Schematic representation of FHA and model proteins used in this work.

<p>(A) Model of FHA. The dotted vertical lines at the right side of the protein model indicate the approximate lengths of Fha60 and Fha30, which both have the same N-terminus as full-length FHA. The TPS domain is shown in blue, the R1 region is shown in red, and the B1, R2 and B2 domains are shown in green, magenta and cyan, respectively. The X-ray structure of Fha30 is known, while the R1 and R2 regions were built by using the models reported in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0073572#pone.0073572-Kajava3" target="_blank">[18]</a>, and the B1 and B2 regions were built by molecular modeling using the I-TASSER web server <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0073572#pone.0073572-Roy1" target="_blank">[19]</a>. (B) Conserved regions of Fha30. On the basis of multiple sequence alignments, four regions of different conservation rates were identified in the TPS domain. The most conserved subdomains C1 and C2 are shown in dark blue, and the less conserved subdomains LC1 and LC2 are shown in light blue. The first R1 coils are in red. (C) Structural organization of Fha30. The N-terminal cap and the six successive coils (Coil_A to Coil_F) of the TPS domain are shown in magenta, blue, cyan, green, yellow, orange and brown, respectively. The three R1 coils present in the crystal structure of Fha30 are shown in dark red, red and pink, and the three extra-helical elements are shown in grey. Elements II and III assemble together to form a four-stranded βsheet that packs against the β-helical core formed by coils_A to _F.