TFIIIB Subunit Bdp1 Participates in RNA Polymerase III Transcription in the Protozoan Parasite Leishmania major
Figure 1
Sequence and structure analyses of the extended SANT and N-linker domains from LmBdp1. (a) Multiple sequence alignment of the N-linker and extended SANT domains from L. major (Lm), T. brucei (Tb), T. cruzi (Tc), A. thaliana (At), D. melanogaster (Dm), S. cerevisiae (Sc), M. musculus (Mm), and H. sapiens (Hs). Identical residues in all species are indicated by black shading. Conserved substitutions are denoted by dark-grey shading with white lettering and semiconserved substitutions are indicated by light-grey shading with black lettering, according to the Clustal Ω program. Trypanosomatid-specific conserved residues are shaded in red with white letters. Conserved amino acids in at least three species different from trypanosomatids (At, Dm, Sc, Mm, and Hs) are shaded in blue with white lettering. In the N-linker, aromatic residues are denoted in bold. Below the Hs sequence, the hash characters (#) indicate conserved residues that interact with the DNA minor groove (Y291, S293, F294, and Y299 in human Bdp1). The percent sign (%) indicates highly conserved amino acids (W303, E307, and R332 in human Bdp1) involved in the interaction between the N-linker and the extended SANT domain. The triangle symbol (▲) shows the invariably conserved R334 that forms a salt bridge with residue E191 from TBP and also interacts with the template DNA strand. Asterisks () indicate conserved amino acids K338, N339, K342, R343, and E345 that contact both faces of the major groove of the DNA. Symbols above the Lm sequence indicate conserved residues in LmBdp1. Predicted α-helices are denoted by rectangles (H1 to H5) for LmBdp1 (above the alignment) and human Bdp1 (below the alignment). (b) Predicted three-dimensional structure of the N-linker and extended SANT domain of LmBdp1 by homology-modeling using the crystal structure of human Bdp1 (HsBdp1) as a template. The colors of the five α-helices are conserved in panels (a) and (b).