RING finger (Really Interesting New Gene) domain and U-box domain superfamily; The RING finger is a specialized type of Zn-finger of 40 to 60 residues that binds two atoms of zinc. It is defined by the "cross-brace" motif that chelates zinc atoms by eight amino acid residues, typically Cys or His, arranged in a characteristic spacing. Canonical RING motifs have been categorized into two major subclasses, RING-HC (C3HC4-type) and RING-H2 (C3H2C3-type), according to their Cys/His content. There are also many variants of RING fingers: some have different Cys/His patterns while some lack a single Cys or His residue at typical Zn ligand positions (the fourth or eighth zinc ligand is prevalently exchanged for an Asp, which can indeed chelate Zn in a RING finger as well). C4C4-, C3HC3D-, C2H2C4-, and C3HC5-type RING fingers are closely related to RING-HC fingers. In contrast, C4HC3- (RING-CH alias RINGv), C3H3C2-, C3H2C2D-, C3DHC3-, and C4HC2H-type RING fingers are more closely related to RING-H2 fingers. However, not all RING finger-containing proteins display regular RING finger features, and the RING finger family has turned out to be multifarious. The degenerate RING fingers of the Siz/PIAS RING (SP-RING) family proteins and sporulation protein RMD5, are characterized by lacking the second, fifth, and sixth Zn2+ ion-coordinating residues. They bind only one Zn2+ ion. On the other hand, the RING fingers of the human APC11 and RBX1 proteins can bind a third Zn atom since they harbor four additional Zn ligands. U-box is a modified form of the RING finger domain that lacks metal chelating Cys and His residues. It resembles the cross-brace RING structure consisting of three beta-sheets and a single alpha-helix, which would be stabilized by salt bridges instead of chelated metal ions. U-box proteins are widely distributed among eukaryotic organisms and show a higher prevalence in plants than in other organisms. RING finger/U-box-containing proteins are a group of diverse proteins with a variety of cellular functions, including oncogenesis, development, viral replication, signal transduction, the cell cycle and apoptosis. Many of them are ubiquitin-protein ligases (E3s) that serve as scaffolds for binding to ubiquitin-conjugating enzymes (E2s, also referred to as ubiquitin carrier proteins or UBCs) in close proximity to substrate proteins, which enable efficient transfer of ubiquitin from E2 to the substrates.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 84039696    1 MKVKIKCWNGVATWLW-VANDENCGICRMAFNGCCPDCKVPGDDCPLVWGQCSHCFHMHCILKWLNAQQVQQHCPMCRQE 79
Cdd:pfam12861  1 MKVKIKEWNAVATWLWdVPSDDVCGICRVSFDGTCPDCKFPGDDCPLVWGKCSHNFHMHCILKWLHTETSKGLCPMCRQT 80

                 ....*
gi 84039696   80 WKFKE 84
Cdd:pfam12861 81 FKFAE 85

Anaphase-promoting complex subunit 11 RING-H2 finger; Apc11 is one of the subunits of the anaphase-promoting complex or cyclosome. The APC subunits are cullin family proteins with ubiquitin ligase activity. Polyubiquitination marks proteins for degradation by the 26S proteasome and is carried out by a cascade of enzymes that includes ubiquitin-activating enzymes (E1s), ubiquitin-conjugating enzymes (E2s), and ubiquitin ligases (E3s). Apc11 acts as an E3 enzyme and is responsible for recruiting E2s to the APC and for mediating the subsequent transfer of ubiquitin to APC substrates in vivo. In Saccharomyces cerevisiae this RING-H2 finger protein defines the minimal ubiquitin ligase activity of the APC, and the integrity of the RING-H2 finger is essential for budding yeast cell viability.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 84039696    1 MKVKIKCWNGVATWLW-VANDENCGICRMAFNGCCPDCKVPGDDCPLVWGQCSHCFHMHCILKWLNAQQVQQHCPMCRQE 79
Cdd:pfam12861  1 MKVKIKEWNAVATWLWdVPSDDVCGICRVSFDGTCPDCKFPGDDCPLVWGKCSHNFHMHCILKWLHTETSKGLCPMCRQT 80

