RING finger, HC subclass, found in E3 ubiquitin-protein ligase Hakai, zinc finger protein 645 (ZNF645), and similar proteins; Hakai, also known as Casitas B-lineage lymphoma-transforming sequence-like protein 1, RING finger protein 188 (RNF188), or c-Cbl-like protein 1 (CBLL1), is an E3 ubiquitin ligase that disrupts cell-cell contacts in epithelial cells and is upregulated in human colon and gastric adenocarcinomas. It was identified to mediate the posttranslational downregulation of E-cadherin (CDH1), a major component of adherens junctions in epithelial cells and a potent tumor suppressor. It also promotes ubiquitination of several other tyrosine-phosphorylated Src substrates, including cortactin (CTTN) and DOK1. Hakai acts as a homodimer arranged in an anti-parallel configuration with a novel HYB (Hakai pTyr-binding) domain that forms a phosphotyrosine-binding pocket. Each monomer contains a C3HC4-type RING-HC finger and a short pTyr-B domain that incorporates a novel, atypical C2H2-type Zn-finger coordination motif. Both domains are important for dimerization. ZNF645 is a novel testis-specific E3 ubiquitin-protein ligase that plays a role in sperm production and quality control. It has a structure similar to that of the c-Cbl-like protein Hakai. In contrast to Hakai, its HYB domain demonstrates different target specificities. It interacts with v-Src-phosphorylated E-cadherin, but not to cortactin.

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                ....*....|....*....|....*....|....*....|....*....|..
gi 19921556 169 HCCDQCDKPILVYGRMIPCKHVFCLKCARAEpIKSCPRCTDKVLRVEQSGLG 220
Cdd:cd16508   1 HFCDKCDLPIKIYGRMIPCKHVFCLDCARLH-DKICPRCDDPVQRIEQCTRG 51

RING finger, HC subclass, found in E3 ubiquitin-protein ligase Hakai, zinc finger protein 645 (ZNF645), and similar proteins; Hakai, also known as Casitas B-lineage lymphoma-transforming sequence-like protein 1, RING finger protein 188 (RNF188), or c-Cbl-like protein 1 (CBLL1), is an E3 ubiquitin ligase that disrupts cell-cell contacts in epithelial cells and is upregulated in human colon and gastric adenocarcinomas. It was identified to mediate the posttranslational downregulation of E-cadherin (CDH1), a major component of adherens junctions in epithelial cells and a potent tumor suppressor. It also promotes ubiquitination of several other tyrosine-phosphorylated Src substrates, including cortactin (CTTN) and DOK1. Hakai acts as a homodimer arranged in an anti-parallel configuration with a novel HYB (Hakai pTyr-binding) domain that forms a phosphotyrosine-binding pocket. Each monomer contains a C3HC4-type RING-HC finger and a short pTyr-B domain that incorporates a novel, atypical C2H2-type Zn-finger coordination motif. Both domains are important for dimerization. ZNF645 is a novel testis-specific E3 ubiquitin-protein ligase that plays a role in sperm production and quality control. It has a structure similar to that of the c-Cbl-like protein Hakai. In contrast to Hakai, its HYB domain demonstrates different target specificities. It interacts with v-Src-phosphorylated E-cadherin, but not to cortactin.

                        10        20        30        40        50
                ....*....|....*....|....*....|....*....|....*....|..
gi 19921556 169 HCCDQCDKPILVYGRMIPCKHVFCLKCARAEpIKSCPRCTDKVLRVEQSGLG 220
Cdd:cd16508   1 HFCDKCDLPIKIYGRMIPCKHVFCLDCARLH-DKICPRCDDPVQRIEQCTRG 51

RING finger, HC subclass, found in E3 ubiquitin-protein ligase Hakai, zinc finger protein 645 (ZNF645), and similar proteins; Hakai, also known as Casitas B-lineage lymphoma-transforming sequence-like protein 1, RING finger protein 188 (RNF188), or c-Cbl-like protein 1 (CBLL1), is an E3 ubiquitin ligase that disrupts cell-cell contacts in epithelial cells and is upregulated in human colon and gastric adenocarcinomas. It was identified to mediate the posttranslational downregulation of E-cadherin (CDH1), a major component of adherens junctions in epithelial cells and a potent tumor suppressor. It also promotes ubiquitination of several other tyrosine-phosphorylated Src substrates, including cortactin (CTTN) and DOK1. Hakai acts as a homodimer arranged in an anti-parallel configuration with a novel HYB (Hakai pTyr-binding) domain that forms a phosphotyrosine-binding pocket. Each monomer contains a C3HC4-type RING-HC finger and a short pTyr-B domain that incorporates a novel, atypical C2H2-type Zn-finger coordination motif. Both domains are important for dimerization. ZNF645 is a novel testis-specific E3 ubiquitin-protein ligase that plays a role in sperm production and quality control. It has a structure similar to that of the c-Cbl-like protein Hakai. In contrast to Hakai, its HYB domain demonstrates different target specificities. It interacts with v-Src-phosphorylated E-cadherin, but not to cortactin.

                        10        20        30        40        50
                ....*....|....*....|....*....|....*....|....*....|..
gi 19921556 169 HCCDQCDKPILVYGRMIPCKHVFCLKCARAEpIKSCPRCTDKVLRVEQSGLG 220
Cdd:cd16508   1 HFCDKCDLPIKIYGRMIPCKHVFCLDCARLH-DKICPRCDDPVQRIEQCTRG 51

HC subclass of RING (RING-HC) finger 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 a different Cys/His pattern. Some lack a single Cys or His residue at typical Zn ligand positions, especially, the fourth or eighth zinc ligand is prevalently exchanged for an Asp, which can chelate Zn in a RING finger as well. This family corresponds to the HC subclass of RING (RING-HC) fingers that are characterized by containing C3HC4-type canonical RING-HC fingers or noncanonical RING-HC finger variants, including C4C4-, C3HC3D-, C2H2C4-, and C3HC5-type modified RING-HC fingers. The canonical RING-HC finger has been defined as C-X2-C-X(9-39)-C-X(1-3)-H-X(2-3)-C-X2-C-X(4-48)-C-X2-C. It binds two Zn ions in a unique "cross-brace" arrangement, which distinguishes it from tandem zinc fingers and other similar motifs. RING-HC fingers 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 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 enables efficient transfer of ubiquitin from E2 to the substrates.

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                ....*....|....*....|....*....|....*....|.
gi 19921556 170 CCDQCDKPILvygrmIPCKHVFCLKCARA---EPIKSCPRC 207
Cdd:cd16449   6 CLERLKDPVL-----LPCGHVFCRECIRRlleSGSIKCPIC 41