Ubiquitin Conjugating Enzyme

Protein Tyrosine Phosphatase Receptor Type N (PTPRN) is a catalytically inactive protein and a major target of autoimmune response in diabetes mellitus. The long C-terminal intracellular tail covers the majority of autoantibody epitopes. PTPRN is expressed in neural, neuroendocrine and pancreatic islet cells.

UFC1 is a member of the ubiquitin-conjugating enzyme family. UFC1 is an E2-like conjugating enzyme for ubiquitin-fold modifier-1. UFM1 is activated by UBA5 (a novel E1-like enzyme) by forming a high-energy thioester bond. Activated UFM1 is subsequently transferred to its cognate E2-like enzyme, UFC1, in a similar thioester linkage.

UCHL5 is a member of the peptidase C12 family. UCHL5 protein is a protease that specifically cleaves 'Lys-48'-linked polyubiquitin chains, and deubiquitinating enzyme related to the 19S regulatory subunit of the 26S proteasome.

Ubiquitin carboxyl-terminal hydrolase isozyme L3 belongs to a gene family whose products hydrolyze small C-terminal adducts of ubiquitin to produce the ubiquitin monomer. UCHL3 takes part in the regulation of neuronal development and spermatogenesis and is associated to neurodegenerative diseases. UCHL3 has a 54% homology to UCHL1.

Ubiquitin carboxyl-terminal hydrolase isozyme L3 belongs to a gene family whose products hydrolyze small C-terminal adducts of ubiquitin to produce the ubiquitin monomer. UCHL3 takes part in the regulation of neuronal development and spermatogenesis and is associated to neurodegenerative diseases. UCHL3 has a 54% homology to UCHL1.

Ubiquitin Conjugating Enzyme E2Z, also known as UBE2z, is a protein coding gene which is a part of the ubiquitin-conjugating enzyme family. UBE2z catalyzes the covalent attachment of ubiquitin to various proteins. UBE2z takes part in in apoptosis regulation and is also a specific substrate for UBA6, not charged with ubiquitin by UBE1.

UBE2W receives ubiquitin from the E1 complex and catalyzes its covalent attachment to other proteins. In vitro, UBE2W catalyzes monoubiquitination and 'Lys-11'-linked polyubiquitination. UBE2W is broadly expressed, particularly at highest levels in the testis.

UBE2V2 comprises a distinct subfamily within the E2 protein family. They have sequence similarity to other ubiquitin-conjugating enzymes however require the conserved cysteine residue that is vital for the catalytic activity of E2s. UBE2V2 shares homology with ubiquitin-conjugating enzyme E2 variant 1 and yeast MMS2 gene product. UBE2V2 participates in the differentiation of monocytes and enterocytes.

UBE2T is part of the E2 ubiquitin-conjugating enzyme family that participates in the protein degradation pathway. UBE2T catalyzes the ATP-dependent attachment of ubiquitin to target proteins, thus tagging them for subsequent destruction by the proteasome. UBE2T is an important factor of the Faconi anemia pathway of DNA damage repair and, upon self-inactivation, may negatively regulate the Faconi pathway.

Ubiquitin-conjugating enzyme E2S (UBE2S) belongs to the ubiquitin-conjugating enzyme family. UBE2S is able to form a thiol ester linkage with ubiquitin in a ubiquitin activating enzyme-dependent manner, a typical property of ubiquitin carrier proteins. UBE2S catalyzes the covalent attachment of ubiquitin to other proteins. UBE2S acts as a crucial factor of the anaphase promoting complex/cyclosome (APC/C), which is a cell cycle-regulated ubiquitin ligase that controls progression through mitosis. UBE2S acts by purposely elongating 'Lys-11'-linked polyubiquitin chains initiated by the E2 enzyme UBE2C/UBCH10 on APC/C substrates, augmenting the degradation of APC/C substrates by the proteasome and promoting mitotic exit. UBE2S also acts by elongating ubiquitin chains initiated by the E2 enzyme UBE2D1/UBCH5 in vitro; it is nevertheless uncertain whether UBE2D1/UBCH5 acts as an E2 enzyme for the APC/C in vivo. UBE2S is also involved in ubiquitination and consequent degradation of VHL, resulting in an accumulation of HIF1A.

