Fig. 2.

The unique spaCBA pili cluster of L. rhamnosus GG and its expression. (A) Schematic illustration of the spaCBA and spaFED gene clusters. Depicted are the sortase (dark gray arrows), pilin subunits (white arrows), Cna protein B-type domain (gray), E box (black), YPKN pilin-like motif (black diagonal stripes), LPXTG-like motif (light gray arrowheads), and secretion signal (light gray). The von Willebrand type A domain is indicated by black and gray vertical stripes. The best homology match between proteins (gray arrows) and % amino-acid identity are indicated. (B) Detection of cell wall-associated proteins by immunoblotting. E. coli-purified SpaC (lane 1), cell wall protein extracts of strains GG-ΩspaC (lane 2), GG (lane 3), and LC705 (lane 4) were prepared from cells grown in Man–Rogosa–Sharpe broth, separated by SDS/PAGE, electroblotted to a membrane, and probed with SpaC antiserum. The positions of the monomeric SpaC protein (*), HMW protein complexes, and molecular weight standards (kDa) are indicated.