SINGLEMOLECULE FORCE SPECTROSCOPY OF MICROBIAL CELL ENVELOPE PROTEINS - Life at the Nanoscale: Atomic Force Microscopy of Live Cells - page 320

C-terminal, lysine-rich region and anionic aspartates/glutamates of the
protein.

(b)

(a)

(c)

Figure 15.5. SMFS of the HBHA-HBHA interaction. (a) Surface chemistry used to
measure the forces between HBHA exposing their N-terminal regions. (b) Adhesion
force histogram and representative force curves measured between the N-terminal
domains. Elongation forces were generally well described by the WLC model (red lines).
(c) Similar data were obtained between a tip exposing the HBHA N-terminal region
and living mycobacteria. The inset shows an AFM image of a few mycobacteria.

Homophilic HBHA interactions were also directly measured on the surface
of living mycobacteria ( Fig 15.5c ) . Force curves recorded over the bacterial
surface with a tip exposing N-terminal regions exhibited a distribution
reminiscent of that observed for model surfaces exposing N-terminal tails.
Adhesion forces were therefore attributed to multimer formation due
to speciic coiled-coil interactions. The tip exposing C-terminal regions
also showed binding forces in most areas, but a broader distribution was
observed, suggesting these forces originate from electrostatic interactions.
Adhesion forces were never detected on a bacterial mutant impaired in HBHA
production.