Ductin--a proton pump component, a gap junction channel and a neurotransmitter release channel.
Ductin is the highest conserved membrane protein yet found in eukaryotes. It is multifunctional, being the subunit c or proteolipid component of the vacuolar H(+)-ATPase and at the same time the protein component of a form of gap junction in metazoan animals. Analysis of its structure shows it to be a tandem repeat of two 8-kDa domains derived from the subunit c of the F0 proton pore from the F1F0 ATPase. Each domain contains two transmembrane alpha-helices, which together may form a four-helix bundle. In both the V-ATPase and gap junction channel, ductin is probably arranged as a hexamer of subunits forming a central channel of gap junction-like proportions. The two functions appear to be seggregated by ductin having two orientations in the bilayer. Ductin is also the major component of the mediatophore, a protein complex which may aid in the release of neurotransmitters across the pre-synaptic membrane. It is also a target for a class of poorly understood viral polypeptides. These polypeptides are small and highly hydrophobic and some have oncogenic activity. Ductin thus appears to be at the crossroads of a number of biological processes.
Finbow
M E
ME
CRC Beatson Laboratories, Beatson Institute for Cancer Research, Bearsden, Glasgow, Scotland.
Harrison
M
M
Jones
P
P
D000595:Amino Acid Sequence; D000818:Animals; D017629:Gap Junctions / Q000378:metabolism*; D006801:Humans; D007473:Ion Channels / Q000378:metabolism*; D008969:Molecular Sequence Data; D011510:Proteolipids / Q000502:physiology*; D017494:Proton Pumps; D006180:Proton-Translocating ATPases / Q000502:physiology*; D025262:Vacuolar Proton-Translocating ATPases
D007473:Ion Channels; D011510:Proteolipids; D017494:Proton Pumps; C082471:ductin; D025262:Vacuolar Proton-Translocating ATPases; D006180:Proton-Translocating ATPases