genes and their mature proteins: Still an exciting matter, as revealed by biochemistry and bioinformatics analyses of newly reported proteins

Two new lectins were purified through affinity chromatography after crude extract preparation under high ionic strength. The hemagglutinating activity of these lectins from the seeds of the legumes Dioclea bicolor (DBL) and Deguelia scandens (DSL) was inhibited by galactose and glucose, respectively, and the molecular masses were estimated at 24 and 22 kDa (via SDS-PAGE), respectively. The alignment of internal peptides of DBL (MS/MS) with known protein sequences revealed similarity to other legume lectins. The N-terminal amino acid sequence of DSL also aligned with legume lectins. Cross-similarities among the two studied lectins were observed only after sequence permutation. More than a dozen lectins have been reported for the genus Dioclea but none that recognize galactose. DSL is the first lectin reported for the Deguelia genus in the tribe Millettieae. With the aid of bioinformatics tools and searches for genome/transcriptome information about closely related sequences, new lectin members of Millettieae were also identified. Electrophoresis profiling and amino acid sequence analysis suggested that DBL-Gal and DSL do not undergo post-transcriptional ConA-like circular permutation. Molecular modeling of the deduced amino acid sequences of the Millettieae lectins suggested that the overall folding of the monomeric structures of legume lectins is conserved. This and other recent studies highlight native plants of the Amazon as renewed sources of lectins.