The “Old” Euonymus europaeus Agglutinin Represents a Novel Family of Ubiquitous Plant Proteins    

Abstract

Molecular cloning of the “old” but still unclassified Euonymus europaeus agglutinin (EEA) demonstrated that the lectin is a homodimeric protein composed of 152 residue subunits. Analysis of the deduced sequence indicated that EEA is synthesized without a signal peptide and undergoes no posttranslational processing apart from the removal of a six-residue N-terminal peptide. Glycan array screening confirmed the previously reported high reactivity of EEA toward blood group B oligosaccharides but also revealed binding to high mannose N-glycans, providing firm evidence for the occurrence of a plant carbohydrate-binding domain that can interact with structurally different glycans. Basic Local Alignment Search Tool searches indicated that EEA shares no detectable sequence similarity with any other lectin but is closely related evolutionarily to a domain that was first identified in some abscisic acid- and salt stress-responsive rice (Oryza sativa) proteins, and, according to the available sequence data, might be ubiquitous in Spermatophyta. Hence, EEA can be considered the prototype of a novel family of presumably cytoplasmic/nuclear proteins that are apparently ubiquitous in plants. Taking into account that some of these proteins are definitely stress related, the present identification of the EEA lectin domain might be a first step in the recognition of the involvement and importance of protein-glycoconjugate interactions in some essential cellular processes in Embryophyta.

Combined Proteomic and Cytological Analysis of Ca2+-Calmodulin Regulation inPicea meyeriPollen Tube Growth

“…We can safely conclude that the dramatically elevated Ca 2+ concentrations in the cytoplasm correlated well with the strong down-regulation of calreticulins (spots 1 and 48). In addition, the newly identified Hyp-rich glycoprotein (spot E17) is a stressresponsive lectin-like protein that contains a QXW lectin repeat domain, which might be a first step in the recognition of the involvement and importance of proteinglycoconjugate interactions in some essential cellular processes Fouquaert et al, 2008).…”

Characterization of a type D1A EUL-related lectin from rice expressed in Pichia pastoris

“…Of particular interest are the Euonymus lectin sequences, which are present in all sequenced genomes. The Euonymus europaeus agglutinin (EEA) was cloned a few years ago (Fouquaert et al, 2008). As then EEA has become the prototype of a new family of proteins referred to as the Euonymus lectin-related (EUL) family, grouping all proteins with one or more EUL-related sequences.…”

“…As then EEA has become the prototype of a new family of proteins referred to as the Euonymus lectin-related (EUL) family, grouping all proteins with one or more EUL-related sequences. In silico screening of available genomes and transcriptomes revealed that the EUL family is omnipresent in the plant kingdom (Fouquaert et al, 2008). Based on the architecture of the EUL domain identified in different protein sequences, a classification system was elaborated (Fouquaert et al, 2009a).…”

Lectin activity of the nucleocytoplasmic EUL protein from Arabidopsis thaliana

“…In 2008 the molecular cloning of the Euonymus europaeus agglutinin (EEA) from spindle tree led to the discovery of a new family of lectins [3]. Since then the Euonymus lectin domain (EUL) is considered as the structural unit of a novel family of putative carbohydrate-binding proteins.…”

“…An extensive screening of publicly accessible genome databases revealed that the EUL domain is widespread among green plants [3]. Furthermore some sequences consist of a single EUL domain linked to an unrelated N-terminal domain whereas others comprise two in tandem arrayed EUL domains.…”