Figure 7.

A: Sequence of the LRR domain of LgrE. The different motifs conserved in LRRs are highlighted in colour. Probable events of multimerization and deletion of repeats are indicated by E1 to E7 whose numbering is not chronological. A parcimonous scenario is proposed for the multimerization of the LRRs of LgrE. In the first part of the LRR domain: formation of a unit of three different LRRs (E1) that was later triplicated (E2) by two independent duplications in tandem. Finally, a deletion occurred (E3). On the second part of the LRR domain, a triplicate was build (E7), each member of it were duplicated (E4, E5 and E6). Our model shows that multimerization by adjacent concatenation occurred in LgrE. It also shows that LRR₁^lgrE, LRR₁₁^lgrE, and LRR₁₈^lgrE were not involved directly during this process, suggesting more constrains on their sequences. Furthermore, it points out that the common frame is respected during all duplication events (E1, E2, E3, E5, E6, and E7) except one (E4). Finally, the later event (E4) associated to the deletion (E3) were certainly imposed by structural constrains acting on LRR₁₁^lgrE. B: General scheme of the mechanism of the multimerization of the LRRs of the LGRs.