                 ....*
gi 84039696   80 WKFKE 84
Cdd:pfam12861 81 FKFAE 85

Component of SCF ubiquitin ligase and anaphase-promoting complex [Posttranslational modification, protein turnover, chaperones / Cell division and chromosome partitioning];

                       10        20        30        40        50        60        70        80
               ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 84039696  1 MKVKIKCWNGVATWLWVANDENCGICRMAFNGCCPDCK---VPGDDCPLVWGQCSHCFHMHCILKWLNAQQVqqhCPMCR 77
Cdd:COG5194  1 MKVKIKKWHAVALWSWDIPIDVCAICRNHIMGTCPECQfgmTPGDECPVVWGVCNHAFHDHCIYRWLDTKGV---CPLDR 77

               ....*
gi 84039696 78 QEWKF 82
Cdd:COG5194 78 QTWVL 82

Anaphase-promoting complex subunit 11 RING-H2 finger; Apc11 is one of the subunits of the anaphase-promoting complex or cyclosome. The APC subunits are cullin family proteins with ubiquitin ligase activity. Polyubiquitination marks proteins for degradation by the 26S proteasome and is carried out by a cascade of enzymes that includes ubiquitin-activating enzymes (E1s), ubiquitin-conjugating enzymes (E2s), and ubiquitin ligases (E3s). Apc11 acts as an E3 enzyme and is responsible for recruiting E2s to the APC and for mediating the subsequent transfer of ubiquitin to APC substrates in vivo. In Saccharomyces cerevisiae this RING-H2 finger protein defines the minimal ubiquitin ligase activity of the APC, and the integrity of the RING-H2 finger is essential for budding yeast cell viability.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 84039696    1 MKVKIKCWNGVATWLW-VANDENCGICRMAFNGCCPDCKVPGDDCPLVWGQCSHCFHMHCILKWLNAQQVQQHCPMCRQE 79
Cdd:pfam12861  1 MKVKIKEWNAVATWLWdVPSDDVCGICRVSFDGTCPDCKFPGDDCPLVWGKCSHNFHMHCILKWLHTETSKGLCPMCRQT 80

                 ....*
gi 84039696   80 WKFKE 84
Cdd:pfam12861 81 FKFAE 85

Component of SCF ubiquitin ligase and anaphase-promoting complex [Posttranslational modification, protein turnover, chaperones / Cell division and chromosome partitioning];

                       10        20        30        40        50        60        70        80
               ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 84039696  1 MKVKIKCWNGVATWLWVANDENCGICRMAFNGCCPDCK---VPGDDCPLVWGQCSHCFHMHCILKWLNAQQVqqhCPMCR 77
Cdd:COG5194  1 MKVKIKKWHAVALWSWDIPIDVCAICRNHIMGTCPECQfgmTPGDECPVVWGVCNHAFHDHCIYRWLDTKGV---CPLDR 77