Ubiquitin-conjugating enzyme E2 R2 (UBE2R2) is a member of the ubiquitin-conjugating enzyme family. Protein kinase CK2 is a ubiquitous and pleiotropic Ser/Thr protein kinase implicated in cell growth andtransformation. This protein is a protein similar to the E2 ubiquitin conjugating enzyme UBC3/CDC34. Studies propose that CK2-dependent phosphorylation of this ubiquitin-conjugating enzyme functions by regulating beta-TrCP substrate recognition and induces its interaction with beta-TrCP, enhancing beta-catenin degradation. UBE2R2 receives ubiquitin from the E1 complex and catalyzes its covalent attachment to other proteins. In vitro catalyzes monoubiquitination and 'Lys-48'-linked polyubiquitination. UBE2R2 may be implicated in degradation of katenin. Among the diseases associated with UBE2R2 are cblc, and herpes simplex.

Ubiquitin Conjugating Enzyme E2Q2 (UBE2Q2) is a protein coding gene which receives ubiquitin from the E1 complex and catalyzes its covalent attachment to various proteins. UBE2Q2 which is a part of the ubiquitin-conjugating enzyme family is detected in hypopharyngeal head and neck squamous cell carcinoma and in tumor masses.

UBE2N belongs to the E2 ubiquitin-conjugating enzyme family. UBE2N catalyzes the ATP-dependent synthesis of non-canonical polyubiquitin chains, a process which doesn’t set in motion proteasomal degradation. UBE2N mediates the transcription of some target genes and is believed to have a role in cell cycle progression; cellular differentiation and DNA repair mechanisms which ensure cell survival after DNA damage.

UbcH12 is functional in in vitro NEDDylation reactions. It has been shown to form a thioester linkage with NEDD8 in the presence of the NEDD8 activating enzyme complex Uba3/APP-BP1. APP-BP1 binds to the amyloid precursor protein (APP) carboxy terminal domain and is important in conjunction with Uba3 and UbcH12 in driving cells through the S to M checkpoint. It was demonstrated to be the E2 responsible for the NEDDylation of the Cul-1 component of the SCF (?-TRCP) complex which is important as the E3-ligase in the ubiquitinylation of I?B?. NEDDylation of Cul-1 is essential for conjugation and processing of NF-?B p105 by SCF (?-TRCP) following phosphorylation of the complex. A dominant negative form of UbcH12, previously demonstrated to sequester NEDD8 and inhibit its conjugation, inhibits both conjugation and processing of p105, which is alleviated by wild-type UbcH12.

UBE2L6 belongs to the E2 ubiquitin-conjugating enzyme family. UBE2L6 enzyme is very similar in its primary structure to the enzyme encoded by UBE2L3 gene. UBE2L6 catalyzes the covalent attachment of ubiquitin to other proteins. UBE2L6 functions in the e6/e6-ap-induced ubiquitination of p53/tp53.

Human Ubquitin Conjugating Enzyme 7 (UbcH7) is a class I enzyme which functions in the stress response and the control of transcription factors. The enzyme is ubiquitously expressed with high levels of expression seen in adult muscle. UbcH7 mediates the selective degradation of short-lived and abnormal proteins and is highly homologous to UbcH5. It has been demonstrated to participate in the ubiquitinylation of p53, c-Fos and NF-?B. UbcH7 is one of two E2s (UbcH5 being the other) with which HECT domain proteins interact with UbcH7 being able to efficiently substitute for UbcH5 in E6-AP-dependent ubiquitinylation.

Human Ubquitin-conjugating enzyme 7 (UbcH7) is a ubiquitin-conjugating enzyme (E2) mediating c-fos degradation, transcription factor NF-B maturation, and human papilloma virus-mediated p53 and Myc protein degradation, in vitro. The ubiquitin-conjugating enzymes (E2s) are essential components of the post-translational protein ubiquitination pathway, mediating the transfer of activated ubiquitin to substrate proteins. The human UBE2L1-UBE2L4 gene could potentially encode different isoforms of the UbcH7. UBE2L3 gene, located at chromosome 22q11.2, is the only identical family member with introns and encodes a polypeptide sequence identical to that of UbcH7.

