Porins B and C are
cell wall
A cell wall is a structural layer that surrounds some Cell type, cell types, found immediately outside the cell membrane. It can be tough, flexible, and sometimes rigid. Primarily, it provides the cell with structural support, shape, protection, ...
channel-forming proteins from ''
Corynebacterium
''Corynebacterium'' () is a genus of Gram-positive bacteria and most are aerobic. They are bacilli (rod-shaped), and in some phases of life they are, more specifically, club-shaped, which inspired the genus name ('' coryneform'' means "club-s ...
''. Porin B from ''Corynebacterium glutamicum'' (Brevibacterium flavum) allows the exchange of material across the mycolic acid layer, which is the protective nonpolar barrier. Porin B has an
alpha helical core
structure
A structure is an arrangement and organization of interrelated elements in a material object or system, or the object or system so organized. Material structures include man-made objects such as buildings and machines and natural objects such as ...
consisting of four
alpha-helices
An alpha helix (or α-helix) is a sequence of amino acids in a protein that are twisted into a coil (a helix).
The alpha helix is the most common structural arrangement in the secondary structure of proteins. It is also the most extreme type of l ...
surrounding a nonpolar interior. There is a
disulfide bridge between
helices
A helix (; ) is a shape like a cylindrical coil spring or the thread of a machine screw. It is a type of smoothness (mathematics), smooth space curve with tangent lines at a constant angle to a fixed axis. Helices are important in biology, as ...
1 and 4 to form a stable covalently bound ring.
The channel of PorB is oligomeric.
References
{{InterPro content, IPR021114
Protein families