Structural and biochemical characterization of human PR70 in isolation and in complex with the scaffolding subunit of protein phosphatase 2A.

Dovega R, Tsutakawa S, Quistgaard EM, Anandapadamanaban M, Löw C, Nordlund P

PLoS ONE 9 (7) e101846 [2014-07-09; online 2014-07-09]

Protein Phosphatase 2A (PP2A) is a major Ser/Thr phosphatase involved in the regulation of various cellular processes. PP2A assembles into diverse trimeric holoenzymes, which consist of a scaffolding (A) subunit, a catalytic (C) subunit and various regulatory (B) subunits. Here we report a 2.0 Å crystal structure of the free B''/PR70 subunit and a SAXS model of an A/PR70 complex. The crystal structure of B''/PR70 reveals a two domain elongated structure with two Ca2+ binding EF-hands. Furthermore, we have characterized the interaction of both binding partner and their calcium dependency using biophysical techniques. Ca2+ biophysical studies with Circular Dichroism showed that the two EF-hands display different affinities to Ca2+. In the absence of the catalytic C-subunit, the scaffolding A-subunit remains highly mobile and flexible even in the presence of the B''/PR70 subunit as judged by SAXS. Isothermal Titration Calorimetry studies and SAXS data support that PR70 and the A-subunit have high affinity to each other. This study provides additional knowledge about the structural basis for the function of B'' containing holoenzymes.

Protein Science Facility (PSF)

PubMed 25007185

DOI 10.1371/journal.pone.0101846

Crossref 10.1371/journal.pone.0101846

pii: PONE-D-14-16276
pmc: PMC4090178
PDB: 4MEW Structure of the core fragment of human PR70