UBE2K belongs to the ubiquitin-conjugating enzymes family which take part in many cellular processes such as selective protein degradation, DNA repair, cell cycle control, and sporulation. In this mechanism, the ATP-coupled activation and subsequent ligation of ubiquitin are catalyzed by separate enzymes functionally linked by ubiquitin carrier protein UBC1. In addition, UBE2K is involved in Alzheimer's disease, Huntington's disease and antigen processing through its interaction with amyloid-?, huntingtin, and MHC-heavy chain proteins.

Ubiquitin-conjugating enzyme E2 J2 (UBE2J2) is a member of the ubiquitin-conjugating enzyme family. UBE2J2 catalyzes the covalent attachment of ubiquitin to other proteins. UBE2J2 is located in the membrane of the endoplasmic reticulum. UBE2J2 participates in the selective degradation of misfolded membrane proteins from the endoplasmic reticulum (ERAD).

Human Ubquitin Conjugating Enzyme 9 (Ubc9) is a member of the E2 family and is specific for the conjugation of SUMO to a variety of target proteins. SUMO conjugation to target proteins is mediated by a different, but analogous, pathway to ubiquitinylation. This E2 is unusual in that it interacts directly with protein substrates that are modified by sumolyation, and may play a role in substrate recognition. Ubc9 can mediate the conjugation of SUMO-1 to a variety of proteins including RanGAP1, I?B?, and PML without the requirement of an E3 ligase.

Human Ubc9 is homologous to ubiquitin-conjugating enzymes (E2s). However, instead of conjugating ubiquitin, it conjugates a ubiquitin homologue, small ubiquitin-like modifier 1(SUMO-1). And hUbc9 retains striking structural and functional conservation with yeast Ubc9. The ubiquitin-dependent protein degradation system has been recognized as a complete enzymatic pathway that is responsible for the selective degradation of abnormal and short-lived proteins. The conjugation of ubiquitin requires the activities of ubiquitin-activating (E1) and –conjugating (E2) enzymes.

Ubiquitin-conjugating enzyme E2 H (UBE2H) is a member of the ubiquitin-conjugating enzyme family. Protein modification with ubiquitin is a vital cellular apparatus for directing abnormal or short-lived proteins for degradation. Ubiquitination requires at least 3 classes of enzymes: ubiquitin-activating enzymes (E1s) ubiquitin-conjugating enzymes (E2s) and ubiquitin-protein ligases (E3s). UBE2H receives ubiquitin from the E1 complex and catalyzes its covalent attachment to other proteins. UBE2H protein sequence is 100% identical to the mouse homolog and 98% identical to the frog and zebrafish homologs.

Ubiquitin-Conjugating Enzyme E2G2 (UBE2G2) is a protein coding gene which is a part of the E2 ubiquitin-conjugating enzyme family. UBE2G2 accepts ubiquitin from the E1 complex and catalyzes its covalent attachment to various proteins. UBE2G2 is ubiquitously expressed mainly in adult muscle. UBE2G2 also takes part in endoplasmic reticulum-associated degradation (ERAD).

Protein modification with ubiquitin is an essential cellular mechanism for targeting abnormal or short-lived proteins for degradation. Ubiquitination involves at least 3 classes of enzymes: ubiquitin-activating enzymes (E1s) ubiquitin-conjugating enzymes (E2s) and ubiquitin-protein ligases (E3s). Ubiquitin-Conjugating Enzyme E2G (UBE2G1) belongs to the E2 ubiquitin-conjugating enzyme family and catalyzes the covalent attachment of ubiquitin to other proteins. UE2G1 protein is involved in degradation of muscle-specific proteins.

Ubiquitin-conjugating enzyme E2 F (UBE2F) is a member of the ubiquitin-conjugating enzyme family and UBE2F subfamily. Ubiquitin-conjugating enzymes or sometimes as ubiquitin-carrier enzymes, run the second step in the ubiquitination reaction which targets a protein for degradation using the proteasome. The UBE2F receives the ubiquitin-like protein NEDD8 from the UBA3-NAE1 E1 complex and catalyzes its covalent attachment to other proteins.
RBX2-UBE2F complex neddylates specific target proteins, for example CUL5 as can be seen from the specific interaction with the E3 ubiquitin ligase RBX2, but not RBX1.

