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STRUCTURE OF UBIQUITIN-LIKE PROTEIN, RUB1
Structural highlights
FunctionRUB1_ARATH Ubiquitin exists either covalently attached to another protein, or free (unanchored). When covalently bound, it is conjugated to target proteins via an isopeptide bond either as a monomer (monoubiquitin), a polymer linked via different Lys residues of the ubiquitin (polyubiquitin chains) or a linear polymer linked via the initiator Met of the ubiquitin (linear polyubiquitin chains). Polyubiquitin chains, when attached to a target protein, have different functions depending on the Lys residue of the ubiquitin that is linked: Lys-11-linked is involved in ERAD (endoplasmic reticulum-associated degradation) and in cell-cycle regulation; Lys-29-linked is involved in lysosomal degradation; Lys-33-linked is involved in kinase modification; Lys-48-linked is involved in protein degradation via the proteasome; Lys-63-linked is involved in endocytosis, and DNA-damage responses. Linear polymer chains formed via attachment by the initiator Met lead to cell signaling. Ubiquitin is usually conjugated to Lys residues of target proteins, however, in rare cases, conjugation to Cys or Ser residues has been observed. When polyubiquitin is free (unanchored-polyubiquitin), it also has distinct roles, such as in activation of protein kinases, and in signaling (By similarity).[1] [2] NEDD8-like protein RUB1: Appears to function as a stable post-translational protein modifier. An AMP-RUB1 intermediate is formed by an activating enzyme, distinct from the ubiquitin activating enzyme E1, which is composed of a heterodimer AXR1/ECR1. Auxin response is mediated, at least in part, through modification of the cullin AtCUL1 by the attachment of RUB1 to 'Lys-692'.[3] [4] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedSeveral 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. The rub family of ubiquitin-like proteins. Crystal structure of Arabidopsis rub1 and expression of multiple rubs in Arabidopsis.,Rao-Naik C, delaCruz W, Laplaza JM, Tan S, Callis J, Fisher AJ J Biol Chem. 1998 Dec 25;273(52):34976-82. PMID:9857029[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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