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0CXB4_HUMAN*   SwissProt (?) | Description Local Annotation Link Reference
General Information
NameGJB4
DescriptionGap junction beta-4 protein (connexin 30.3) (cx30.3).
SpeciesHomo sapiens (NCBI taxonomy ID: 9606)
GO0005921 gap junction (NAS)
0005243 gap-junction forming channel activity (NAS)
0007154 cell communication (NAS)

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schematic display of those terms with internal associations, click the node and browse the corresponding GO term
Domain Architecture (Details)
InterPro domains assigned to SynO:
The connexins are a family of integral membrane proteins that oligomerise to form intercellular channels that are clustered at gap junctions. These channels are specialised sites of cell-cell contact that allow the passage of ions.ntracellular metabolites and messenger molecules (with molecular weight less than 1-2 kD) from the cytoplasm of one cell to its opposing neighbours. They are found in almost all vertebrate cell types.nd somewhat similar proteins have been cloned from plant species. Invertebrates utilise a different family of molecules.nnexins.hat share a similar predicted secondary structure to the vertebrate connexins.ut have no sequence identity to them . Vertebrate gap junction channels are thought to participate in diverse biological functions. For instance.n the heart they permit the rapid cell-cell transfer of action potentials.nsuring coordinated contraction of the cardiomyocytes. They are also responsible for neurotransmission at specialised electrical synapses. In non-excitable tissues.uch as the liver.hey may allow metabolic cooperation between cells. In the brain.lial cells are extensively-coupled by gap junctions; this allows waves of intracellular Ca2+ to propagate through nervous tissue.nd may contribute to their ability to spatially-buffer local changes in extracellular K+ concentration .The connexin protein family is encoded by at least 13 genes in rodents.ith many homologues cloned from other species. They show overlapping tissue expression patterns.ost tissues expressing more than one connexin type. Their conductances.ermeability to different molecules.hosphorylation and voltage-dependence of their gating.ave been found to vary. Possible communication diversity is increased further by the fact that gap junctions may be formed by the association of different connexin isoforms from apposing cells. However.n vitro studies have shown that not all possible combinations of connexins produce active channels .Hydropathy analysis predicts that all cloned connexins share a common transmembrane (TM) topology. Each connexin is thought to contain 4 TMdomains.ith two extracellular and three cytoplasmic regions. This modelhas been validated for several of the family members by in vitro biochemicalanalysis. Both N- and C-termini are thought to face the cytoplasm.nd thethird TM domain has an amphipathic character.uggesting that it contributesto the lining of the formed-channel. Amino acid sequence identity betweenthe isoforms is ~50-80%.ith the TM domains being well conserved. Bothextracellular loops contain characteristically conserved cysteine residues.hich likely form intramolecular disulphide bonds. By contrast.he singleputative intracellular loop (between TM domains 2 and 3) and the cytoplasmicC-terminus are highly variable among the family members.Six connexins arethought to associate to form a hemi-channel.r connexon. Two connexons theninteract (likely via the extracellular loops of their connexins) to form thecomplete gap junction channel.Two sets of nomenclature have been used to identify the connexins. Thefirst.nd most commonly used.lassifies the connexin molecules accordingto molecular weight.uch as connexin43 (abbreviated to Cx43).ndicatinga connexin of molecular weight close to 43 kD. However.tudies haverevealed cases where clear functional homologues exist across speciesthat have quite different molecular masses; therefore.n alternativenomenclature was proposed based on evolutionary considerations.hichdivides the family into two major subclasses.lpha and beta.ach with anumber of members . Due to their ubiquity and overlapping tissue distributions.t has proved difficult to elucidate the functions of individual connexin isoforms. To circumvent this problem.articular connexin-encoding genes have been subjected to targeted-disruption in mice.nd the phenotype of the resulting animals investigated. Around half the connexin isoforms have been investigated in this manner . Further insight into the functional roles of connexins has come from the discovery that a number of human diseases are caused by mutations in connexin genes. For instance.utations in Cx32 give rise to a form of inherited peripheral neuropathy called X-linked dominant Charcot-Marie-Tooth disease . Similarly.utations in Cx26 are responsible for both autosomal recessive and dominant forms of nonsyndromic deafness. disorder characterised by hearing loss.ith no apparent effects on other organ systems.
