Mechanisms of the scaffold subunit in facilitating protein phosphatase 2A methylation.
The function of the biologically essential protein phosphatase 2A (PP2A) relies on formation of diverse heterotrimeric holoenzymes, which involves stable association between PP2A scaffold (A) and catalytic (C or PP2Ac) subunits and binding of variable regulatory subunits. Holoenzyme assembly is highly regulated by carboxyl methylation of PP2Ac-tail; methylation of PP2Ac and association of the A and C subunits are coupled to activation of PP2Ac. Here we showed that PP2A-specific methyltransferase, LCMT-1, exhibits a higher activity toward the core enzyme (A-C heterodimer) than free PP2Ac, and the A-subunit facilitates PP2A methylation via three distinct mechanisms: 1) stabilization of a proper protein fold and an active conformation of PP2Ac; 2) limiting the space of PP2Ac-tail movement for enhanced entry into the LCMT-1 active site; and 3) weak electrostatic interactions between LCMT-1 and the N-terminal HEAT repeats of the A-subunit. Our results revealed a new function and novel mechanisms of the A-subunit in PP2A methylation, and coherent control of PP2A activity, methylation, and holoenzyme assembly.
McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin, School of Medicine and Public Health, Madison, Wisconsin, United States of America ; Biophysics Program, University of Wisconsin - Madison, Madison, Wisconsin, United States of America.
Vitali
V
Stanevich
McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin, School of Medicine and Public Health, Madison, Wisconsin, United States of America.
Aiping
A
Zheng
McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin, School of Medicine and Public Health, Madison, Wisconsin, United States of America.
Feng
F
Guo
McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin, School of Medicine and Public Health, Madison, Wisconsin, United States of America.
Li
L
Jiang
McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin, School of Medicine and Public Health, Madison, Wisconsin, United States of America.
Nathan
N
Wlodarchak
McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin, School of Medicine and Public Health, Madison, Wisconsin, United States of America ; Biophysics Program, University of Wisconsin - Madison, Madison, Wisconsin, United States of America.
Yongna
Y
Xing
D015153:Blotting, Western; D002151:Calorimetry; D020134:Catalytic Domain; D031541:Fluorescence Resonance Energy Transfer; D006367:HeLa Cells; D020035:Holoenzymes / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D008745:Methylation; D008958:Models, Molecular; D011487:Protein Conformation; D011497:Protein O-Methyltransferase / Q000378:metabolism; D054648:Protein Phosphatase 2 / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D021122:Protein Subunits; D055672:Static Electricity
D020035:Holoenzymes; D021122:Protein Subunits; C524761:LCMT1 protein, human; D011497:Protein O-Methyltransferase; D054648:Protein Phosphatase 2