TPR arrays

Currendy available crystal structures of TPR arrays show a highly homologous picture for three tandem repeats among unrelated TPR proteins and significant structural similarity to a distantly related protein family, the 14-3-3 helical repeat proteins (Das et al., 1998 Scheufler et al., 2000). Although structures of a TPR protein in both the free and ligand-bound... 

Tfc4 also interacts directly with the Bdpl subunit of TFIIIB (Dumay-Odelot et al., 2002 Ruth et al., 1996), and this interaction, like that for Brfl, involves both TPR arrays (Ishiguro et al., 2002 Liao et al., 2003 ... 

A TPR structure-based phylogenetic analysis of TPRsl-9 in Tfc4 has identified the invariant and highly conserved residues in each TPR array that are not involved in generating the TPR fold (Moir et al., 2002b). These residues are evenly distributed between the A and B helices in... 

A, Identification of Potential Ligand Binding Sites in the TPR Arrays of Tfc4... 

The potential sites of ligand binding identified by this analysis indicate that interactions with the two TPR arrays of Tfc4 involve a mode of binding that is distinct from the carboxylate clamp described for the Hop TPR-ligand complexes (Scheufler et al., 2000). 

In the peroxisomal importer protein, PEX5, the seven consecutive TPRs do not form an extended superhelix but separate into two TPR arrays, each composed of three repeats. These arrays are oriented antiparallel to one... 

Third, as noted earlier, the interaction between Brfl and the TPR arrays in Tfc4 is likely to sterically block Bdpl binding to this same region, and thus, Brfl must be displaced from this site to allow Bdpl recruitment. 

Fifth, the recruitment of Bdpl proceeds via contacts in both TPR arrays (as indicated by biochemical studies and the effects of ATPR2 and mutations in TPR7). 

Tfc4 also binds other components of the Pol III transcription apparatus, although a requirement for the TPR arrays and, in particular, specific residues in the TPR channels has been reported for only some of these interactions. 

Last, understanding the complex mechanism by which Tfc4 interacts with TFIIIB subunits may provide a paradigm for understanding how multiple TPR arrays contribute to the assembly and function of multisubunit complexes. 

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