title: Do F-box proteins with a C-terminal domain homologous with the tobacco lectin play a role in protein degradation in plants?
abstract: Protein turnover is a key post-translational event that regulates numerous cellular processes. It enables cells to respond rapidly to intracellular signals and changing environmental conditions by adjusting the levels of pivotal proteins. A major proteolytic pathway involves the ubiquitination of target proteins and subsequent targeting to the 26S proteasome for degradation. Many F-box proteins play a determining role in the substrate specificity of this degradation pathway. In most cases, selective recognition of the target proteins relies on protein-protein interactions mediated by the C-terminal domain of the F-box proteins. In mammals, the occurrence of F-box proteins with a C-terminal SBD (sugar-binding domain) that specifically interacts with high-mannose N-glycans on target glycoproteins has been documented. The identification and characterization of these sugar-binding F-box proteins demonstrated that F-box proteins do not exclusively use protein-protein interactions but also protein-carbohydrate interactions in the Ub (ubiquitin)/proteasome pathway. Recently, putative sugar-binding F-box proteins have been identified in plants. Genome analyses in Arabidopsis and rice revealed the presence of F-box proteins with a C-terminal lectin-related domain homologous with Nictaba, a jasmonate-inducible lectin from tobacco that was shown to interact with the core structure of high-mannose and complex N-glycans. Owing to the high similarity in structure and specificity between Nictaba and the SBD of the mammalian Fbs proteins, a similar role for the plant F-box proteins with a Nictaba domain in nucleocytoplasmic protein degradation in plant cells is suggested.
authors.affiliation: Laboratory of Biochemistry and Glycobiology, Department of Molecular Biotechnology, Ghent University, Coupure Links 653, 9000 Ghent, Belgium.
authors.forename: Nausicaä
authors.initials: N
authors.lastname: Lannoo
authors.forename: Willy J
authors.initials: WJ
authors.lastname: Peumans
authors.forename: Els J M
authors.initials: EJ
authors.lastname: Van Damme
mesh_terms: D000818:Animals; D001483:Base Sequence; D044783:F-Box Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D037121:Plant Lectins / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D017434:Protein Structure, Tertiary; D044843:SKP Cullin F-Box Protein Ligases / Q000378:metabolism; D017422:Sequence Analysis, DNA; D013379:Substrate Specificity; D014026:Nicotiana / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism
chemical_list: D044783:F-Box Proteins; D037121:Plant Lectins; D010940:Plant Proteins; D025801:Ubiquitin; D044843:SKP Cullin F-Box Protein Ligases; D044767:Ubiquitin-Protein Ligases; D046988:Proteasome Endopeptidase Complex