Connexin: Difference between revisions
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=Structure:= | =Structure:= | ||
==Connexin structure== | ==Connexin structure== | ||
<scene name='70/701426/Connexons_secondary_structure/1'>connexins</scene>are integral α-hellical transmembrane proteins that form intercellular channels in vertebrates . Six connexins form a hexamerical assembly, known as <scene name='70/701426/Connexin_26_basic_structure/2'>Connexon</scene> connexon or hemichannel , which delineates an aqueous pore 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 an intercellular [http://www.uniprot.org/uniprot/P29033 gap junction channel] which spans the two pαlasma membranes and allows the exchange of cytoplasmic molecules with size up to ∼1 kDa. | |||
The height of the modelled structure of the gap junction channel without disordered cytoplasmic loop and C-terminal segment is approximately 155Å. The transmembrane region and membrane surfaces were deduced from the distribution of hydrophobic and aromatic amino acid residues along the noncrystallographic six-fold axis It is a tsuzumi shape, a traditional Japanese drum.<ref name='Structure'/> [[Image:distances a.jpg]] | The height of the modelled structure of the gap junction channel without disordered cytoplasmic loop and C-terminal segment is approximately 155Å. The transmembrane region and membrane surfaces were deduced from the distribution of hydrophobic and aromatic amino acid residues along the noncrystallographic six-fold axis It is a tsuzumi shape, a traditional Japanese drum.<ref name='Structure'/> [[Image:distances a.jpg]] | ||
The protomers in each hexameric connexon are related by a sixfold non-crystallographic symmetry (NCS) axis perpendicular to the membrane plane . The transmembrane region of the channel is 38Å thick.TM2 extends about 19Å from the membrane surface into the cytoplasm. The extracellular region of the connexon extends 23Å from the membrane surface and interdigitates to the opposite connexon by 6Å, resulting in the intercellular ‘gap’ of 40Å. The extracellular lobes are not protruding so much, as indicated by the structural analyses of split gap junction channels with atomic force microscopy and electron microscopy. The relatively flat lobes could be attributed to the conformational change of the extracellular region induced by the docking of two connexons. The diameter of the connexon is biggest at the cytoplasmic side | The protomers in each hexameric connexon are related by a sixfold non-crystallographic symmetry (NCS) axis perpendicular to the membrane plane . The transmembrane region of the channel is 38Å thick.TM2 extends about 19Å from the membrane surface into the cytoplasm. The extracellular region of the connexon extends 23Å from the membrane surface and interdigitates to the opposite connexon by 6Å, resulting in the intercellular ‘gap’ of 40Å. The extracellular lobes are not protruding so much, as indicated by the structural analyses of split gap junction channels with atomic force microscopy and electron microscopy. The relatively flat lobes could be attributed to the conformational change of the extracellular region induced by the docking of two connexons. The diameter of the connexon is biggest at the cytoplasmic side | ||
