ptxA
Domain
The region which spans amino acids 42-49 is required for enzymatic activity and contributes to the formation of a potentially important antigenic determinant.
Function
S1 is an NAD-dependent ADP-ribosyltransferase, which plays a crucial role in the pathogenesis of B.pertussis causing disruption of normal host cellular regulation. It catalyzes the ADP-ribosylation of a cysteine in the alpha subunit of host heterotrimeric G proteins. In the absence of G proteins it also catalyzes the cleavage of NAD(+) into ADP-ribose and nicotinamide. It irreversibly uncouples the G-alpha GTP-binding proteins from their membrane receptors.
Sequence Similarities
Belongs to the bacterial exotoxin subunit A family.
Cellular localization
- Secreted
- The individual chains are secreted by a sec-dependent mechanism into the periplasm. Then, S1 associates with the outer membrane before it joins with the B subunit to form the secretion-competent holotoxin. The type IV secretion system ptl mediates secretion of assembled toxin through the outer membrane.
Alternative names
BP3783, ptxA, Pertussis toxin subunit 1, PTX S1, Islet-activating protein S1, NAD-dependent ADP-ribosyltransferase, IAP S1