Three-dimensional structure of the catalytic subunit of protein serine/threonine phosphatase-1

Abstract

The crystal structure of mammalian protein phosphatase-1, complexed with the toxin microcystin and determined at 2.1 A resolution, reveals that it is a metalloenzyme unrelated in architecture to the tyrosine phosphatases. Two metal ions are positioned by a central beta-alpha-beta-alpha-beta scaffold at the active site, from which emanate three surface grooves that are potential binding sites for substrates and inhibitors. The carboxy terminus is positioned at the end of one of the grooves such that regulatory sequences following the domain might modulate function. The fold of the catalytic domain is expected to be closely preserved in protein phosphatases 2A and 2B (calcineurin).

Zinc binds to and directly inhibits protein phosphatase 2A in vitro

“…Further, among the three GSTtagged PP2Ac truncates, PP2Ac (51-270) had the highest phosphatase activity (Fig. 3A), consistent with previous speculation that the catalytic activity of PP2A is located on this segment [20] . In addition, Zn 2+ signifi cantly inhibited the PP2Ac (51-270) activity (Fig.…”

“…To further reveal the underlying mechanism, we cut PP2Ac into several segments and then tested their interactions with Zn 2+ using a Zn 2+ -IDA-agarose affinity binding assay. The crystal structure of the PP2A catalytic subunit is not known, however, based on the threedimensional structure of the PP-1 catalytic subunit, which has a catalytic domain highly homologous with PP2A, the PP2Ac (51-270) segment is thought to cover the catalytic active site and metal coordination center [20] . Furthermore, Wozniak et al reported that the motif of amino-acids 50-270 of PP2Ac contains active site with high affi nity with divalent cations [29] .…”

“…As a metal ion, Zn 2+ has been reported to tightly bind to PP2B [26] and directly inhibit the activity of λ Ser/Thr phosphoprotein phosphatase [27] ; both phosphatases share sequence identity in the catalytic domain with PP2A [20] . So is it possible that Zn 2+ also has a direct effect on PP2A?…”

Involvement of protein phosphatase 2A nuclear accumulation and subsequent inactivation of activator protein-1 in leptomycin B-inhibited cyclin D1 expression

“…PP1 consists of a catalytic subunit (PP1c) associated with various regulatory subunits, forming numerous oligomeric enzymes (Wera and Hemmings, 1995;Campos et al, 1996). PP1c and PP2Ac are 67% homologous and most of the amino acids crucial for the three-dimensional structure of PP1c are conserved in PP2Ac (Goldberg et al, 1995). Although OA inhibited PP1 at low concentrations (o100 nM) in vitro, it failed to inhibit PP1 but not PP2A up to 1 mM in cultured cells (Favre et al, 1997).…”

Multiple Toxin Production in the Cyanobacterium Microcystis: Isolation of the Toxic Protease Inhibitor Cyanopeptolin 1020

“…5 Cyanopeptolin SS isolated from a natural cyanobacterial bloom caused death of crustaceans 6 as did oscillapeptin J for Thamnocephalus platyurus. 7 While little is known about the toxicity of cyanopeptolins, the most studied cyanobacterial toxins are the microcystins, which exert their hepatotoxicity through protein phosphatase inhibition 8 and are produced by species of the genera Microcystis, Anabaena, Oscillatoria, Planktothrix, and Nostoc. Microcystins are suspected of countless animal poisonings throughout the globe and also thought to be responsible for a severe incident in Brazil, where several persons died of contaminated water.…”