Studies on functions of the 63-kDa A- and 74-kDa B'(delta)-regulatory subunits in human erythrocyte protein phosphatase 2A: dissociation and reassociation of the subunits.
A heterodimeric form, CA, of protein-serine/threonine phosphatase (PP) 2A purified from human erythrocytes was dissociated into a 34-kDa catalytic subunit C and 63-kDa inactive subunit A by Sephacryl S-200 gel filtration in the presence of 6 M urea. Reassociation of the C- and A-subunits in the absence of urea suppressed the PP activity of the C subunit toward phosphorylase a, P-H2B histone, and P-H1 histone in the presence or absence of 20 mM MnCl(2) or 50 mM Mg(CH(3)COO)(2), but stimulated the PP activity toward P-H1 histone in the presence of 200 mM NaCl and the Mn(2+)-dependent protein-tyrosine phosphatase (PTP) activity toward P-Tyr-Glu copolymers. The 74-kDa inactive B'(delta) subunit was isolated from a heterotrimeric form, CAB'(delta), of PP2A partially purified from human erythrocytes, by heparin-Sepharose column chromatography. The B'(delta) subunit reassociated with CA and suppressed the PP- and PTP-activities of CA. The B'(delta) subunit did not associate with the isolated C subunit directly, and had no effect on the activities of the C subunit, indicating that the A subunit is essential for the association of the B'(delta) subunit with CA and the resulting suppression of the PP- and PTP-activities.
Inoue
R
R
Department of Biochemistry, Hiroshima University School of Medicine, Minami-ku, Hiroshima, 734-8551, Japan.
Usui
H
H
Tanabe
O
O
Nishito
Y
Y
Shimizu
M
M
Takeda
M
M
D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D004912:Erythrocytes / Q000201:enzymology*; D006801:Humans; D008345:Manganese / Q000378:metabolism; D008970:Molecular Weight; D010446:Peptide Fragments / Q000502:physiology*; D010749:Phosphoprotein Phosphatases / Q000737:chemistry*; D011487:Protein Conformation; D054648:Protein Phosphatase 2
D010446:Peptide Fragments; D008345:Manganese; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2