This family consists of several eukaryotic proteins that are thought to be involved in the regulation of glycogen metabolism. For instance, the mouse PTG protein has been shown to interact with glycogen synthase, phosphorylase kinase, phosphorylase a: these three enzymes have key roles in the regulation of glycogen metabolism. PTG also binds the catalytic subunit of protein phosphatase 1 (PP1C) and localizes it to glycogen. Subsets of similar interactions have been observed with several other members of this family, such as the yeast PIG1, PIG2, GAC1 and GIP2 proteins. While the precise function of these proteins is not known, they may serve a scaffold function, bringing together the key enzymes in glycogen metabolism. This family is a carbohydrate binding domain.