  IPR000500:Connexins
InterPro domains unassigned to SynO:
The connexins are a family of integral membrane proteins that oligomerise to form intercellular channels that are clustered at gap junctions. These channels are specialised sites of cell-cell contact that allow the passage of ions.ntracellular metabolites and messenger molecules (with molecular weight less than 1-2 kD) from the cytoplasm of one cell to its opposing neighbours. They are found in almost all vertebrate cell types.nd somewhat similar proteins have been cloned from plant species. Invertebrates utilise a different family of molecules.nnexins.hat share a similar predicted secondary structure to the vertebrate connexins.ut have no sequence identity to them . Vertebrate gap junction channels are thought to participate in diverse biological functions. For instance.n the heart they permit the rapid cell-cell transfer of action potentials.nsuring coordinated contraction of the cardiomyocytes. They are also responsible for neurotransmission at specialised electrical synapses. In non-excitable tissues.uch as the liver.hey may allow metabolic cooperation between cells. In the brain.lial cells are extensively-coupled by gap junctions; this allows waves of intracellular Ca2+ to propagate through nervous tissue.nd may contribute to their ability to spatially-buffer local changes in extracellular K+ concentration .The connexin protein family is encoded by at least 13 genes in rodents.ith many homologues cloned from other species. They show overlapping tissue expression patterns.ost tissues expressing more than one connexin type. Their conductances.ermeability to different molecules.hosphorylation and voltage-dependence of their gating.ave been found to vary. Possible communication diversity is increased further by the fact that gap junctions may be formed by the association of different connexin isoforms from apposing cells. However.n vitro studies have shown that not all possible combinations of connexins produce active channels .Hydropathy analysis predicts that all cloned connexins share a common transmembrane (TM) topology. Each connexin is thought to contain 4 TMdomains.ith two extracellular and three cytoplasmic regions. This modelhas been validated for several of the family members by in vitro biochemicalanalysis. Both N- and C-termini are thought to face the cytoplasm.nd thethird TM domain has an amphipathic character.uggesting that it contributesto the lining of the formed-channel. Amino acid sequence identity betweenthe isoforms is ~50-80%.ith the TM domains being well conserved. Bothextracellular loops contain characteristically conserved cysteine residues.hich likely form intramolecular disulphide bonds. By contrast.he singleputative intracellular loop (between TM domains 2 and 3) and the cytoplasmicC-terminus are highly variable among the family members.Six connexins arethought to associate to form a hemi-channel.r connexon. Two connexons theninteract (likely via the extracellular loops of their connexins) to form thecomplete gap junction channel.Two sets of nomenclature have been used to identify the connexins. Thefirst.nd most commonly used.lassifies the connexin molecules accordingto molecular weight.uch as connexin43 (abbreviated to Cx43).ndicatinga connexin of molecular weight close to 43 kD. However.tudies haverevealed cases where clear functional homologues exist across speciesthat have quite different molecular masses; therefore.n alternativenomenclature was proposed based on evolutionary considerations.hichdivides the family into two major subclasses.lpha and beta.ach with anumber of members . Due to their ubiquity and overlapping tissue distributions.t has proved difficult to elucidate the functions of individual connexin isoforms. To circumvent this problem.articular connexin-encoding genes have been subjected to targeted-disruption in mice.nd the phenotype of the resulting animals investigated. Around half the connexin isoforms have been investigated in this manner . Further insight into the functional roles of connexins has come from the discovery that a number of human diseases are caused by mutations in connexin genes. For instance.utations in Cx32 give rise to a form of inherited peripheral neuropathy called X-linked dominant Charcot-Marie-Tooth disease . Similarly.utations in Cx26 are responsible for both autosomal recessive and dominant forms of nonsyndromic deafness. disorder characterised by hearing loss.ith no apparent effects on other organ systems.This domain is found in the N-terminal region of these proteins.
  IPR013092:Connexin, N-terminal
The connexins are a family of integral membrane proteins that oligomerise to form intercellular channels that are clustered at gap junctions. These channels are specialised sites of cell-cell contact that allow the passage of ions.ntracellular metabolites and messenger molecules (with molecular weight less than 1-2 kD) from the cytoplasm of one cell to its opposing neighbours. They are found in almost all vertebrate cell types.nd somewhat similar proteins have been cloned from plant species. Invertebrates utilise a different family of molecules.nnexins.hat share a similar predicted secondary structure to the vertebrate connexins.ut have no sequence identity to them . Vertebrate gap junction channels are thought to participate in diverse biological functions. For instance.n the heart they permit the rapid cell-cell transfer of action potentials.nsuring coordinated contraction of the cardiomyocytes. They are also responsible for neurotransmission at specialised electrical synapses. In non-excitable tissues.uch as the liver.hey may allow metabolic cooperation between cells. In the brain.lial