Eiwitsecretiesystemen bij Gram-negatieve bacteriën

Gram-negative bacteria have one-step and two-step protein secretion systems for translocation into the outer lipopolysaccharide membrane or extracellular release.

The one-step secretion systems, types I, III, IV, and VI, bypass the periplasm and form connected channels across both membranes.

Type I systems transport substrates such as toxins directly out of the cell, while type III systems, often termed injectisomes, deliver effector proteins into host cells during infection.

Type IV systems facilitate DNA transfer in horizontal gene transfer, while type VI systems use a phage-like contraction mechanism to inject toxins into competing bacteria or host cells.

The two-step secretion systems, types II and V, depend on the Sec or Tat system to move proteins across the inner membrane.

Type II secretion systems use a pseudopilus to push proteins, such as toxins and enzymes, from the periplasm across the outer membrane.

Type V systems release proteins extracellularly or retain them in the outer membrane as adhesins.