               ....*
gi 84039696 78 QEWKF 82
Cdd:COG5194 78 QTWVL 82

modified RING finger, H2 subclass (C3H2C2D-type), found in RING-box protein 1 (RBX1) and similar proteins; RBX1, also known as Hrt1, protein ZYP, RING finger protein 75 (RNF75), or regulator of cullins 1 (ROC1), is an E3 ubiquitin-protein ligase necessary for ubiquitin ligation activity of multimeric cullin (Cul)-RING E3 ligases (CRLs). RBX1-containing CRLs are involved in the NEDD8 pathway; RBX1 specifically regulates NEDD8ylation of Cul1-4. It can also bind and activate HIV-1 Vif-Cullin5 E3 ligase complex in vitro. Moreover, RBX1 is an essential element of Skp1/Cullin/F-box (SCF) E3-ubiquitin ligase complexes that target diverse proteins for proteasome-mediated degradation. It is a direct functional target of miR-194 and plays an important role in proliferation and migration of gastric cancer (GC) cells. RBX1 is also an essential component of KEAP1/CUL3/RBX1 E3-ubiquitin ligase complex that functions as a regulator of NFE2-related factor 2 (NRF2) and plays a key role in NRF2 pathway deregulation in multiple tumor types, including ovarian carcinomas (OVCA) and papillary thyroid carcinoma (PTC). Furthermore, RBX1 associates with DDB1, Cul4A, and Fbxw5 to form the Fbxw5-DDB1-Cul4A-Rbx1 complex that may function as a dual SUMO/ubiquitin ligase suppressing c-Myb activity through sumoylation or ubiquitination. RBX1 contains a C-terminal modified RING-H2 finger that is of C3H2C2D-type, rather than the canonical C3H2C3-type. The modified RING-H2 finger is essential for its ligase activity.

                       10        20        30        40        50        60
               ....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 84039696 21 ENCGICRMAFNGCCPDCK-----VPGDDCPLVWGQCSHCFHMHCILKWLNAQQVqqhCPMCRQEW 80
Cdd:cd16485  1 DNCAICRNHIMDLCIECQanqasATSEECTVAWGVCNHAFHFHCISRWLKTRQV---CPLDNREW 62

RING finger (Really Interesting New Gene) domain and U-box domain superfamily; The RING finger is a specialized type of Zn-finger of 40 to 60 residues that binds two atoms of zinc. It is defined by the "cross-brace" motif that chelates zinc atoms by eight amino acid residues, typically Cys or His, arranged in a characteristic spacing. Canonical RING motifs have been categorized into two major subclasses, RING-HC (C3HC4-type) and RING-H2 (C3H2C3-type), according to their Cys/His content. There are also many variants of RING fingers: some have different Cys/His patterns while some lack a single Cys or His residue at typical Zn ligand positions (the fourth or eighth zinc ligand is prevalently exchanged for an Asp, which can indeed chelate Zn in a RING finger as well). C4C4-, C3HC3D-, C2H2C4-, and C3HC5-type RING fingers are closely related to RING-HC fingers. In contrast, C4HC3- (RING-CH alias RINGv), C3H3C2-, C3H2C2D-, C3DHC3-, and C4HC2H-type RING fingers are more closely related to RING-H2 fingers. However, not all RING finger-containing proteins display regular RING finger features, and the RING finger family has turned out to be multifarious. The degenerate RING fingers of the Siz/PIAS RING (SP-RING) family proteins and sporulation protein RMD5, are characterized by lacking the second, fifth, and sixth Zn2+ ion-coordinating residues. They bind only one Zn2+ ion. On the other hand, the RING fingers of the human APC11 and RBX1 proteins can bind a third Zn atom since they harbor four additional Zn ligands. U-box is a modified form of the RING finger domain that lacks metal chelating Cys and His residues. It resembles the cross-brace RING structure consisting of three beta-sheets and a single alpha-helix, which would be stabilized by salt bridges instead of chelated metal ions. U-box proteins are widely distributed among eukaryotic organisms and show a higher prevalence in plants than in other organisms. RING finger/U-box-containing proteins are a group of diverse proteins with a variety of cellular functions, including oncogenesis, development, viral replication, signal transduction, the cell cycle and apoptosis. Many of them are ubiquitin-protein ligases (E3s) that serve as scaffolds for binding to ubiquitin-conjugating enzymes (E2s, also referred to as ubiquitin carrier proteins or UBCs) in close proximity to substrate proteins, which enable efficient transfer of ubiquitin from E2 to the substrates.

