excB

excB is a gene found in some bacterial species, notably Escherichia coli. It encodes a protein that is a component of the type II secretion system (T2SS). The T2SS is a complex machinery used by many Gram-negative bacteria to export a wide range of proteins, including toxins, enzymes, and extracellular matrix-degrading proteins, into the extracellular environment.

The excB protein, along with other components like GspF, forms the inner membrane component of the T2SS secretin channel. This channel is crucial for the assembly and function of the entire secretion apparatus. Specifically, excB is involved in the proper folding and assembly of the secretin pore, which is a large protein complex that spans the outer membrane and acts as a conduit for secreted substrates. Mutations in the excB gene often lead to a complete loss of function of the T2SS, preventing the secretion of its target proteins. Studying excB has provided insights into the intricate mechanisms of protein transport across bacterial membranes and the assembly of complex protein machines.