PP5: the TPR phosphatase

Abstract

PP5 is unique among protein serine/threonine phosphatases in containing an amino-terminal TPR domain that functions both to maintain low basal activity and to bind to target proteins. Although PP5 can be activated by partial proteolysis or long-chain fatty acyl compounds in vitro, the physiological mechanisms activating this ubiquitous okadaic acid-sensitive protein phosphatase remain unknown. We review the biochemistry and biology of PP5 with an emphasis on putative target proteins. The first genetic studies of PP5 in model organisms are also discussed, as are antisense approaches to determining its function in cultured human cells.