Scientific Publications by FDA Staff

Infect Immun 2004 Sep;72(9):5365-72

Analysis of subassemblies of pertussis toxin subunits in vivo and their interaction with the ptl transport apparatus.

Burns DL, Fiddner S, Cheung AM, Verma A

Burns DL, CBER, US FDA, HFM 434, Lab Resp & Special Pathogens, Bldg 29,Room 130,8800 Rockville Pike, Bethesda, MD 20892 USA CBER, US FDA, HFM 434, Lab Resp & Special Pathogens, Bethesda, MD 20892 USA

Pertussis toxin (PT) has an AB(5) structure that is typical of many bacterial protein toxins; however, this toxin is more complex than many toxins since it is composed of five different subunit types, subunits S1 to S5. Little is known about how PT assembles in vivo and how and when it interacts with its secretion apparatus, known as the Ptl transporter. In order to better understand these events, we expressed subsets of the genes encoding the S1, S2, and/or S4 subunits of PT in strains of Bordetella pertussis that either did or did not produce the Ptl proteins. We found evidence to suggest that certain subassemblies of the toxin, including subassemblies consisting of the S1 subunit and incomplete forms of the B oligomer, can form in vivo, at least transiently. These results suggest that the B oligomer of the toxin does not need to completely form before interactions between the S1 subunit and B-oligomer subunits can occur in vivo. All subassemblies localized primarily to the membrane fraction of the cell. Moreover, we found that Ptl-mediated secretion occurs in a strain that produces S1 and an incomplete complement of B-oligomer subunits. These results indicate that subassemblies of the toxin consisting of the S1 subunit and a partial B oligomer can interact with the Ptl system.