T. brucei ALPH1.

(A) Alignment of the signature motifs of a classical eukaryotic PPP (TbPP1, Tb927.4.3560) and the atypical PPPs ApaH of E. coli and ALPH1 of T. brucei. The three catalytic signature motifs of PPPs are framed. The two changes in the GDXXDRG motif that are characteristic for ApaH and Alph are highlighted in red. In Alph’s and ApaH, the second aspartate is replaced by a neutral amino acid (n). In most Alphs, but not in ApaH or other PPPs, arginine, a coordinator of phosphate [72], is replaced by lysine [41]. (B) Structure of diadenosine tetraphosphate (top) and of the mRNA cap of trypanosomes (bottom). The differences are marked in red. (C) Domain structure of ALPH1 and conservation between the different kinetoplastida orthologues. All available kinetoplastid orthologues to TbALPH1, (13 sequences of trypanosomes, 1 of Leptomonas and 6 of Leishmania strains) were aligned by ClustalW using default parameters. The minimal % identity between any two sequences is indicated for the three different ALPH domains. The sequences of trypanosomes and Leishmania/Leptomonas were also analysed separately.