Connexin: Difference between revisions
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=Introduction= | =Introduction= | ||
[http://en.wikipedia.org/wiki/Connexin Connexins] are integral transmembrane [http://en.wikipedia.org/wiki/Protein proteins] that form intercellular channels in [http://www.ucmp.berkeley.edu/vertebrates/vertintro.html vertebrates]. Connexin 26 is encoded by the [http://www.uniprot.org/uniprot/P29033 GJB2 gene]. Six connexins form a hexamerical assembly, known as [http://en.wikipedia.org/wiki/Connexon connexon] or hemichannel, which form an intercellular [http://www.ebi.ac.uk/QuickGO/GTerm?id=GO:0005243#term=info gap junction channel]. Gap junctions are specialized membrane regions containing hundreds of intercellular communication channels that allow the passage of molecules such as ions, metabolites, nucleotides and small peptides. Virtually all cells in solid tissues are coupled by gap junctions, thus it is not surprising that mutations in connexin genes have been linked to a variety of [http://omim.org/entry/121011?search=gjb2%20deafness-causing&highlight=deafnesscausing%20deafness%20gjb2%20deaf%20causing Connexin human diseases], including [http://radiopaedia.org/articles/congenital-cardiovascular-anomalies cardiovascular anomalies], [http://www.mayoclinic.org/diseases-conditions/peripheral-neuropathy/basics/definition/con-20019948 peripheral neuropathy], skin disorders, [http://en.wikipedia.org/wiki/Cataract cataracts], and deafness. | [http://en.wikipedia.org/wiki/Connexin Connexins] are integral transmembrane [http://en.wikipedia.org/wiki/Protein proteins] that form intercellular channels in [http://www.ucmp.berkeley.edu/vertebrates/vertintro.html vertebrates]. Connexin 26 is encoded by the [http://www.uniprot.org/uniprot/P29033 GJB2 gene]. Six connexins form a hexamerical assembly, known as [http://en.wikipedia.org/wiki/Connexon connexon] or hemichannel, which form an intercellular [http://www.ebi.ac.uk/QuickGO/GTerm?id=GO:0005243#term=info gap junction channel]. Gap junctions are specialized membrane regions containing hundreds of intercellular communication channels that allow the passage of molecules such as ions, metabolites, nucleotides and small peptides. Virtually all cells in solid tissues are coupled by gap junctions, thus it is not surprising that mutations in connexin genes have been linked to a variety of [http://omim.org/entry/121011?search=gjb2%20deafness-causing&highlight=deafnesscausing%20deafness%20gjb2%20deaf%20causing Connexin human diseases], including [http://radiopaedia.org/articles/congenital-cardiovascular-anomalies cardiovascular anomalies], [http://www.mayoclinic.org/diseases-conditions/peripheral-neuropathy/basics/definition/con-20019948 peripheral neuropathy], skin disorders, [http://en.wikipedia.org/wiki/Cataract cataracts], and deafness. | ||
Of notice, about half of all cases of human pre-lingual recessive deafness in countries surrounding the Mediterranean have been linked to mutations in the [http://www.uniprot.org/uniprot/P29033 GJB2 gene] <ref name='important'>pmid 24624091</ref>,<ref name='Structure'>pmid 19622859</ref> | Of notice, about half of all cases of human pre-lingual recessive deafness in countries surrounding the Mediterranean have been linked to mutations in the [http://www.uniprot.org/uniprot/P29033 GJB2 gene] <ref name='important'>pmid 24624091</ref>,<ref name='Structure'>pmid 19622859</ref> | ||
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==Connexin structure== | ==Connexin structure== | ||
<scene name='70/701426/Connexin_structure2/1'>connexins</scene> are integral transmembranal proteins which consist of α-helical domains in the <scene name='70/701426/Tm1-tm4/1'>transmembranal segments</scene> (TM1-TM4) , <scene name='70/701426/E1_and_e2/1'>two extracellular loops</scene> (E1 and E2), a cytoplasmic loop, an N-terminal helix (NTH), and a C-terminal segment. Each connexin consists of 227 amino acids, and <scene name='70/701426/Conxoxn_structure/1'>Six units of connexin</scene> form a hexamerical assembly , known as <scene name='70/701426/Connexin_26_basic_structure/3'>a connexon</scene>, or a <scene name='70/701426/Connexin_26_basic_structure/5'>hemmichannel</scene>, which delineates <scene name='70/701426/Pore/1'>an aqueous pore</scene> with a minimum diameter of ∼1.2 nm. | <scene name='70/701426/Connexin_structure2/1'>connexins</scene> are integral transmembranal proteins which consist of α-helical domains in the <scene name='70/701426/Tm1-tm4/1'>transmembranal segments</scene> (TM1-TM4) , <scene name='70/701426/E1_and_e2/1'>two extracellular loops</scene> (E1 and E2), a cytoplasmic loop, an N-terminal helix (NTH), and a C-terminal segment. Each connexin consists of 227 amino acids, and <scene name='70/701426/Conxoxn_structure/1'>Six units of connexin</scene> form a hexamerical assembly , known as <scene name='70/701426/Connexin_26_basic_structure/3'>a connexon</scene>, or a <scene name='70/701426/Connexin_26_basic_structure/5'>hemmichannel</scene>, which delineates <scene name='70/701426/Pore/1'>an aqueous pore</scene> with a minimum diameter of ∼1.2 nm. | ||
When two hemichannels from adjacent cells dock and join, leaving a gap of ∼2–3 nm, they may form a gap junction which spans the two plasma membranes and allows the exchange of cytoplasmic molecules with size up to ∼1 kDa. | When two hemichannels from adjacent cells dock and join, leaving a gap of ∼2–3 nm, they may form a gap junction which spans the two plasma membranes and allows the exchange of cytoplasmic molecules with size up to ∼1 kDa. | ||