Several in‐frame linker insertions have been made in various positions in the faeG gene encoding the K88ab fimbrial subunit protein from porcine enterotoxigenic Escherichia coli. The effects of the linker insertions have been investigated with regard to the ability of the mutated fimbrial subunits to be exported to the surface of the bacterial cell and assembled into a fimbrial structure. The structure/function relationship of the subunit protein is discussed in the light of the phenotypes of the mutations constructed, secondary structure predictions, and hydrophilicity plots.