Abstract
Type-3 secretion system injectisomes are multiprotein complexes that translocate bacterial effector proteins from the cytoplasm of gram-negative bacteria directly into the cytosol of eukaryotic host cells. These systems are present in more than 30 bacterial species, including numerous human, animal, and plant pathogens. We review recent discoveries of structural and molecular mechanisms of effector protein translocation through the injectisomes and recent advances in the understanding of mechanisms of activation of effector protein secretion.