title: The rub family of ubiquitin-like proteins. Crystal structure of Arabidopsis rub1 and expression of multiple rubs in Arabidopsis.
abstract: Several proteins with significant identity to ubiquitin have been characterized recently. In contrast to ubiquitin's main role in targeting proteins for degradation, a described function of one family of ubiquitin-related proteins, the Rub family, is to serve as a stable post-translational modification of a complex involved in the G1-to-S cell cycle transition. Rub proteins have been found in animals, plants, and fungi and consist of 76 residues with 52-63% identity to ubiquitin. In this study three different RUB proteins within the plant Arabidopsis are identified; two differ by only 1 amino acid, while the third is only 77.6% identical to the other two. Genes encoding all three are expressed in multiple organs. In addition, we report the crystal structure of higher plant RUB1 at 1.7-A resolution to help elucidate the functional differences between Rub and ubiquitin. RUB1 contains a single globular domain with a flexible COOH-terminal extension. The overall RUB1 structure is very similar to ubiquitin. The majority of the amino acid differences between RUB1 and ubiquitin map to the surface. These changes alter the electrostatic surface potential in two regions and likely confer specificity between ubiquitin and RUB1 and their ubiquitin-activating enzyme (E1) or E1-like activating enzymes.
authors.affiliation: Section of Molecular and Cellular Biology, University of California, Davis, California 95616, USA.
authors.forename: C
authors.initials: C
authors.lastname: Rao-Naik
authors.forename: W
authors.initials: W
authors.lastname: delaCruz
authors.forename: J M
authors.initials: JM
authors.lastname: Laplaza
authors.forename: S
authors.initials: S
authors.lastname: Tan
authors.forename: J
authors.initials: J
authors.lastname: Callis
authors.forename: A J
authors.initials: AJ
authors.lastname: Fisher
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis; D029681:Arabidopsis Proteins; D003461:Crystallography; D004926:Escherichia coli / Q000235:genetics; D017343:Genes, Plant; D008025:Ligases / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D011994:Recombinant Proteins / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D055672:Static Electricity; D013499:Surface Properties; D014018:Tissue Distribution; D044764:Ubiquitin-Activating Enzymes; D044767:Ubiquitin-Protein Ligases; D014452:Ubiquitins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D010940:Plant Proteins; C513170:RUB1 protein, Arabidopsis; D011994:Recombinant Proteins; D014452:Ubiquitins; D044767:Ubiquitin-Protein Ligases; D008025:Ligases; D044764:Ubiquitin-Activating Enzymes