Ubiquitin

RPS27A is a small protein composed of 76 amino acids. RPS27A is found only in eukaryotic organisms among which shows strong sequence conservation. The RPS27A protein is present in all cell types, thus giving rise to its name.
RPS27A is found either in free form or conjugated to proteins through a covalent bond between the glycine at the C-terminal end and the side chains of lysine.
The connection of multiple copies of RPS27A targets the proteins for degradation by the 26S proteosome. RPS27A ligation is an ATP-dependent multi-step process. RPS27A is activated by the E1 enzyme. The attachment of RPS27A to the target protein is catalyzed by the E2 enzyme acting in concert with E3 which is involved in the recognition of the substrate protein.

USP46 is a part of a large family of cysteine proteases that function as deubiquitinating enzymes which interacts with WDR48 to have a high activity. USP46 operates by mediating the deubiquitination of GAD1/GAD67.

USP15 belongs to the ubiquitin specific protease (USP) family of deubiquitinating enzymes which has a vital role in ubiquitin-dependent processes through polyubiquitin chain disassembly and hydrolysis of ubiquitin-substrate bonds. USP15 connects with the COP9 signalosome, and takes part in transforming growth factor beta signalling through deubiquitination of receptor-activated SMAD transcription factors. Alternatively spliced transcript variants encoding multiple isoforms of this gene are known, and a pseudo gene of USP15 is sited on the long arm of chromosome 2.

USP14 belongs to the ubiquitin-specific processing (UBP) family of proteases which is a deubiquitinating enzyme (DUB) containing His and Cys domains. USP14 placed in the cytoplasm and cuts the ubiquitin from ubiquitin-fused precursors and ubiquitinylated proteins.a mutation which results in reduced expression of the ortholog of USP14 in mice inhibits growth, develop severe tremors by 2 to 3 weeks of age followed by paralysis and death by 6 to 10 weeks of age.

URM1 is ubiquitin-related modifier 1 homolog protein which mainly functions in the post-translational modification of proteins via the urmylation pathway. Urm1 covalently binds to its E1 activating enzyme, Uba4p, to conjugate alkyl hydroperoxide reductase (Ahp1) as determined by studies with Saccharomyces cerevisiae. It has been theorized that this complex may then have a role in the oxidative-stress response in mammals.

UFM1 is a ubiquitin-like protein which is conjugated to target proteins by E1-like activating enzyme UBA5 and E2-like conjugating enzyme UFC1 in a manner equivalent to ubiquitylation. UFM1 localizes principally to the nucleus, but is also present in diffuse amounts in the cytoplasm. UFM1 is expressed in a variety of tissues, including kidney, brain, heart, liver and lung.

Ubiquilin-2, also known as UBQLN2 contains an N-terminal ubiquitin-like domain and a C-terminal ubiquitin-associated domain. UBQLN2 is physically linked with proteasomes as well as ubiquitin ligases, and therefore is considered to functionally connect the ubiquitination machinery to the proteasome in order to affect in vivo protein degradation. Furthermore, UBQLN2 binds the ATPase domain of the Hsp70-like Stch protein. Among the diseases which are associated with UBQLN2: Amyotrophic lateral sclerosis 15, with or without frontotemporal dementia as well as Amyotrophic lateral sclerosis type 15.

Ubiquitin-like domain-containing CTD phosphatase 1 (UBLCP1) dephosphorylates 26S nuclear proteasomes, thereby decreasing their proteolytic activity. The dephosphorylation averts assembly of the core and regulatory particles (CP and RP) into mature 26S proteasome.

UBL5 is believed to be a reversible modulator of protein function unlike ubiquitin which is a protein degrader. UBL5 influences a nuclear phase obligatory for increasing a reaction against the risk of mitochondrial protein misfolding.

Ubiquitin-Like 4A (UBL4A) contains one ubiquitin-like domain. UBL4A is a component of the BAT3 complex, which is a multiprotein complex involved in the post-translational delivery of tail-anchored (TA) membrane proteins to the endoplasmic reticulum membrane. Post-translational modification by ubiquitin and ubiquitin-related proteins plays decisive roles in protein degradation and in regulation of crucial cellular processes. Due to the fact that in mammals, transcription halts during late spermiogenesis as a result of compaction of the spermatid genome, which creates a special need for robust post-transcriptional regulation.

