FIGURE 7.

Proposed model for cadherin junction assembly. (A) Cadherins rapidly bind via their outer domains and kinetically discriminate between different cadherins (shaded and open). Differences in the binding kinetics of different classical cadherins may provide the kinetic proofreading that underlies selective cadherin binding. (B) Once the proteins engage, the cell membranes are held in close proximity sufficiently long for the slower, strong bonds to form between overlapping proteins. In this staged cadherin junction assembly, the sequence of binding events is governed by the hierarchy of kinetic rates.