CsrA induces expression of plasmid-encoded fimbriae by binding the pefA 50-UTR Since the substantial PefA expression was CsrA dependent , we wanted to study the mechanism by which CsrA activates expression of plasmid-encoded fimbriae .
These data suggested that CsrA bound specifically to a single GGA binding site in the pefA 50-UTR .
To further investigate whether binding of CsrA to the GGA motif in the pefA 50-UTR was required for expression of plasmid-encoded fimbriae , we introduced point mutations into the Figure 3 CsrA regulates expression of PefA .
The CsrA-binding site in the pefA 50-UTR controls expression of plasmid-encoded fimbriae in-vivo A possible biological-function for the hierarchical control of fimbrial expression would be to ensure that S. typhimurium does not express plasmid-encoded fimbriae while residing outside a host .