This approach has already been used to identify DExD/H helicases in human, yeast, rice, Entamoeba histolytica, Plasmodium falciparum, Leishmania major, Trypanosoma cruzi and Trypanosoma brucei (Table 1). The relationship between the number of DEAD-box and DExH-box helicases supports our finding of 22 DEAD-box and 10 DExH-box (6 DEAH-box and 4 Ski2-like) in Giardia. Multiple sequence analysis generated a phylogenetic tree, showing the evolutionary separation of these six families (DEAD-box,

DEAH-box, Ski2, RecQ, Rad3, and Swi2/Snf2) (see Additional file 3: Figure S1). Table 1 Number of putative DExD/H-box RNA helicases in other organisms Organism DExD/H helicase family (Reference) DEAD-box DExH-box* Giardia lamblia 22 10   Homo sapiens 42 18 [30] Oryza Selleck GDC0449 sativa 26 8 [31] Saccharomyces cerevisiae 26 12 [32] Entamoeba histolytica 20 13 [33] Plasmodium falciparum 22 ND [34] Leishmania major 28 18 [35] Tripanosoma cruzi 30 19 [35] Tripanosoma brucei 27 19 [35] * DEAH-box and Ski2-like families. BLASTP analyses of CX-5461 manufacturer the 46 G. lamblia SF2 helicases within the NCBI

Human LGX818 molecular weight database presented the following ranges of identity and similarity, respectively: DEAD-box family (23–47% and 39–69%); DEAH-box family (26–39% and 42–54%); Ski2 family (28–43% and 47–63%); Swi2/Snf2 family (25–39% and 41–58%); RecQ family (25–32% and 41–50%); Rad3 family (27–35% and 47–51%). The unique UPF1 sequence presents 39% identity and 52% similarity to human UPF1. The yeast RNA helicase homologs, their predicted protein function and other features are cAMP also included in Additional file 4: Table S3 for each helicase identified

in G. lamblia. The high sequence similarity between putatives RNA helicases from Giardia and the characterized homologous proteins suggest that they may have a similar function in RNA metabolism. The DEAD-box family The 22 sequences identified from this family were aligned for further analysis and the nine consensus motifs described in DEAD-box RNA helicases from other organisms were found. The Open Reading Frame (ORF) GL50803_34684 lacks the N-terminal region including the Q Motif; when we performed a new database search, we found that the homologous gene GL50581_3622 from Assemblage B, isolate GS, possesses the complete N-terminal region. Thus, we used this region to search the isolate WB genome database and found the missing region at the CH991776, location 21991–22645. The final gene location was at the CH991776, 21991 – 23994 (+), and the gene coded for a 667-amino acid protein with all the nine consensus motifs of the DEAD-box subfamily, including the Q motif. This motif contains nine amino acids, which is a distinctive and characteristic feature of the DEAD-box family of helicases, and can interact with Motif I and a bound ATP [36].