<p>These eukaryotic serine/threonine phosphoprotein phosphatases, first described from human (PP5) and <taxon tax_id="4932">Saccharomyces cerevisiae</taxon> (PPT1), are distinguished from related protein phosphatases by anN-terminal region of about 200 residues that contains three tandem tetratricopeptide repeats (TPR) [<cite idref="PUB00014443"/>]. Structurally, TPR repeats form a helical scaffold of antiparallel alpha-helices with anamphipathic groove that mediates protein-protein interactions [<cite idref="PUB00001313"/>]. The TPR domainscontribute to regulation of PP5 activity, which is normally low but stimulated by interaction with lipid [<cite idref="PUB00014413"/>], and to interaction with other proteins [<cite idref="PUB00014441"/>].</p>