Figure 4.

Schematic representation of the structure of PDX family proteins. Besides the PDX domain, PNPases contain extra domains at both termini: a highly conserved N-terminal domain of unknown function, and two C-terminal RNA-binding domains, KH and S1. Both KH and S1 RNA-binding domains are highly conserved among PNPases. Other PDX family members (RPH homologs) normally contain only a single highly-conserved PDX domain characterized by three conserved sequence motifs. The sequence patterns of these three motifs are shown including some specific patterns for subfamilies. The syntax of the patterns follows that used in PHI-BLAST searches (http://www.ncbi.nlm.nih.gov/BLAST/pattern.html). Those residues conserved in >80% of the analyzed sequences are shown in bold type.