Fig. 1. Sequence alignment of T. brucei SRP19 with its homologues. (A) The alignment was performed using the ClustalW multiple sequence alignment program (http://npsa-pbil.ibcp.fr/cgi-bin/npsa_automat.pl?page=/NPSA/npsa_clustalwan.html). Residues red, green and blue represent identity, similarity and weak similarity, respectively. Pink represents residues that are conserved between trypanosome species. Red circles indicate indirect contact sites between SRP19 and helix 6 that are conserved in M. jannaschii and H. sapiens. Blue squares represent indirect contact sites between M. jannaschii SRP19 and helix 8. Secondary structure elements are shown underneath the sequence. The sequences were obtained from the following sources: TbSRP19, T. brucei, GeneDB acc. no. Tb10.1560; TcSRP19, T. cruzi, GeneDB acc. no. Tc00.1047053511281.59; LmSRP19, L. major, GeneDB acc. no. LmjF19.1600; HsSRP19, Homo sapiens, TrEMBL acc. no. P09132; MjSRP19, M. jannaschii, TrEMBL acc. no. Q58440. (B) Schematic representation of the T. brucei SRP S domain. The sequence of the 7SL RNA S domain is from Michaeli et al. (Michaeli et al., 1992). The helices and loops are designated by H and L, respectively, and their numbers are indicated.