Fig. 1.

Studying the ClfA–Fg interaction. (A) The N-terminal signal sequence (S) is followed by subdomains N1, N2, and N3 comprising the ligand-binding A region. At the junction between N2 and N3 is found a binding trench in which the ligand (red) inserts and is locked in place. A flexible serine-aspartate repeat region links region A to the C-terminal Wall (W) spanning region and the sorting sequence. The LPXTG motif allows anchoring of the protein to cell-wall peptidoglycan by sortase A. (B) Optical microscopy images of S. aureus bacteria expressing or not full-length ClfA [ClfA⁽⁺⁾ and ClfA⁽⁻⁾ cells] following incubation with Fg-conditioned substrates. (C) Force nanoscopy of the ClfA–Fg interaction: (Left) SCFS; (Right) SMFS. For clarity, the N1 domain of ClfA is not shown.