| Type: | Conserved_site | Name: | Porin, Gram-negative type, conserved site |
| Description: | Porins are found in the outer membranes of Gram-negative bacteria, mitochondria and chloroplasts, where they form ion-selective channels forsmall hydrophilic molecules (up to ~600 D) [, ]. X-ray structureanalyses of several bacterial porins [, , ] have revealed a large 16-strandedanti-parallel beta-barrel structure enclosing the transmembrane pore, by contrast with all other integral membrane proteins described to date,which are alpha-helical. Three subunits form a trimer; the 3-fold axis is approximately parallel to the barrel axes and is assumed to beperpendicular to the membrane plane.From the range of porins now known, similarities have been observed between porins from different species, and between porins of different specificitywithin the same species. But most porins cannot be related to each other on the basis of sequence alone, and this is reflected in the lengths of theknown porin sequences, which range from 282-483 residues/monomer.This entry represents a conserved region found in porins from Gram-negative bacteria. It is located in the C-terminal part of these proteins and spans two putative transmembrane beta strands. | Short Name: | Porin_Gram-ve_CS |
