Benjamin Spiller
Last active: 2/25/2021

The E3 ubiquitin ligase- and protein phosphatase 2A (PP2A)-binding domains of the Alpha4 protein are both required for Alpha4 to inhibit PP2A degradation.

LeNoue-Newton M, Watkins GR, Zou P, Germane KL, McCorvey LR, Wadzinski BE, Spiller BW
J Biol Chem. 2011 286 (20): 17665-71

PMID: 21454489 · PMCID: PMC3093842 · DOI:10.1074/jbc.M111.222414

Protein phosphatase 2A (PP2A) is regulated through a variety of mechanisms, including post-translational modifications and association with regulatory proteins. Alpha4 is one such regulatory protein that binds the PP2A catalytic subunit (PP2Ac) and protects it from polyubiquitination and degradation. Alpha4 is a multidomain protein with a C-terminal domain that binds Mid1, a putative E3 ubiquitin ligase, and an N-terminal domain containing the PP2Ac-binding site. In this work, we present the structure of the N-terminal domain of mammalian Alpha4 determined by x-ray crystallography and use double electron-electron resonance spectroscopy to show that it is a flexible tetratricopeptide repeat-like protein. Structurally, Alpha4 differs from its yeast homolog, Tap42, in two important ways: 1) the position of the helix containing the PP2Ac-binding residues is in a more open conformation, showing flexibility in this region; and 2) Alpha4 contains a ubiquitin-interacting motif. The effects of wild-type and mutant Alpha4 on PP2Ac ubiquitination and stability were examined in mammalian cells by performing tandem ubiquitin-binding entity precipitations and cycloheximide chase experiments. Our results reveal that both the C-terminal Mid1-binding domain and the PP2Ac-binding determinants are required for Alpha4-mediated protection of PP2Ac from polyubiquitination and degradation.

© 2011 by The American Society for Biochemistry and Molecular Biology, Inc.

MeSH Terms (17)

Adaptor Proteins, Signal Transducing Amino Acid Motifs Animals Binding Sites Crystallography, X-Ray HEK293 Cells Humans Intercellular Signaling Peptides and Proteins Intracellular Signaling Peptides and Proteins Mice Molecular Chaperones Phosphoproteins Protein Phosphatase 2 Protein Structure, Tertiary Ubiquitin Ubiquitin-Protein Ligases Ubiquitination

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