                       10        20        30        40        50
               ....*....|....*....|....*....|....*....|....*....|....
gi 84039696 23 CGICRMAFNGCCPdckvpgddcpLVWGQCSHCFHMHCILKWLNAQqvQQHCPMC 76
Cdd:cd00162  1 CPICREEMNDRRP----------VVLLSCGHTFSRSAIARWLEGS--KQKCPFC 42

H2 subclass of RING (RING-H2) fingers and its variants; The RING finger is a specialized type of Zn-finger of 40 to 60 residues that binds two atoms of zinc. It is defined by the "cross-brace" motif that chelates zinc atoms by eight amino acid residues, typically Cys or His, arranged in a characteristic spacing. Canonical RING motifs have been categorized into two major subclasses, RING-HC (C3HC4-type) and RING-H2 (C3H2C3-type), according to their Cys/His content. There are also many variants of RING fingers: some have different Cys/His patterns while some lack a single Cys or His residue at typical Zn ligand positions (the fourth or eighth zinc ligand is prevalently exchanged for an Asp, which can indeed chelate Zn in a RING finger as well). This family corresponds to the H2 subclass of RING (RING-H2) finger proteins that are characterized by containing C3H2C3-type canonical RING-H2 fingers or noncanonical RING-H2 finger variants, including C4HC3- (RING-CH alias RINGv), C3H3C2-, C3H2C2D-, C3DHC3-, and C4HC2H-type modified RING-H2 fingers. The canonical RING-H2 finger has been defined as C-X2-C-X(9-39)-C-X(1-3)-H-X(2-3)-H-X2-C-X(4-48)-C-X2-C, X is any amino acid and the number of X residues varies in different fingers. It binds two Zn ions in a unique "cross-brace" arrangement, which distinguishes it from tandem zinc fingers and other similar motifs. RING-H2 finger can be found in a group of diverse proteins with a variety of cellular functions, including oncogenesis, development, viral replication, signal transduction, the cell cycle and apoptosis. Many of them are ubiquitin-protein ligases (E3s) that serves as a scaffold for binding to ubiquitin-conjugating enzymes (E2s, also referred to as ubiquitin carrier proteins or UBCs) in close proximity to substrate proteins, which enables efficient transfer of ubiquitin from E2 to the substrates.

                       10        20        30        40        50
               ....*....|....*....|....*....|....*....|....*....|....*
gi 84039696 23 CGICRMAFngccpdckvpGDDCPLVWGQCSHCFHMHCILKWLnaQQVQQHCPMCR 77
Cdd:cd16448  1 CVICLEEF----------EEGDVVRLLPCGHVFHLACILRWL--ESGNNTCPLCR 43

RING finger, H2 subclass, found in RING-box protein 2 (RBX2) and similar proteins; RBX2, also known as CKII beta-binding protein 1 (CKBBP1), RING finger protein 7 (RNF7), regulator of cullins 2 (ROC2), or sensitive to apoptosis gene protein (SAG), is an E3 ubiquitin-protein ligase that protects cells from apoptosis, confers radioresistance, and plays an essential and non-redundant role in embryogenesis and vasculogenesis. It promotes ubiquitination and degradation of a number of protein substrates, including c-JUN, DEPTOR, HIF-1alpha, IkappaBalpha, NF1, NOXA, p27, and procaspase-3, thus regulating various signaling pathways and biological processes. RBX2 is necessary for ubiquitin ligation activity of the multimeric cullin (Cul)-RING E3 ligases (CRLs). RBX2-containing CRLs are involved in the NEDD8 pathway and RBX2 specifically regulates NEDD8ylation of Cul5. It can bind and activate the HIV-1 Vif-Cullin5 E3 ligase complex in vitro. It is also a substrate of NEDD4-1 E3 ubiquitin ligase and mediates NEDD4-1 induced chemosensitization. The inactivation of RBX2 E3 ubiquitin ligase activity triggers senescence and inhibits Kras-induced immortalization. Endothelial deletion of RBX2 causes embryonic lethality and blocks tumor angiogenesis, and may have potential use in anti-angiogenesis therapy of human cancers. Moreover, as a component of the Cullin 5-RING E3 ubiquitin ligase (CRL5) complex, RBX2 regulates neuronal migration through different CRL5 adaptors, such as SOCS7. RBX2 also functions as a redox inducible antioxidant protein that scavenges oxygen radicals by forming inter- and intra-molecular disulfide bonds when acting alone. It contains a C-terminal C3H2C3-type RING-H2 finger that is essential for its ligase activity.

