The subunit S1 is important for pertussis toxin secretion.

Area of Science:

• Microbiology
• Molecular Biology
• Protein Biochemistry

Background:

• Pertussis toxin (PT) is a multi-subunit protein produced by Bordetella pertussis.
• PT consists of an enzymatically active A monomer and a B oligomer responsible for binding to host cells.
• The assembly and secretion pathway of PT are not fully understood.

Purpose of the Study:

• To investigate the role of individual subunits in the secretion of pertussis toxin.
• To identify factors influencing the extracellular release of the B oligomer and the holotoxin.

Main Methods:

• Analysis of Bordetella pertussis mutants with altered S1 subunit.
• Assessment of pertussis toxin subunit assembly and secretion into the culture medium.
• Characterization of S1 protein conformation and degradation in the periplasm.

Main Results:

• Four B. pertussis mutants were identified that secrete low amounts of the B oligomer.
• These mutants possess altered S1 subunits, preventing holotoxin assembly.
• Altered S1 proteins appear to be degraded within the periplasm.

Conclusions:

• The assembled B oligomer contains the necessary structural information for extracellular export of pertussis toxin.
• The S1 subunit is essential for the efficient release of the holotoxin into the culture medium.
• Periplasmic degradation of unassembled S1 may regulate toxin secretion.