Characterisation of a novel Drosophila melanogaster testis specific PP1 inhibitor related to mammalian inhibitor-2:: identification of the site of interaction with PP1

A novel Drosophila melanogaster protein, termed inhibitor-t, that bears 41% sequence similarity to human protein phosphatase inhibitor-2 has been identified using human protein phosphatase 1 (PP1) in the yeast two hybrid system. Inhibitor-t mRNA is detected in adult males, larvae and pupae and the 184 amino acid thermostable protein located only in testis, The gene for inhibitor-t maps to cytological location 86F1 on the third chromosome. Bacterially expressed inhibitor-t specifically inhibits both mammalian and D, melanogaster PP1 catalytic subunits with an IC50 Of approximately 200 nM, A motif -FEX1X2RK-, conserved between inhibitor-t, inhibitor-2 and its Saccharomyces cerevisiae homologue Glc8, is demonstrated to be required for binding to PP1. (C) 1998 Federation of European Biochemical Societies.