UBE2E3 or Ubiquitin-conjugating enzyme E2 E3 is part of the E2 ubiquitinconjugating enzyme family. UBE2E3 is needed for the destruction of mitotic cyclins and for cell cycle progression. The ubiquitination process covalently attaches to a short protein of 76 amino acids called ubiquitin, to a lysine residue on the target protein. When a protein has been tagged with one ubiquitin molecule, other rounds of ubiquitination form a polyubiquitin chain that is recognized by the proteasome's 19S regulatory particle, triggering the ATP-dependent unfolding of the target protein which grants passage into the proteasome's 20S core particle, where proteases degrade the target into short peptide fragments for recycling by the cell.

UBE2E1 belongs to the E2 ubiquitin-conjugating enzyme family. UBE2E1 accepts ubiquitin from the E1 complex and catalyzes its covalent attachment to other proteins. UBE2E1 catalyzes the covalent attachment of ISG15 to other proteins. UBE2E1 mediates the selective degradation of short-lived and abnormal proteins. In vitro, UBE2E1 also catalyzes 'Lys-48'-linked polyubiquitination.

UBE2D4 is a member of the ubiquitin-conjugating enzyme family. Ubiquitin-conjugating enzymes (E2 enzymes or ubiquitin-carrier enzymes) execute the second step in the ubiquitination reaction which marks a protein for degradation using the proteasome. UBE2D4 receives ubiquitin from the E1 complex and catalyzes its covalent attachment to other proteins. In vitro UBE2D4 can promote polyubiquitination using all 7 ubiquitin Lys residues, but usually selects 'Lys-11' and 'Lys-48'-linked polyubiquitination.

UBE2D3 enzymes are human homologs of the yeast UBC4/5 family and play many important regulatory roles in inflammation and cancer. UbcH5a mediates the degradation of a myriad of short-lived regulatory proteins (such as p53 in the presence of E6/E6-AP or MDM2, c-Fos, I?B?, p105) and abnormal proteins. UBE2D3 has 88% and 89% sequence identity with UbcH5a and UbcH5b respectively.

UBE2D2 belongs to the E2 ubiquitin-conjugating enzyme family. UBE2D2 takes part in the ubiquitination of the tumor-suppressor protein p53, which is induced by an E3 ubiquitin-protein ligase. UBE2D2 catalyzes ubiquitination of IkB-alpha in a SCFB-TRCP and phosphorylation dependent method.

UBE2D2 belongs to the E2 ubiquitin-conjugating enzyme family. UBE2D2 takes part in the ubiquitination of the tumor-suppressor protein p53, which is induced by an E3 ubiquitin-protein ligase. UBE2D2 catalyzes ubiquitination of IkB-alpha in a SCFB-TRCP and phosphorylation dependent method.

UBE2D1 is a member of the ubiquitin-conjugating enzyme family. Ubiquitination involves at least 3 classes of enzymes: ubiquitin-activating enzymes (E1s), ubiquitin-conjugating enzymes (E2s) and ubiquitin-protein ligases (E3s). UBE2D1 is strongly related to a stimulator of iron transport (SFT), and is up-regulated in hereditary hemochromatosis. In addition, UBE2D1 functions in the ubiquitination of the tumor-suppressor protein p53 and the hypoxia-inducible transcription factor HIF1alpha by interacting with the E1 ubiquitin-activating enzyme and the E3 ubiquitin-protein ligases.

UbcH10 is an essential mediator of mitotic destruction events and cell cycle progression. It catalyzes the destruction of cyclins A and B in conjunction with the anaphase-promoting complex, and therefore, plays an important role in the control of the cell exit from mitosis This activity is essential at then end of mitosis for the inactivation of their partner kinase Cdc2 and exit from mitosis into G1 of the next cell cycle. In addition, UbcH10 bears homology to yeast PAS2, a gene that is essential for biogenesis of peroxisomes. UbcH10 is useful for in vitro ubiquitinylation reactions.

This E2 enzyme encodes for the human homolog of the yeast DNA repair gene RAD6, which is induced by DNA damaging agents. UBE2B can conjugate ubiquitin to histone H2A in an E3- independent manner in vitro, and is essential for the multi-ubiquitination and degradation of N-end rule substrates. Additionally, UBE2B may have a role in sepsis-induced muscle protein proteolysis and cancer-induced cachexia.

