Porins are transmembrane proteins that are large enough to facilitate passive diffusion. They are prevalent in the outer membrane of the mitochondria and Gram-negative bacteria.

Porins are almost entirely composed of beta sheets and control the diffusion of small metabolites like sugars, ions, and amino acids. Although the inner membrane is a major permeability barrier, the outer membrane contains porin which renders it largely permeable to molecules less than about 1500 daltons.

The term "nucleoporin" refers to porins facilitating transport through nuclear pores in the nuclear envelope.

See also

• Aquaporin

References

• The human beta barrel porin protein
• history at leeds.ac.uk

Proteins

Porin (Protein)