One repeat of the cell wall binding domain is sufficient for anchoring the Lactobacillus acidophilus surface layer protein

The N-terminal repeat (SAC1) of the S-protein of Lactobacillus acidophilus bound efficiently and specifically to cell wall fragments (CWFs) when fused to green fluorescent protein, whereas the C-terminal repeat (SAC2) did not. Treatment of CWFs with hydrofluoric acid, but not phenol, prevented binding. Apparently, SAC1 is necessary and sufficient for cell wall binding. Our data suggest that SAC anchors the S-protein to a cell wall teichoic acid.