Multiple sequence alignment and prediction of the structure of Hel45.

<p>(A) Multiple sequence alignment of the diagnostic conserved region of the DEAD-box helicase family (positions 25–365 according to Hel45). The nine putative conserved motifs (<i>Q</i>, <i>I</i> (WalkerA), <i>Ia, Ib, II</i> (WalkerB), <i>III, IV, V, VI</i>) are marked with orange boxes. Alignment columns displaying 100%, more than 90%, and more than 80% of similarity are highlighted in black, dark grey, and light grey, respectively. Sequences are identified with organism abbreviation and gene name, except Hel45. The organism abbreviations are: Sc: <i>Saccharomyces cerevisiae</i>, Hs: <i>Homo sapiens</i>, Pf: <i>Plasmodium falciparum</i>. The sequences have the following GenBank Identifiers (GIs): Hel45 (71418343), Sc_TIF2 (6322323), Sc_FAL1 (398365053), Sc_DBP5 (6324620), Hs_EIF4A1 (4503529), Hs_EIF4A2 (83700235), Hs_EIF4A3 (7661920), Hs_DDX19A (8922886), Pf_PFD1070w (124505577), Pf_H45 (124810293), Pf_DBP5 (6324620). (B) Schematic representation showing the nine conserved helicase motifs are boxed in orange. The N-terminal domain (NTD) contains the motifs Q, I and II for ATP-binding, Ia and Ib for RNA-binding, and III for ATP hydrolysis <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0109521#pone.0109521-Cordin1" target="_blank">[44]</a>. The C-terminal domain (CTD) contains the motifs IV and V for RNA-binding, and VI for ATPase and unwinding activities <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0109521#pone.0109521-Cordin1" target="_blank">[44]</a>. The predicted nuclear export signal (NES) in the LYDTLTI sequence (255–261 position) is shown in yellow. (C) Molecular modeling of Hel45. The nine motifs are highlighted in orange, the predicted NES (yellow) is close to the CT extremity (green). A zoom of this region (box) shows the side chains of amino-acids D257, T258 and D393, and the interactions that maintain the structure at its C-terminal extremity. The organization of the NES in the CT is shown in the inset (upper right corner).