cells are extensively-coupled by gap junctions; this allows waves of intracellular Ca2+ to propagate through nervous tissue.nd may contribute to their ability to spatially-buffer local changes in extracellular K+ concentration .The connexin protein family is encoded by at least 13 genes in rodents.ith many homologues cloned from other species. They show overlapping tissue expression patterns.ost tissues expressing more than one connexin type. Their conductances.ermeability to different molecules.hosphorylation and voltage-dependence of their gating.ave been found to vary. Possible communication diversity is increased further by the fact that gap junctions may be formed by the association of different connexin isoforms from apposing cells. However.n vitro studies have shown that not all possible combinations of connexins produce active channels .Hydropathy analysis predicts that all cloned connexins share a common transmembrane (TM) topology. Each connexin is thought to contain 4 TMdomains.ith two extracellular and three cytoplasmic regions. This modelhas been validated for several of the family members by in vitro biochemicalanalysis. Both N- and C-termini are thought to face the cytoplasm.nd thethird TM domain has an amphipathic character.uggesting that it contributesto the lining of the formed-channel. Amino acid sequence identity betweenthe isoforms is ~50-80%.ith the TM domains being well conserved. Bothextracellular loops contain characteristically conserved cysteine residues.hich likely form intramolecular disulphide bonds. By contrast.he singleputative intracellular loop (between TM domains 2 and 3) and the cytoplasmicC-terminus are highly variable among the family members.Six connexins arethought to associate to form a hemi-channel.r connexon. Two connexons theninteract (likely via the extracellular loops of their connexins) to form thecomplete gap junction channel.Two sets of nomenclature have been used to identify the connexins. Thefirst.nd most commonly used.lassifies the connexin molecules accordingto molecular weight.uch as connexin43 (abbreviated to Cx43).ndicatinga connexin of molecular weight close to 43 kD. However.tudies haverevealed cases where clear functional homologues exist across speciesthat have quite different molecular masses; therefore.n alternativenomenclature was proposed based on evolutionary considerations.hichdivides the family into two major subclasses.lpha and beta.ach with anumber of members . Due to their ubiquity and overlapping tissue distributions.t has proved difficult to elucidate the functions of individual connexin isoforms. To circumvent this problem.articular connexin-encoding genes have been subjected to targeted-disruption in mice.nd the phenotype of the resulting animals investigated. Around half the connexin isoforms have been investigated in this manner . Further insight into the functional roles of connexins has come from the discovery that a number of human diseases are caused by mutations in connexin genes. For instance.utations in Cx32 give rise to a form of inherited peripheral neuropathy called X-linked dominant Charcot-Marie-Tooth disease . Similarly.utations in Cx26 are responsible for both autosomal recessive and dominant forms of nonsyndromic deafness. disorder characterised by hearing loss.ith no apparent effects on other organ systems.Gap junction beta-5 protein (also called connexin30.3.r Cx30.3) is aconnexin of 266 amino acid residues that shares ~70% amino acid identitywith both Cx31 and Cx31.1. It is most closely related to the latter;together these molecules share a rather restricted expression pattern.eing preferentially expressed in the skin.nd undetectable in most othertissues. Additionally.he genes encoding them have been found to berather closely-linked on mouse chromosome 4 .
  IPR002271:Gap junction beta-5 protein (Cx30.3)
IPR013092:Connexin 
Evalue:-145.259643554687 
Location:2-208IPR002271:CONNEXINB5 
Evalue:0 
Location:254-266IPR002271:CONNEXINB5 
Evalue:0 
Location:244-253IPR002271:CONNEXINB5 
Evalue:0 
Location:234-241
SequencesProtein: CXB4_HUMAN (266 aa)
mRNA: NM_153212
Local Annotation
Synapse Ontology
supporting cells of the nervous system. Glial cells in the brain and spinal cord far outnumber nerve cells. They not only provide physical support, but also respond to injury, regulate the chemical composition surrounding cells, participate in the blood-brain and blood-spinal-cord barriers, form the myelin insulation of nervous pathways, help guide neuronal migration during development, and exchange metabolites with neurons. They may also produce substances that help and hinder regeneration in the spinal cord. The major types of glial cells in the CNS are astrocytes, oligodendrocytes, and microglia.
sdb:0008 Glia  (Evidence:domains)
A neuromuscular junction is the junction of the axon terminal of a motoneuron with the motor end plate, the highly-excitable region of muscle fiber plasma membrane responsible for initiation of action potentials across the muscle's surface.
sdb:0024 neuromuscular junction  (Evidence:domains)
KO assignmentK07623
  Level 3 annotation:
    gap junction protein, beta 4
  Level 2 annotation:
    Membrane and intracellular structural molecules
Loci Structure (Details)Loci index, Chromosomal location, Length, Possible relational loci clusterExon1: 384 residues, 34999364-35000514Exon2: 2 residues, -Jump to CXB4_HUMAN  
Tune and view alternative isoforms
Loci Cluster (Details)Loci: 2506 34999364-35000514 ~-1K 1035(GJB4)(+)Loci: 2507 35019376-35024551 ~-5K 1036(GJB3)(+)Loci: 2508 35031185-35033933 ~-3K 1037(GJA4)(+)Loci: 3791 35421789-35431322 ~-10K 1048(SFPQ)(-)Loci: 2505 34993307-34996699 ~-3K 1034(GJB5)(+)Link out to UCSC