Ubiquitin is a small regulatory protein found in most tissues of eukaryotic organisms, i.e., it is found ubiquitously. It was discovered in 1975 by Gideon Goldstein and further characterized throughout the late 1970s and 1980s. Four genes in the human genome code for ubiquitin: UBB, UBC, UBA52 and RPS27A.
Ubiquitin-like modifier activating enzyme 1 (UBA1) is an enzyme which in humans is encoded by the UBA1 gene. UBA1 participates in ubiquitination and the NEDD8 pathway for protein folding and degradation, among many other biological processes. This protein has been linked to X-linked spinal muscular atrophy type 2, neurodegenerative diseases, and cancers.
In molecular biology, SUMOproteins are a family of small proteins that are covalently attached to and detached from other proteins in cells to modify their function. This process is called SUMOylation. SUMOylation is a post-translational modification involved in various cellular processes, such as nuclear-cytosolic transport, transcriptional regulation, apoptosis, protein stability, response to stress, and progression through the cell cycle.
Ubiquitin-activating enzymes, also known as E1 enzymes, catalyze the first step in the ubiquitination reaction, which can target a protein for degradation via a proteasome. This covalent bond of ubiquitin or ubiquitin-like proteins to targeted proteins is a major mechanism for regulating protein function in eukaryotic organisms. Many processes such as cell division, immune responses and embryonic development are also regulated by post-translational modification by ubiquitin and ubiquitin-like proteins.
SUMO enzymatic cascade catalyzes the dynamic posttranslational modification process of sumoylation. The Small Ubiquitin-related Modifier, SUMO-1, is a ubiquitin-like family member that is conjugated to its substrates through three discrete enzymatic steps : activation, involving the E1 enzyme (SAE1/SAE2); conjugation, involving the E2 enzyme (UBE2I); substrate modification, through the cooperation of the E2 and E3 protein ligases.
Histone-modifying enzymes are enzymes involved in the modification of histone substrates after protein translation and affect cellular processes including gene expression. To safely store the eukaryotic genome, DNA is wrapped around four core histone proteins, which then join to form nucleosomes. These nucleosomes further fold together into highly condensed chromatin, which renders the organism's genetic material far less accessible to the factors required for gene transcription, DNA replication, recombination and repair. Subsequently, eukaryotic organisms have developed intricate mechanisms to overcome this repressive barrier imposed by the chromatin through histone modification, a type of post-translational modification which typically involves covalently attaching certain groups to histone residues. Once added to the histone, these groups elicit either a loose and open histone conformation, euchromatin, or a tight and closed histone conformation, heterochromatin. Euchromatin marks active transcription and gene expression, as the light packing of histones in this way allows entry for proteins involved in the transcription process. As such, the tightly packed heterochromatin marks the absence of current gene expression.
Small ubiquitin-related modifier 1 is a protein that in humans is encoded by the SUMO1 gene.
SUMO-conjugating enzyme UBC9 is an enzyme that in humans is encoded by the UBE2I gene. It is also sometimes referred to as "ubiquitin conjugating enzyme E2I" or "ubiquitin carrier protein 9", even though these names do not accurately describe its function.
Small ubiquitin-related modifier 2 is a protein that in humans is encoded by the SUMO2 gene.
Ran GTPase-activating protein 1 is an enzyme that in humans is encoded by the RANGAP1 gene.
Small ubiquitin-related modifier 3 is a protein that in humans is encoded by the SUMO3 gene.
Ubiquitin-conjugating enzyme E2 N is a protein that in humans is encoded by the UBE2N gene.
SUMO-activating enzyme subunit 1 is a protein that in humans is encoded by the SAE1 gene.
Ubiquitin-conjugating enzyme E2 variant 2 is a protein that in humans is encoded by the UBE2V2 gene. Ubiquitin-conjugating enzyme E2 variant proteins constitute a distinct subfamily within the E2 protein family.
NEDD8-activating enzyme E1 regulatory subunit is a protein that in humans is encoded by the NAE1 gene.
NEDD8-activating enzyme E1 catalytic subunit is a protein that in humans is encoded by the UBA3 gene.
Ubiquitin-conjugating enzyme E2 E3 is a protein that in humans is encoded by the UBE2E3 gene.
NEDD8-conjugating enzyme Ubc12 is a protein that in humans is encoded by the UBE2M gene.
Ubiquitin-fold modifier 1, also known as UFM1, is a protein which in humans is encoded by the UFM1 gene.
Arabidopsis SUMO-conjugation enzyme (AtSCE1) is an enzyme that is a member of the small ubiquitin-like modifier (SUMO) post-translational modification pathway. This process, and the SCE1 enzyme with it, is highly conserved across eukaryotes yet absent in prokaryotes. In short, this pathway results in the attachment of a small polypeptide through an isopeptide bond between modifying enzyme and the ε-amino group of a lysine residue in the substrate. In plants, the 160 amino acid SCE1 enzyme was first characterized in 2003. One functional gene copy, SCE1a, was found on chromosomes 3.