The alteration of proteins with ubiquitin is a vital cellular mechanism for targeting atypical or short-lived proteins for degradation. Ubiquitination involves noT less than three classes of enzymes: ubiquitin-activating enzymes, or E1s, ubiquitin-conjugating enzymes, or E2s, and ubiquitin-protein ligases, or E3s. UBE2A is part of the E2 ubiquitin-conjugating enzyme family. UBE2A is necessary for post-replicative DNA damage repair. UBE2A catalyzes the covalent attachment of ubiquitin to other proteins. UBE2A is necessary for postreplication repair of UV-damaged DNA.

Ubiquitin-like modifier activating enzyme 5 (UBA5) is a member of the ubiquitin-activating E1 family and UBA5 subfamily. Ubiquitin and ubiquitin-like proteins are recognized as covalently conjugated to various cellular substrates by a three-step enzymatic pathway. The ubiquitin-activating enzyme (E1) has a vital role in the first step of ubiquitination pathway to activate ubiquitin or ubiquitin-like proteins. UBA5 activates an ubiquitin-like protein, ubiquitin-fold modifier 1 (Ufm1), by forming a high-energy thioester bond. UBA5 is located primarily in cytoplasm, while it generally localizes to the nucleus in presence of SUMO2.

NEDD8-activating enzyme E1 catalytic subunit (UBA3) is the catalytic subunit of the dimeric UBA3-NAE1 E1 enzyme, which belongs to the E1 ubiquitin-activating enzyme family. E1 activates NEDD8 by initially adenylating its C-terminal glycine residue with ATP, afterwards linking this residue to the side chain of the catalytic cysteine, generating a NEDD8-UBA3 thioester and free AMP. E1 at last transfers NEDD8 to the catalytic cysteine of UBE2M. The UBA3 enzyme connects with AppBp1, an amyloid beta precursor protein binding protein, to form a heterodimer, and at that point the enzyme complex activates NEDD8, a ubiquitin-like protein, which controls cell division, signaling and embryogenesis.

SUMO-activating enzyme subunit 2 (UBA2) belongs to a family of small and related proteins which can be enzymatically attached to a target protein by a post-translational modification process termed sumoylation. UBA2 is conjugated to various molecules in the presence of the SAE1/UBA2 SUMO-activating(E1) enzyme and the UBE2I/Ubc9 SUMO-conjugating(E2) enzyme. UBA2 represents a vital mechanism to protect neurons during episodes of cerebral ischemia.

NEDD8 is part of the ubiquitin family. Human NEDD8 shares 60% amino acid sequence homology to ubiquitin. The NEDD8 system is essential for the regulation of protein degradation pathways involved in cell cycle progression, morphogenesis and tumorigenesis. NEDD8 is involved in cell cycle control and embryogenesis. Covalent attachment to its substrates requires prior activation by the E-1 complex UbE1c- appbp1 and linkage to the E-2 enzyme UbE2m. Attachment of NEDD8 to cullins activates their associated E-3 ubiquitin ligase activity, and thus promotes polyubiquitination and proteasomal degradation of cyclins and other regulatory proteins.

SAE1 and SAE2 form heterodimers which take part in the posttranslational modification of proteins (sumoylation). This process regulates protein structure as well as intracellular localization of the target. SAE1/SAE2 may indicate on dermatomyositis (DM) as autoantibodies against those 2 proteins have been found in patients.

SAE1 is part of the ubiquitin-activating E1 family of proteins and participates in the significant first step of the UBL1 conjugation pathway. Proteins conjugated to Ub are marked for progressive degradation by the 26S Proteasome. SAE1 acts as a UBLI E1 ligase mediating the ATP-dependent activation of UBL1. SAE1 binds with UBLE1A and UBLE1B to form a heterodimer which can bind UBL1. SAE1 is a dimeric enzyme that takes part as a E1 ligase for SUMO1, SUMO2, SUMO3, and probably SUMO4. SAE1 regulates ATP-dependent activation of SUMO proteins and formation of a thioester with a conserved cysteine residue on SAE2.