The tetratricopeptide repeat domain provides the concave surface necessitated for SIP recognition. RopB-CTD houses 5 stacked TPR motifs, each having sets of paired antiparallel helices that aid in the formation of a concave inner pathway and a convex exterior. The base of the recognition site is constructed by α6 and α8 helices [See Also: alpha helix], while the supporting walls are constructed from helices α2, and α12. The exterior portion of the recognition site is flanked by asparagines N152 and N192 thus providing a ridge of support for the peptide-protein complex.