Fig 6.

Heterologous expression of CofA in Vibrio cholerae. (A) Immunoblot showing CofA in whole-cell culture of wild-type ETEC 31-10 and V. cholerae (Vc) JR003, in which the gene segment encoding the mature TcpA was replaced with the corresponding cofA gene fragment within the tcp operon. CofA from both strains ran at the expected molecular mass of the processed pilin (calculated molecular mass, 21.6 kDa) rather than the unprocessed prepilin (calculated molecular mass, 25.3 kDa). Negative controls: ETEC 31-10p, which lacks the cof operon; V. cholerae O395, the parental strain for JR003. An immunoblot for DnaK (shown below) served as a loading control. (B) Immunoblot analysis of whole-cell supernatants, indicating the presence of intact CFA/III filaments in ETEC 31-10 but not V. cholerae JR003.