UBL3 - a member of the ubiquitin-like family is found in the membrane. UBL3 holds two N-glycosylation sites, a C-terminal prenylation site and a protein kinase C phosphorylation site. Even though Ubiquitin-like proteins are not directly involved in protein degradation, it seems they have several mechanistic similarities to the ubiquitin pathway.

Ubiquitin is a highly conserved 76 amino acid protein expressed in all eukariotes. Ub is found either in free form or conjugated to proteins as monomer or as chain of ubiquitin molecules. The most well characterized consequence of polyubiquitination is substrate degradation, while mono-ubiquitinated proteins are not degraded. Ubiquitin attachment to protein substrate is a complex process involving a ubiquitin activating enzyme (E1), a ubiquitin conjugating enzyme (E2) and a ubiquitin protein ligase (E3). The first ubiquitin moiety is transferred to the e-NH2 group of a Lys residue of the protein substrate to generate an isopeptide bond. In successive reactions, a poly ubiquitin chain is synthesized by processive transfer of additional activated moieties to Lys48 of the previously conjugated ubiquitin molecule. Ubiquitin K48R prevents the formation of poly ubiquitin chains via Lys48 linkages with mono ubiquitin molecules, avoiding the degradation of protein substrates.

The conserved 76 amino acid protein ubiquitin (Ub) regulates a host of intracellular processes through its enzymatic conjugation to other cellular proteins.
Ubiquitination occurs through sequential steps catalyzed by activating (E1), conjugating (E2), and ligase (E3) enzymes. The final step results in the formation of an isopeptide bond between Ub’s C-terminal glycine residue (G76) and a lysine residue of the target protein, although N-terminal ubiquitination is also known.
Outcomes of this modification include destabilization of the conjugated protein, altered protein trafficking and functional modulation.
After targeting the protein for specific localizations, ubiquitin is released from the substrate by deubiquitinating enzymes.
A mutant ubiquitin, having a Gly to Ala substitution at the C-terminus (G76A ubiquitin) supported several downstream reactions of the proteolytic pathway but inhibits the deubiquitination process.
As consequence, the Ub derivative becomes irreversibly conjugated to protein, shifting the equilibrium between the bound and unbound form in the direction of conjugation, at the expense of the free form.

Ubiquitin D (UBD) is an ubiquitin-like modifier (UBL) of the ubiquitin protein family. UBD is an ubiquitin-like protein which can form covalent conjugates, thus targeting proteins for degradation by the 26S proteasome. It is assumed that, UBD has roles in regulation of cell cycle, innate immunity, and apoptosis. UBD is a TNF-a inducible ubiquitin-like protein with a presumed role in the immune response.

ISG15 ubiquitin-like Modifier is conjugated to the intracellular target proteins after IFN-alpha or IFN-beta stimulation. ISG15 enzymatic pathway is partially distinct from that of ubiquitin, differing in substrate specificity and interaction with ligating enzymes. ISG15 conjugation pathway uses a dedicated E1 enzyme, but seems to converge with the ub conjugation pathway at the level of a specific E2 enzyme. ISG15 protein targets include STAT1, SERPINA 3G/SPI2A, JAK1, MAPK3/ERK1, PLCG1, EIF2AK2/PKR, MX1/MXA, and RIG-1. Deconjugated by USP18/UBP43 shows specific chemotactic activity towards neutrophils and activates them to induce release of eosinophil chemotactic factors. ISG15 serves as a trans-acting binding factor directing the association of ligated target proteins to intermediate filaments. ISG15 plays a role in autocrine, paracrine and endocrine mechanisms, as in cell-to-cell signaling, possibly partly by inducing ifn-gamma secretion by monocytes and macrophages. ISG15 displays antiviral activity during viral infections. ISG15 in response to IFN-TAU secreted by the conceptus, ligates to and regulate proteins involved in the release of prostaglandin F2-alpha and thus prevent lysis of the corpus luteum and maintain the pregnancy. ISG15 shares several common properties with other ubiquitin-like molecules, but its activity is strongly regulated by precise signaling pathways that have a role in innate immunity.

