What are the large channel proteins in the outer membrane of gram-negative bacteria called?

The large channel proteins found in the outer membrane of gram-negative bacteria are known as porins. These proteins facilitate the transport of small molecules, ions, and nutrients into the bacterial cell while acting as a selective barrier. Porins are typically beta-barrel structures that form hydrophilic channels, allowing the passive movement of substances across the outer membrane. This characteristic is crucial for the survival of gram-negative bacteria, as their unique cell wall structure includes an outer membrane that separates the cytoplasm from the environment.

Pores are a more general term that can refer to openings in membranes but do not specifically denote the structural and functional properties unique to porins. Glycoproteins, while they can play various roles in cellular processes, do not specifically describe the channel proteins found in the outer membrane of gram-negative bacteria. Transporters refer to proteins that actively move substances across membranes, often against their concentration gradient, which contrasts with the passive function of porins. Hence, the specific identification of these channel proteins as porins highlights their importance in the physiology of gram-negative bacteria.