Carboxy-Terminal Proteolytic Processing of Helicobacter pylori Vacuolating Toxin

The vacA gene of Helicobacter pylori strain 60190 encodes a 1,287-amino-acid protoxin, which undergoes cleavage of a 33-amino-acid amino-terminal signal sequence and carboxy-terminal proteolytic processing to yield a mature secreted toxin. Several features of VacA suggest that it belongs to the autotransporter family of gram-negative bacterial secreted proteins. Based on matrix-assisted laser desorption ionization–time of flight mass spectrometric analysis, we calculate that the mature toxin has a mass of 88.2 ± 0.2 kDa and consists of approximately 821 amino acids.