SUMO3 belongs to the SUMO protein family and operates like ubiquitin. Nevertheless, unlike ubiquitin that targets proteins for degradation, SUMO3 protein takes part in several cellular processes, like nuclear transport, transcriptional regulation, apoptosis, and protein stability. SUMO3 regulates amyloid beta generation and is crucial in the onset or progression of Alzheimer’s disease.

Small Ubiquitin-like Modifiers (SUMOs) are a family of small, related proteins that can be enzymatically attached to a target protein by a post-translational modification process termed sumoylation. Unlike ubiquitination, which targets proteins for degradation, sumoylation participates in a number of cellular processes, such as nuclear transport, transcriptional regulation, apoptosis, and protein stability. All SUMO proteins share the conserved ubiquitin domain and the C-terminal diglycine cleavage/attachment site. Human SUMO2, also known as Sentrin2 and SMT3B is synthesized as a 95 amino acid (aa), 11 kDa propeptide that contains a two aa C-terminal prosegment, and an 18 aa N-terminal protein interacting region (aa 33 -50). Following prosegment cleavage, the C-terminal glycine is enzymatically attached to a lysine on a target protein. Human SUMO2 shares 100% sequence identity to SUMO-2 from mouse. SUMO2 also has very high sequence homology to SUMO3 and SUMO4, 86 % and 85%, respectively. SUMO2 shares only 44% sequence identity to SUMO1.

SUMO1 is a protein that belongs to the SUMO (small ubiquitin-like modifier) protein family. SUMO1 functions in a manner similar to ubiquitin in that it is bound to target proteins as part of a post-translational modification system. Still, unlike ubiquitin which targets proteins for degradation, SUMO1 is involved in a variety of cellular processes, for example nuclear transport, transcriptional regulation, apoptosis, and protein stability. SUMO1 is not active until the last four amino acids of the carboxy-terminus are cleaved off.

SUMO1 is a protein that belongs to the SUMO (small ubiquitin-like modifier) protein family. SUMO1 functions in a manner similar to ubiquitin in that it is bound to target proteins as part of a post-translational modification system. Still, unlike ubiquitin which targets proteins for degradation, SUMO1 is involved in a variety of cellular processes, for example nuclear transport, transcriptional regulation, apoptosis, and protein stability. SUMO1 is not active until the last four amino acids of the carboxy-terminus are cleaved off.

Ubiquitin thioesterase OTUB2 (OTUB2) is a member of the peptidase C65 family. OTUB2 functions as a hydrolase which can remove conjugated ubiquitin from proteins in vitro and may thus play a key regulatory role at the level of protein turnover by preventing degradation.

Otubain 1 (OTUB1) belongs to the ovarian tumor (OUT) superfamily of predicted cysteine proteases and inhibits cytokine gene transcription in the immune system through its interaction with a ubiquitin protease and E3 ubiquitin ligase. OTUB1 is a highly specific ubiquitin iso-peptidase, it cleaves ubiquitin from branched poly-ubiquitin chains but not from ubiquitinated substrates. OTUB1 is believed to work in specific ubiquitin-dependent pathways, possibly by providing an editing function of polyubiquitin chain growth. OTUB1 is a hydrolase that removes conjugated ubiquitin from proteins in vitro and may therefore have a significant regulatory role in the level of protein turnover by preventing degradation. Additionally, OTUB1 is a regulator of T-cell anergy, a phenomenon that occurs when T-cells are rendered impassive to antigen re-challenge and no longer respond to their cognate antigen. OTUB1 acts via its interaction with RNF128/GRAIL, which is an essential inductor of CD4 T-cell anergy.

Recombinant Human Ubiquitin having the accession number of P62988 was conjugated to Biotin. RPS27A is a small protein composed of 76 amino acids. RPS27A is found only in eukaryotic organisms among which shows strong sequence conservation. The RPS27A protein is present in all cell types, thus giving rise to its name.
RPS27A is found either in free form or conjugated to proteins through a covalent bond between the glycine at the C-terminal end and the side chains of lysine.
The connection of multiple copies of RPS27A targets the proteins for degradation by the 26S proteosome. RPS27A ligation is an ATP-dependent multi-step process. RPS27A is activated by the E1 enzyme. The attachment of RPS27A to the target protein is catalyzed by the E2 enzyme acting in concert with E3 which is involved in the recognition of the substrate protein.