General questions:
What is the difference between the different classes of secretion complexes? How is B. pertussis secretion complex different from other type IV secretion complexes? When did the secretion complex evolve? Are there any other bacteria that have a similar secretion system?
Secretion complex:
What are all the different proteins involved in the secretion complex? How many copies of each protein are present in the complex? How do they interact with one another? What do all of the different proteins in the secretion complex do? How does the complex open the pore in the outer membrane? How does the secretion complex differentiate between fully assembled toxin and toxin subunits? How many secretion complexes are there per bacteria?
Toxin secretion:
Where does the toxin assemble? How does it move through the peptidoglycan layer? Can the complex secrete more than one pertussis toxin at a time? Can other A-B5 toxins be secreted by this complex? Are there any helper proteins that “load” the pertussis toxin onto the secretion complex? How long does it take the complex to secrete the toxin? Why does the toxin have to be fully assembled to be secreted?
Specific questions:
The components of the Bordetella pertussis secretion system PtlA-I are essential for secretion of pertussis toxin across the outer membrane. Pertussis toxin is assembled in the periplasmic region, between the peptidoglycan layer and the outer membrane. The secretion system runs from the peptidoglycan layer through the outer membrane.
 | How does the pertussis toxin interact with the secretion system to allow for transport? |
| What does the crystal structure of the interaction look like? |
| What residues are important on the pertussis toxin for secretion, but have no effect on toxicity? |
PtlC and PtlH both have nucleotide binding regions (the ability to bind an NTP), and their homologous proteins in the secretion system of A. tumefaciens exhibit some ATPase activity when purified. When this region called a WalkerA motif was deleted, no pertussis toxin secretion was detected.
| What is the purpose of the ATP binding ability of PtlC and PtlH? |
| How does this activity ultimately cause toxin secretion? |