                       10        20        30        40        50        60
               ....*....|....*....|....*....|....*....|....*....|....*....|
gi 84039696 23 CGICRMAFNGCCPDCK--VPGDDCPLVWGQCSHCFHMHCILKWLNAqqvQQHCPMCRQEW 80
Cdd:cd16466  4 CAICRVQVMDACLRCQaeNKQEDCVVVWGECNHSFHNCCMSLWVKQ---NNRCPLCQQDW 60

RING finger, H2 subclass, found in synoviolin and similar proteins; Synoviolin, also known as synovial apoptosis inhibitor 1 (Syvn1), Hrd1, or Der3, is an endoplasmic reticulum (ER)-anchoring E3 ubiquitin ligase that functions as a suppressor of ER stress-induced apoptosis and plays a role in homeostasis maintenance. It also targets tumor suppressor gene p53 for proteasomal degradation, suggesting crosstalk between ER associated degradation (ERAD) and p53 mediated apoptotic pathway under ER stress. Moreover, synoviolin controls body weight and mitochondrial biogenesis through negative regulation of the thermogenic coactivator peroxisome proliferator-activated receptor coactivator (PGC)-1beta. It upregulates amyloid beta production by targeting a negative regulator of gamma-secretase, Retention in endoplasmic reticulum 1 (Rer1), for degradation. It is also involved in the degradation of endogenous immature nicastrin, and affects amyloid beta-protein generation. Moreover, synoviolin is highly expressed in rheumatoid synovial cells and may be involved in the pathogenesis of rheumatoid arthritis (RA). It functions as an anti-apoptotic factor that is responsible for the outgrowth of synovial cells during the development of RA. It promotes inositol-requiring enzyme 1 (IRE1) ubiquitination and degradation in synovial fibroblasts with collagen-induced arthritis. Furthermore, the upregulation of synoviolin may represent a protective response against neurodegeneration in Parkinson's disease (PD). In addition, synoviolin is involved in liver fibrogenesis. Synoviolin contains a C3H2C2-type RING-H2 finger.

                       10        20
               ....*....|....*....|....*..
gi 84039696 51 CSHCFHMHCILKWLnaqQVQQHCPMCR 77
Cdd:cd16479 20 CGHIFHLSCLRSWL---QRQQTCPTCR 43

RING finger, H2 subclass, found in Arabidopsis thaliana RING-H2 finger A1a (RHA1A), A1b (RHA1B) and similar proteins; This subfamily includes Arabidopsis thaliana RHA1A, RHA1B and XERICO. RHA1A is a probable E3 ubiquitin-protein ligase that may possess E3 ubiquitin ligase activity in vitro. RHA1B possesses E3 ubiquitin-protein ligase activity when associated with the E2 enzyme UBC8 in vitro. XERICO functions on abscisic acid homeostasis at post-translational level, probably through ubiquitin/proteasome-dependent substrate-specific degradation. Members of this subfamily contain a C3H2C3-type RING-H2 finger.

                       10        20        30        40        50        60
               ....*....|....*....|....*....|....*....|....*....|....*....|.
gi 84039696 20 DENCGICRMAFNGccpdckvpgDDCPLVWGQCSHCFHMHCILKWLNAQQVQqhCPMCRQEW 80
Cdd:cd23121  1 DDCCAICLSDFNS---------DEKLRQLPKCGHIFHHHCLDRWIRYNKIT--CPLCRADL 50