Cellular Roles
To transport medium-sized or charged molecules across, the molecules move through a porin, a water-filled channel or pore.
Porins typically control the diffusion of small metabolites like sugars, ions, and amino acids.
In gram-negative bacteria, the inner membrane is the major permeability barrier, whereas the outer membrane contains porins, which render 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. However, they are often considered distinct from other porins (they are not classified as porins in MeSH.)
Porins are chemically selective – transport only one group of molecules, or may be specific for one molecule. Beta-lactam and fluoroquinolone antibiotics must pass through porins to reach their targets in gram negative bacteria. Bacteria can develop resistance to these antibiotics by mutating the gene that encodes the porin – the antibiotics are then excluded from passing through the outer membrane.
Read more about this topic: Porin (protein)
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