Figure 7. Schematic of possible modes of Pcdh-mediated recognition.
(A) Pcdhs form homophilic and/or heterophilic cis-dimers, which are thought to be the recognition unit. (B) One possible Pcdh recognition complex is a dimer-of-dimers, which has been observed in solution for homophilic complexes of β, γB, and some C-type Pcdhs (Table 2). In this model the specificity of the trans-interaction would require both arms of the cis-dimer to match for recognition (Rubinstein et al., 2015). (C) An alternative recognition complex that has been proposed is a linear zipper (Rubinstein et al., 2015). In this model only one arm of opposing cis-dimers needs to match to join the assembly, but incorporation of a dimer containing an isoform that is not expressed by the opposing cell would terminate growth of the intercellular Pcdh zipper.