Spontaneous and chaperone-assisted metal loading in the active site of protein phosphatase-1.

Protein phosphatase PP1 has two active-site metals (Zn ²⁺ /Fe ²⁺ ) that are essential for catalysis. However, when expressed in bacteria, PP1 has two Mn ²⁺ -ions in its active site, indicating that the incorporation of Zn ²⁺ /Fe ²⁺ depends on additional eukaryotic component(s). Here, we used purified, metal-deficient PP1 to study metal incorporation. Fe ²⁺ was incorporated spontaneously, but Zn ²⁺ was not. Mn ²⁺ -incorporation at physiological pH depended on the co-expression of PP1 with PPP1R2 (Inhibitor-2) or PPP1R11 (Inhibitor-3), or a pre-incubation of PP1 at pH 4. We also demonstrate that PPP1R2 and PPP1R11 are Zn ²⁺ -binding proteins but are, by themselves, not able to load PP1 with Zn ²⁺ . Our data suggest that PPP1R2 and PPP1R11 function as metal chaperones for PP1 but depend on co-chaperone(s) and/or specific modification(s) for the transfer of associated Zn ²⁺ to PP1.
(© 2024 The Author(s). FEBS Letters published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies.)